Export (0) Print
Expand All
32 out of 45 rated this helpful - Rate this topic

Tips and Techniques for Queries in Access 2007

Office 2007

Summary: Learn about queries and their uses in Microsoft Office Access 2007. (29 printed pages)

Luke Chung, President of FMS Inc

August 2009

Apples to: 2007 Microsoft Office System, Microsoft Office Access 2007

Contents

Download the Sample Access Database

Overview

Microsoft Office Access 2007 is the most popular Windows database program. A major reason for its success is its revolutionary query interface. Once data is collected in a database, analysis and updates need to be performed. Queries offer the ability to retrieve and filter data, calculate summaries (totals), and update, move and delete records in bulk. Mastering Microsoft Access queries will improve your ability to manage and understand your data and simplify application development.

The visual representation of tables and the graphical links between them makes Microsoft Access queries extremely easy to use. Fortunately, the nice user interface also allows very powerful and advanced analysis. The entire query engine is modeled on SQL systems and allows switching between the graphical query design and SQL syntax. Many Microsoft Access users and developers learned SQL from this feature.

Knowing the many features of Microsoft Access queries allows you to perform advanced analysis quickly without programming. This presentation covers the basics of queries revealing a variety of subtleties. It quickly moves to more advanced topics with hints and techniques for creating sophisticated queries. Finally, programmatic use of queries is presented.

Query Types

Microsoft Access supports many types of queries. Here is a description of the major categories:

  • Select Queries

    Retrieve records or summaries (totals) across records. Also includes cross-tabulations.

  • Make Table Queries

    Similar to Select Queries but results are placed in a new table.

  • Append Queries

    Similar to Select Queries but results are added to an existing table

  • Update Queries

    Modify data in the records.

  • Delete Queries

    Records are deleted from a table.

Select queries are the most common queries and can be used for viewing and a data source for forms, reports, controls, and other queries. The other queries create or change data and are known collectively as Action queries.

Basic Select Queries

The most basic Select queries retrieve the records you specify from a table. You can choose the fields from a table to display, and specify the criteria for selecting records. In the most cases, while viewing the query results you can modify the data and update the original records. These updateable views are extremely powerful.

Selecting Tables and Fields

The first step in creating a query is to specify the table or tables to use and the fields to display. Selecting tables is simple. Just choose the table from the list when the query is first created or use the Add Table command from the Query menu. The selected table is placed on the upper portion of the query design window. From there you can select the fields for the query by double-clicking on them or selecting several fields (by using Shift-Click or Ctrl-Click) and dragging them to the bottom portion of the query by example (QBE) grid. Make sure that the Show option is checked to display the field.

Sorting and Reordering Fields

Once you place the fields on the QBE grid, you can reorder the fields by clicking the column and dragging it to where you want it. To sort the results, specify the Sort option under the fields to sort. You can choose Ascending or Descending order. Note that you can turn off the Show setting and sort on a field that does not appear in the display.

Renaming Fields

A very nice feature of Microsoft Access queries is the ability to rename fields. You might have your data stored in field names that users do not understand. By using a query expression, you can change the field name the user sees. For example, you can change a field named CustID to Customer ID by placing the new name followed by a colon and the original name in the QBE field cell: Customer ID:[CustID].

Using Calculated Fields (Expressions)

In addition to retrieving fields from a table, a Select query can also display calculations (expressions). Of course, expressions cannot be updated because they do not exist in the original table. Expressions are extremely powerful and allow you to easily display complex calculations. There is an Expression Builder that simplifies the selection of fields and functions. By default, expression fields are named Expr1, Expr2, and so on; therefore, you usually want to rename them to something more understandable.

Setting Query Properties

When you design a query, you can choose View | Properties or right click the top portion of the query and then choose Properties to see and modify the query properties.

Figure 1. Query properties

Query properties

Description

This property lets you provide a description of the query. Use the property to help you remember the purpose of the query.

Default View

Show the results in a datasheet like a table, or a pivot chart or pivot table.

Output All Fields

This option is usually set to No. If it is changed to Yes, all the fields of all the tables in the query are shown. In general, you should leave this property alone and specify the fields desired in the QBE grid.

Top Values

Instead of retrieving all records, you can specify the top n records or n percent, where n is the value specified here.

Unique Values

By default, this is set to No and all records are retrieved. If you change this to Yes, every record retrieved contains unique values (SQL uses the SELECT DISTINCT command). That is, no retrieved records are identical. For example, you can run a query for the State field of the Patient table. With this set to No, the result is a record for each patient. When set to Yes, only the list of unique states is displayed. When set to Yes, the query is not updateable.

Unique Records

By default this is set to No and all records are retrieved. For one-table queries, this property is ignored. For multi-table queries, if it is set to Yes, (similar to using a DISTINCTROW in a SQL statement) only unique records in the underlying tables are retrieved.

The Unique Records and Unique Values properties are linked and only one can be set to Yes (both can be No). When Unique Records is Yes, Unique Values is automatically set to No. When both properties are set to No, all records are returned.

Difference between DISTINCT vs. DISTINCTROW

These options sometimes appear to provide the same results, but there are significant differences.

DISTINCT checks the results of query and eliminates duplicate rows. These queries (Unique Values = Yes) are not updateable. They are a snapshot of your data and don't reflect subsequent data modifications by users. This is similar to running a Totals Query (for example, using a Group By clause).

DISTINCTROW checks all the fields in the table and then eliminates the duplicate rows. The results of a query with DISTINCTROW (Unique Records = Yes) are updateable and reflect changes to retrieved records (but the query does not automatically run again if the data changes to retrieve different rows).

So the difference is that DISTINCT only checks the fields in the results, while DISTINCTROW checks all the fields in the underlying tables. If your query joins several tables and only displays records from one, the DISTINCTROW option lets you view and edit the results.

For more information, see Distinct versus DistinctRow.

SQL Server Properties

There are several properties related to SQL Server tables that are more technical and rarely need to be modified. For more information, refer to the online Help in Microsoft Access.

Filter, Order By, Filter On Load, Order By On Load

Like a form, you can specify the Filter and Order By settings for a query. However, this is usually part of the query's SQL statement. By using the Filter and Order By properties, you have the extra advantage of specifying the Filter On Load and Order By On Load properties to apply them or not.

Subdatasheet Name, Link Fields, and Size

If you want to display a subdatasheet to show a one-to-many relationship between the results in this query with data from another table, you can specify them here. There is a significant performance cost for having subdatasheets, so only add them if you really need them.

Setting Field Properties

In addition to query properties, each field has properties that can be set. Move to a field in the QBE grid and right click. Depending on the field type, different properties are available. The most important properties are for numeric and date fields. You can specify how the fields are formatted when the query is run.

Viewing Results and SQL Equivalent

Once the query is completed, you can view its results by switching from Design to DataSheet view. You can also view the SQL equivalent. You can even edit the SQL syntax directly and view the results and/or switch to Design view.

Setting Criteria

The bottom section of the QBE grid is several rows for Criteria. These are optional entries to specify which records are retrieved. If you want all the Patients from the state of Virginia, just type VA in the State's criteria. To further narrow the scope, you can type criteria for several fields.

Multi-Field Query Criteria

Typing criteria on the same row for several fields performs an AND query between the fields. That is, records that match the criteria in field 1 AND the criteria in field 2, and so on are retrieved. If criteria are placed in different rows, an OR query is performed; that is, retrieve all records matching criteria in field 1 OR criteria in field 2, and so on.

Criteria Types

The simplest type is the exact match. Just type the value desired in the field's criteria section. Remember that by using the Show option to eliminate the field from the display, you can specify criteria in fields the user never sees.

<>, <, >, Between .. And ..

You can also retrieve records where a field does not have a particular value by using < > followed by the value that you don't want. Similarly, you can use >, <, >=, or <= for ranges. To select records with values between two values, use the BETWEEN .. AND .. syntax.

Nulls

To select records with Null values, type Is Null. The opposite is Is Not Null. For text fields, remember that zero length strings ("") are not nulls.

OR and IN(.., .., ..)

To select records where a field can have one of several values, use the OR command. You can simply say: "MD" or "DC" or "VA". Alternatively, the IN command performs the same function; for example, IN("MD", "DC", "VA"). The second syntax is easier if you have many values. Of course, if you have a very large number of values, it is better to keep those values in a table and link your query to it. That is easier to maintain than OR or IN clauses inside queries.

Wildcard Searches

Sometimes, you need to search for a particular letter or digit. Combined with the Like command, you can use wildcards to specify such criteria. Microsoft Access uses the following wildcard characters:

  • ? Single character

  • * Any number of characters

  • # Single digit

  • [..] Character list

  • [!..] Not in character list

For example, if you are interested in a text field where the second letter is "a", the criteria would be: Like "?a*". If you were seeking values where the second letter could be an "a" or "e", the criteria would be: Like "?[ae]*". The opposite of this (all values that do not have "a" or "e" as the second letter) is performed by adding an exclamation point (!) as follows: Like "?[!ae]*". Finally, to select a range of letters (say "a" through "e"), add a dash between the letters: Like "?[a-e]*".

To search for a wildcard character, enclose the value in brackets. For example, to find values that end in a question mark, use this: Like "*[?]"

Advanced Select Queries

Using Parameters

Often it is not possible to know in advance the criteria for a query field. In those cases, where the filter values are not known until runtime, a variable (parameter) can be used. When these queries are run, the user is prompted for the value of each parameter. (The parameters can also be assigned programmatically). Using parameters in queries is extremely powerful and converts static "hard-coded" queries to flexible, dynamic ones. The use of parameters can significantly reduce the number of queries you need, makes queries more useful, and simplifies database maintenance.

It is easy to add parameters. Instead of typing the value of a criterion, type (between the brackets) the prompt that you want the user to see when the query is run. The value that the user types replaces the parameter in the query. In the following example, a parameter [Enter State Name:] is the criteria in the [State] field, and [Enter Minimum Age:] is the parameter in the [Age] field. When this query is run, the user is prompted for the state desired and minimum age, and the records matching that value are retrieved.

Figure 2. Select Query example with two parameters

Select Query example with two parameters

 

Parameters work as long as the parameter definition does not conflict with the field name among the query's tables.

To better define a parameter, you should specify it in the list of parameters. This is an optional step, but there are good reasons to do so. Right-click the top part of the query and choose Parameters. The following form appears; use the form to list each parameter name and each parameter type.

Figure 3. Query Parameters dialog box

Query Parameters dialog box

 

By explicitly defining parameters, users are forced to type values conforming to the type. While it might not matter for text fields, it is useful for numeric and date fields. This minimizes data entry errors that cause a "Can't evaluate expression" error message to appear.

Using Access Functions

One of the most powerful features of Microsoft Access queries is their support for Access functions. This is most useful in Update queries, but can also be used in Select queries. The Advanced: Access Functions query is an example of this feature.

Figure 4. Query using a built-in VBA function

Query using a built-in VBA function

 

This query selects the Country names in descending order of name length. The second field renames itself to [Length], uses the LEN function to calculate the length of each country name, sorts the length in descending order, and excludes any records with 10 letters or fewer.

While this might not seem particularly useful, there are many situations where using Access functions is extremely useful and eliminates the need to program. The string functions in particular (Left$, Right$, Trim$, Mid$, UCase$, LCase$, and so on.) are useful for manipulating portions of strings and changing case.

Using Custom Functions

In addition to using Microsoft Access functions, queries also support user defined functions. Functions defined in VBA modules must return an appropriate value and can be used to manipulate each record. You can reference field values by passing the field name in brackets.

Here is an example where a function (StripLead) is used to remove the leading word of a phrase if it starts with "The", "An", or "A". This is useful for sorting phrases such as book titles on "real" words.

Figure 5. Query using a user-defined function

Query using a user-defined function

 

This is the code for the StripLead function. It is passed a string and returns the string without the leading word (if any).

Public Function StripLead(pstrPhrase As String) As String
  ' Comments: Get rid of leading A, An, or The in a phrase.
  ' Used for card catalog sorting.
  ' In: pstrPhrase Phrase to examine
  ' Returns: The input phrase without the "useless" first word.
  ' Returns the same phrase if the first word isn't an issue

  Dim strFirstWord As String
  Dim strReturn As String
  Dim intPos As Integer

  strReturn = pstrPhrase
  intPos = InStr(pstrPhrase, " ")
  If intPos > 0 Then
    strFirstWord = Left$(pstrPhrase, intPos - 1)
    Select Case strFirstWord
      Case "A", "An", "The"
        strReturn = Right$(pstrPhrase, Len(pstrPhrase) - intPos)
    End Select
  End If
  StripLead = strReturn
End Function


And this is the result. Notice how the sorting of the [Adjusted] field differs from the [Original] field.

Figure 6. User-defined function results

User-defined function results

Other Types of Select Queries

Top Records (number and percent)

Select queries retrieve all the records that meet your criteria. There are occasions where you only want a subset; the top or bottom number of records. Similarly, you might just want the top or bottom percent of records.

Just create a regular Select query that retrieves the records you want. By changing the Top Values query property (right-click the top portion of the query), you can specify the number of records to display. The example below (query: Other: Top 10 Auto Companies) shows only the top 10 records.

Figure 7. Querying the top values

Querying the top values

 

Notice the query is retrieving records in Descending order so the Top Values option retrieves the largest values. It simply runs the query and displays the specified number of records in the query output's order.

To display the lowest values, the query should retrieve records in Ascending order.

Top Percent of Records

Sometimes, you want a percentage of records and not a fixed number. To retrieve the top n% of the query, type a percentage (for example, 10%) instead of a value in the Top Value option.

Total Queries

Up to now, we have only retrieved records. With lots of data, it is important to calculate summaries for groups of records or totals on the entire table. This is possible by specifying Totals from the Show/Hide ribbon in Access 2007…

Figure 8. Specifying Totals from the Ribbon

Specifying Totals from the Ribbon

…or by using the View menu in Access 2003 or earlier.

Figure 9. Specifying Totals by using the View menu

Specifying Totals by using the View menu

 

This performs calculations across all the records and creates a summary result. For example, you can Sum on a numeric field to determine the total for the entire table. Additionally, you can group on fields to calculate totals for each unique combination of values across the group fields.

When Totals is selected, a new Total row appears in the query design. You can specify the type of calculation you want in that section.

Figure 10. Query with totals

Query with totals

 

For this query, the result shows average Age, Weight and Cholesterol for patients by State and Gender.

Crosstab Queries

Crosstabs are a powerful analysis tool that lets you quickly see the relationship of data between two fields. The view is a spreadsheet-like display with unique values of one field as rows, unique values of another field as columns, and the summary of another field as the cells in the matrix.

For example, with the previous example, a crosstab can clearly show the average Cholesterol between State (rows) and Sex (columns).

Figure 11. Viewing crosstab results

Viewing crosstab results

 

The easiest way to create a crosstab is to use the Crosstab Wizard. When creating a new query, select Query Wizard and then follow the Crosstab Query steps.

Figure 12. New Query Wizard

New Query Wizard

 

Crosstab queries can also be manually created by selecting Crosstab from the Query menu and specifying the Row and Column Headings.

Figure 13. Creating a crosstab query manually

Creating a crosstab query manually

Multi-table Queries

To this point, all the queries shown were for one table only. Microsoft Access queries allow very sophisticated multi-table queries. Criteria and field selections can be from any of the query's tables. Linking tables on fields is done visually by dragging a line between the fields to link.

For our previous example, we might want to show the full name of each state instead of its abbreviation. With a State table that contains the abbreviation and full names, this can be easily performed.

Figure 14. Crosstab of Patients and with State name

Crosstab of Patients and with State name

 

Notice the link on the [State] fields and the [Name] field from the States table in the query. To create multi-table queries, the Table row should be displayed. This can be activated from the View | Table Names menu. Even better, the default query options should set Show Table Names to Yes.

There are several ways to join tables in a query. The previous example was the most common which is an exact match between fields, sometimes called an inner join. Another join includes retrieving all records from one table regardless of whether there are matches in the second table. This is called a left join. If the logic is reversed (all records from the second table and matching records from the first) it is called a right join. These options can be selected by double-clicking on the linking line and choose among the three options.

Left Join Between Tables

Here is an example of a query with a left join and the results.

Figure 15. A left join query

A left join query

 

Notice how States that do not have patient data are shown with no value in the MaxOfAge and AvgOfCholesterol fields.

Figure 16. Results of a left join query

Results of a left join query

No Joins Between Tables

Queries with multiple tables do not even require a line between the tables. If no lines are specified, a record by record link is assumed. That is every record in the first table is linked to every record in the second table. This is most useful when one of the tables only has one record. Finally, tables can be linked through an expression that establishes a partial match or match based on a range of values. Examples are shown later.

Basing Queries on Other Queries

So far, the queries presented are only based on tables. However, Microsoft Access lets you also base queries on other queries. This ability to filter and analyze data across several levels is extremely powerful. The queries themselves behave identically whether the data comes from tables or queries.

Basing queries on other queries can also simplify maintenance of your database by letting you create standard queries that other queries can use. This can be particularly useful in reports. Of course, you need to be careful modifying the "core" queries.

Additionally, when you generate reports in multi-user databases, make sure that you don't use queries when you should use temporary tables that are generated by Make Table and Append queries. Queries always retrieve the most current data. If you are printing many reports while others are modifying the data, and consistency between reports is important (the numbers need to tie), you must create temporary tables with the data you need prior to printing. You can then base your queries on those "static" tables.

Percent of Total

For a field, calculating the percent of each record to the total for an entire table is useful for determining the relative size of each group. This can be achieved by creating a summary query and using that in another query with the original table. In this example, we use the Fortune100 table containing sales and profits data for 100 large corporations; and two queries (Fortune 100 Totals and Fortune 100 PercentOfTotals). Here is how they work:

Step 1: Create a Query calculating the Totals

This is a simple query that sums the values in the two fields: Sales and Profits. For clarity, the resulting fields are named TotalSales and TotalProfits.

Figure 17. Totals query with Fortune 100 data

Totals query with Fortune 100 data

 

Step 2: Create a Query with the Totals and the Original Table

This is a simple select query that retrieves fields from the Fortune100 table and creates new fields for the Percent of Total calculations. Notice the two tables are not linked with lines between them. They only interact in the Percent of Total calculations where the values in the calculated fields using TotalSales and TotalProfits as divisors.

Figure 18. Fortune 100 percent of Total Sales and Profits

Fortune 100 percent of Total Sales and Profits

 

Step 3: Run the Query

Running the query provides the desired results.

Figure 19. Results of the query

Results of the query

 

Notice how the Profit% field shows data nicely formatted (unlike Sales%). The difference is due to formatting settings on the Profit% field. While designing the query, right-click the Profit% field and notice its format is set to Percent. For the Sales% field, it's a standard number. This is the reason that the formula for Sales% includes a 100 factor that is not in the Profit% column.

Frequency Distributions

Frequency distributions reveal the number of records that contain values within numeric ranges. In this example, we want to know how many patients fall into different age categories (under 25, 25 to 40, 40 to 50, 50 to 60, and 60+). A simple two-table query calculates these results even when the size of the numeric ranges are not identical. In this example, we use two tables (Age Groups and Patients), and one query (Frequency: Age Distribution). Just follow these steps:

Step 1: Create a table defining the groups and numeric ranges

Create a table defining the groups and numeric ranges.

Create a table with four fields: Group ID (counter), Group Name (text), Minimum (number), and Maximum (number). For each record, define the groups and its low and high values.

Figure 20. Define the high and low values for each group in a Group definitions table

Define the high and low values for each group

 

Notice how the Maximum value of one record is smaller than the Minimum value of the next record. They cannot be identical or else such values would fall into two groups. In our example, the Age data are integers so using integers in this table is okay. Otherwise, you can use numbers very close to each other (for example, 24.9999999). You can name and specify as many groups as you like.

Step 2: Create multi-table Select query

Create a Totals Select query with the data table and the Group definition table defined above.

Figure 21. Query to calculate frequency distribution

Query to calculate frequency distribution

 

Notice that the two tables boxes are not linked to each other. The first two fields in the query come from the group table: the Group ID field controlling the sort order, and the Group Name description. The third field is the count of the Patient (data) table's ID field (this field is used because it is not null for every record). The final field defines the link between the two tables. Using the Patient table's Age field, the criterion is Between [Minimum] And [Maximum]. This "bins" the Patient data into the age groups defined by the Group table.

Step 3: Run the Query

Running the query provides the results

Figure 22. Frequency distribution results

Frequency distribution results

 

If the Group table's Group ID field is not used in the query, the results would be shown in Ascending order by Group Name (Under 25 would be the last record).

Action Queries

To this point, we have only covered Select queries. These queries take existing data and display it to you either record for record or in a summarized manner. Action queries actually change data. These queries can modify fields, add records to tables, delete records, and even create tables. To specify the query type, select among the options presented under the Query menu while designing a query.

Figure 23. Query Type options on the Ribbon

Query Type options on the Ribbon

 

These queries are similar to creating Select queries.

Make Table Queries

Make Table Queries are identical to Select queries except that instead of creating a datasheet display of the results, a new table is created containing the results. These are particularly useful for creating temporary tables. For example, if you are generating a series of reports while other people are changing the data, a Make Table query can create a snapshot of your data and allow your reports to work off that table. This lets you create a consistent set of reports.

Append Queries

Append Queries are also similar to Select queries, but the results are inserted as new records into another table. The field names do not need to match and expressions can also be used.

Update Queries

Update Queries allow you to modify fields. This is often used to update a field with an expression or data from another table.

Delete Queries

Delete Queries let you specify the records to be deleted from a table.

Queries in Forms, Reports, and Macros

Queries can be used in forms and reports in a variety of ways. The most common is the Record Source of the form or report. Another useful place is the RowSource of a ComboBox.

Running Queries through Macros

Running a query with a macro is very simple. Just use the OpenQuery command and specify the query name to run. If the query has parameters, the user is prompted for the values.

If you are running an Action Query, you can do the same thing; however, Action Queries usually display warning messages prior to changing data. To eliminate such messages, use the SetWarnings command to turn this off and on before and after the query.

Using and Running Queries in VBA Code

There are many ways to run queries through modules. Here are a few examples:

Creating and using a RecordSet based on a saved Select query

RecordSets let you programmatically move through a table or query. By assigning a Select query to a RecordSet, you can move through the table. Commands such as MoveNext, MoveFirst, MoveLast, MovePrevious, let you control where you are in the query. By checking the EOF status, you can make sure that you stop at the end of the table. Field values are referenced with a ! and field name (in Access 2.0, you could use "." instead of "!").


Public Sub BrowseQuery_DAO()
  ' Comments: Browse a query and display its fields in the Immediate
  ' Window using DAO

  Const cstrQueryName = "Basics: Top 10 Most Profitable Companies"
  Dim dbs As DAO.Database
  Dim rst As DAO.Recordset

  ' Open pointer to current database
  Set dbs = CurrentDb

  ' Open recordset on saved query
  Set rst = dbs.OpenRecordset(cstrQueryName)

  ' Display data from one record and move to the next record until 
  ' finished
  Do While Not rst.EOF
    Debug.Print "Company: " & rst![Company] & " Sales: " & rst![Sales] & _
      " Sales: " & rst![Profits]
    rst.MoveNext
  Loop

  rst.Close
  dbs.Close
End Sub

This example prints the company name and sales in the Immediate Window.

Assigning parameters in queries

Earlier we showed how to use parameters in queries. If you want to run a query that has parameters from within your code, you must specify the parameters in your code. Otherwise, the user is prompted for the parameter value when the query is executed.

To pass a parameter value to a query, you need to create a QueryDef and reference its parameters collection. From there you can specify each of the query's parameters. When you are finished, you can create a recordset from it (if it is a Select query) or execute it if it is an Action query. To learn more about QueryDefs and the parameters collection, refer to the online Help section under QueryDefs.


Public Sub RunParameterQuery_DAO(pstrState As String)
  ' Comments: Runs a query that contains parameters
  ' Input: pstrState   Name of state to select records

  Const cstrQueryName As String = "Basics: Parameters"
  Dim dbs As DAO.Database
  Dim qdf As DAO.QueryDef
  Dim rst As DAO.Recordset

  Set dbs = CurrentDb()
  Set qdf = dbs.QueryDefs(cstrQueryName)
  qdf.Parameters("State Abbreviation") = pstrState

  ' Open recordset on the query
  Set rst = qdf.OpenRecordset()
  Do While Not rst.EOF
    Debug.Print ("ID: " & rst![ID] & " State: " & rst![State])
    rst.MoveNext
  Loop

  rst.Close
  qdf.Close
  dbs.Close
End Sub

Using a SQL string to open a Recordset

Often it is not possible to know a query's specifications in advance. In these situations, the query needs to be programmatically created. This is done be creating a SQL string containing the query to run. The example below shows a simple case, but one can easily create a more complex example where the query string (strSQL) is based on other situations (field values, user selections, and so on.).


Public Sub RecordsetFromSQL_DAO()
  ' Comments: Browse the results of a SQL string and display it in the 
  ' Immediate Window

  Dim dbs As DAO.Database
  Dim rst As DAO.Recordset
  Dim strSQL As String

  strSQL = "SELECT Left([Company],1) AS Letter, " & _
    "Count(Company) AS [Count], " & _
    "Avg(Sales) AS AvgOfSales, Avg(Profits) AS AvgOfProfits " & _
    "FROM Fortune100 " & _
    "GROUP BY Left([Company],1)"

  ' Open pointer to current database
  Set dbs = CurrentDb()

  ' Create recordset based on SQL
  Set rst = dbs.OpenRecordset(strSQL)

  Do While Not rst.EOF
    Debug.Print "Company Letter: " & rst![Letter] & " & _
    " Sales: " & rst![AvgOfSales] & " & _
    "Profits: " & rst![AvgOfProfits]
    rst.MoveNext
  Loop

  rst.Close
  dbs.Close

End Sub


Running your own query string is identical to the previous examples. Just base a RecordSet on the query string.

Running a stored Action query

To run a saved Action query, use the query Execute command. The simple procedure below lets you easily run a saved query. Just pass the name of the query and it is performed.


Public Sub RunActionQuery_DAO(pstrQueryName As String)
  ' Comments: Sample code of running a stored (action) query
  ' Input: pstrQueryName   Name of saved query to run

  DoCmd.SetWarnings False
  CurrentDb.Execute pstrQueryName
  DoCmd.SetWarnings True

End Sub

This procedure sets up a database variable referencing the current database, and creates a QueryDef based on the query name. The Warning message is temporarily turned off before executing the query and reset afterwards. DoEvents and DBEngine.Idle commands are used to make sure that the Jet Engine has completed its tasks and releases its locks.

Creating a table with a Make Table Query SQL string

A Make Table query is an Action query and can be run with the Action Query example shown earlier. The only wrinkle here is to make sure that the new table is deleted prior to the Make Table query's execution. Also, the example below shows another way to execute a query without using a QueryDef.


Public Sub MakeTableFromSQL_DAO()
  ' Comments: Sample code running an action query created in a SQL string
  ' Includes simple error trapping to handle problems creating 
  ' table

  Const cstrNewTableName As String = "Fortune100 LetterSummary"
  Dim strSQL As String
  Dim strError As String

  ' SQL string to create a new table
  strSQL = "SELECT Left([Company],1) AS Letter, " & _
    "Count(Company) AS [Count], " & _
    "Avg(Sales) AS AvgOfSales, Avg(Profits) AS AvgOfProfits " & _
    "INTO [" & cstrNewTableName & "] " & _
    "FROM Fortune100 " & _
    "GROUP BY Left([Company],1)"

  ' Delete table if it exists
  On Error Resume Next
  DoCmd.DeleteObject acTable, cstrNewTableName

  Err.Clear

  ' Execute (run) the query
  CurrentDb.Execute strSQL
  If Err.Number <> 0 Then
    strError = Err.Description
  End If

  On Error GoTo 0

  If strError = "" Then
    MsgBox "Table: [" & cstrNewTableName & "] created"
    DoCmd.OpenTable cstrNewTableName
  Else
    MsgBox "Error creating table: " & strError
  End If

End Sub

Additional code is provided in the sample database with this article.

Additional Resources from Microsoft

For more information about Access 2007, see the following resources:

About the Author

Luke Chung founded FMS in 1986 to provide custom database solutions. He has directed the company’s product development and consulting services efforts as the database industry evolved. In addition to being a primary author and designer of many FMS commercial products, Luke has personally provided consulting services to a wide range of clients. A recognized database expert and highly regarded authority in the Microsoft Access developer community, Luke was featured by Microsoft as an Access Hero during the Access 10-year anniversary celebration. Luke is a popular speaker at conferences in the US and Europe, and has published many articles in industry magazines. He is a past president of the Washington, DC chapter of the Entrepreneurs Organization (EO Network), serves on the Fairfax County School Superintendent's Community Advisory Council, and is a graduate of Harvard University with Bachelor and Master Degrees in Engineering and Applied Sciences.

Additional Resources from FMS, Inc.

FMS offers a variety of other resources to help you maximize the value of your Microsoft Access data.

Document and Improve Queries with Total Access Analyzer

Total Access Analyzer documents your entire database to provide detailed information on each object, where it's used, and recommendations to fix or improve them. Part of the analysis includes Queries. Here are some examples of the results:

Advanced Numerical Analysis with Total Access Statistics

If you want to extend the power of Access queries with more advanced numerical analysis, learn more about the Total Access Statistics program from FMS. It is the leading Microsoft Access statistical analysis program. It analyzes your Access table, linked table, or query in an MDB, ACCDB or ADP, and puts its results in tables. Generate percentiles, frequency distributions, regressions, correlations, rankings, data normalization, advanced crosstabs, t-Tests, ANOVA, non-parametrics, probabilities, and so on. Interactive Wizard and VBA programmatic interfaces are included with a runtime distribution library. Adding advanced numerical analysis couldn't be easier! Get more information including a free trial version.

Recordset Builder in Total Visual CodeTools

If you want to simplify the creation and maintenance of Access/VBA code, learn about the Total Visual CodeTools program from FMS. It helps VB6/VBA developers create new code, clean up existing code, and deliver more robust solutions. Two of its builders related to queries are:

  • The Recordset Builder lets you point to a database, select a table or query/view, select all or some of the fields, and automatically generate code to browse, edit, or add records to it. Choose whether you want it to use ADO or DAO, and whether you reference the current database or an external one.

  • The Long Text/SQL Builder converts SQL from a query into a quoted string that you can add to your VBA Modules, while handling quotes and smart line continuations so parts like FROM, GROUP BY, WHERE, and so on start new lines.

Get more information including a free 30 day trial version.

Database Maintenance and Macro Scheduler

As you add more data to your database, make sure that you compact it regularly for optimal results and that you make backups. Additionally, check for any tasks that need to run repeatedly, such as a particular set of queries, data downloads, exports, or batch of reports that you must print. You can automate these with a macro or some code. To launch this on a regular schedule, use Total Visual Agent from FMS. Total Visual Agent is a Microsoft Access scheduler to run macros, compact, and other database chores on an hourly, daily, weekly, monthly, or one time event. Easily manage an unlimited number of databases across your network. Get more information including a free trial version.

Other Technical Papers and Tips

Here are some other FMS papers related to data that you might find helpful:

Microsoft Access Consulting Services from FMS

FMS also offers custom software development services. If you're in over your head or just don't have time, contact the FMS team. We can help you maintain, enhance, and/or migrate your Microsoft Access applications. Here's more on the FMS Microsoft Access Consulting Services.

Community Additions

ADD
Show:
© 2014 Microsoft. All rights reserved.