SELECT (Transact-SQL)

SELECT (Transact-SQL)

 

THIS TOPIC APPLIES TO:yesSQL Server (starting with 2008) yesAzure SQL Database yesAzure SQL Data Warehouse yesParallel Data Warehouse

Retrieves rows from the database and enables the selection of one or many rows or columns from one or many tables in SQL Server. The full syntax of the SELECT statement is complex, but the main clauses can be summarized as:

[ WITH { [ XMLNAMESPACES ,] [ <common_table_expression> ] } ]

SELECT select_list [ INTO new_table ]

[ FROM table_source ] [ WHERE search_condition ]

[ GROUP BY group_by_expression ]

[ HAVING search_condition ]

[ ORDER BY order_expression [ ASC | DESC ] ]

The UNION, EXCEPT and INTERSECT operators can be used between queries to combine or compare their results into one result set.

Topic link icon Transact-SQL Syntax Conventions


<SELECT statement> ::=  
    [ WITH { [ XMLNAMESPACES ,] [ <common_table_expression> [,...n] ] } ]
    <query_expression> 
    [ ORDER BY { order_by_expression | column_position [ ASC | DESC ] } 
  [ ,...n ] ] 
    [ <FOR Clause>] 
    [ OPTION ( <query_hint> [ ,...n ] ) ] 
<query_expression> ::= 
    { <query_specification> | ( <query_expression> ) } 
    [  { UNION [ ALL ] | EXCEPT | INTERSECT }
        <query_specification> | ( <query_expression> ) [...n ] ] 
<query_specification> ::= 
SELECT [ ALL | DISTINCT ] 
    [TOP ( expression ) [PERCENT] [ WITH TIES ] ] 
    < select_list > 
    [ INTO new_table ] 
    [ FROM { <table_source> } [ ,...n ] ] 
    [ WHERE <search_condition> ] 
    [ <GROUP BY> ] 
    [ HAVING < search_condition > ] 
-- Azure SQL Data Warehouse and Parallel Data Warehouse
[ WITH <common_table_expression> [ ,...n ] ]
SELECT <select_criteria>
[;]

<select_criteria> ::=
    [ TOP ( top_expression ) ] 
    [ ALL | DISTINCT ] 
    { * | column_name | expression } [ ,...n ] 
    [ FROM { table_source } [ ,...n ] ]
    [ WHERE <search_condition> ] 
    [ GROUP BY <group_by_clause> ] 
    [ HAVING <search_condition> ] 
    [ ORDER BY <order_by_expression> ]
    [ OPTION ( <query_option> [ ,...n ] ) ]

Because of the complexity of the SELECT statement, detailed syntax elements and arguments are shown by clause:

WITH XMLNAMESPACES

WITH common_table_expression

HAVING

SELECT Clause

UNION

INTO Clause

EXCEPT and INTERSECT

FROM

ORDER BY

WHERE

FOR Clause

GROUP BY

OPTION Clause

The order of the clauses in the SELECT statement is significant. Any one of the optional clauses can be omitted, but when the optional clauses are used, they must appear in the appropriate order.

SELECT statements are permitted in user-defined functions only if the select lists of these statements contain expressions that assign values to variables that are local to the functions.

A four-part name constructed with the OPENDATASOURCE function as the server-name part can be used as a table source wherever a table name can appear in a SELECT statement. A four-part name cannot be specified for Azure SQL Database.

Some syntax restrictions apply to SELECT statements that involve remote tables.

The following steps show the logical processing order, or binding order, for a SELECT statement. This order determines when the objects defined in one step are made available to the clauses in subsequent steps. For example, if the query processor can bind to (access) the tables or views defined in the FROM clause, these objects and their columns are made available to all subsequent steps. Conversely, because the SELECT clause is step 8, any column aliases or derived columns defined in that clause cannot be referenced by preceding clauses. However, they can be referenced by subsequent clauses such as the ORDER BY clause. Note that the actual physical execution of the statement is determined by the query processor and the order may vary from this list.

  1. FROM

  2. ON

  3. JOIN

  4. WHERE

  5. GROUP BY

  6. WITH CUBE or WITH ROLLUP

  7. HAVING

  8. SELECT

  9. DISTINCT

  10. ORDER BY

  11. TOP

Selecting data requires SELECT permission on the table or view, which could be inherited from a higher scope such as SELECT permission on the schema or CONTROL permission on the table. Or requires membership in the db_datareader or db_owner fixed database roles, or the sysadmin fixed server role. Creating a new table using SELECT INTO also requires both the CREATE TABLE permission, and the ALTER SCHEMA permission on the schema that owns the new table.

This section shows three code examples. This first code example returns all rows (no WHERE clause is specified) and all columns (using the *) from the DimEmployee table in the AdventureWorksPDW2012 database.

-- Uses AdventureWorks

SELECT *
FROM DimEmployee
ORDER BY LastName;

This next example using table aliasing to achieve the same result.

-- Uses AdventureWorks

SELECT e.*
FROM DimEmployee AS e
ORDER BY LastName;

This example returns all rows (no WHERE clause is specified) and a subset of the columns (FirstName, LastName, StartDate) from the DimEmployee table in the AdventureWorksPDW2012 database. The third column heading is renamed to FirstDay.

-- Uses AdventureWorks

SELECT FirstName, LastName, StartDate AS FirstDay
FROM DimEmployee 
ORDER BY LastName;

This example returns only the rows for DimEmployee that have an EndDate that is not NULL and a MaritalStatus of ‘M’ (married).

-- Uses AdventureWorks

SELECT FirstName, LastName, StartDate AS FirstDay
FROM DimEmployee 
WHERE EndDate IS NOT NULL 
AND MaritalStatus = 'M'
ORDER BY LastName;

The following example returns all rows from the DimEmployee table, and calculates the gross pay for each employee based on their BaseRate and a 40 hour work week.

-- Uses AdventureWorks

SELECT FirstName, LastName, BaseRate, BaseRate * 40 AS GrossPay
FROM DimEmployee
ORDER BY LastName;

The following example uses DISTINCT to generate a list of all unique titles in the DimEmployee table.

-- Uses AdventureWorks

SELECT DISTINCT Title
FROM DimEmployee
ORDER BY Title;

The following example finds the total amount for all sales on each day.

-- Uses AdventureWorks

SELECT OrderDateKey, SUM(SalesAmount) AS TotalSales
FROM FactInternetSales
GROUP BY OrderDateKey
ORDER BY OrderDateKey;

Because of the GROUP BY clause, only one row containing the sum of all sales is returned for each day.

The following example finds the average price and the sum of Internet sales for each day, grouped by order date and the promotion key.

-- Uses AdventureWorks

SELECT OrderDateKey, PromotionKey, AVG(SalesAmount) AS AvgSales, SUM(SalesAmount) AS TotalSales
FROM FactInternetSales
GROUP BY OrderDateKey, PromotionKey
ORDER BY OrderDateKey; 

The following example puts the results into groups after retrieving only the rows with order dates later than August 1, 2002.

-- Uses AdventureWorks

SELECT OrderDateKey, SUM(SalesAmount) AS TotalSales
FROM FactInternetSales
WHERE OrderDateKey > '20020801'
GROUP BY OrderDateKey
ORDER BY OrderDateKey;

The following example groups by an expression. You can group by an expression if the expression does not include aggregate functions.

-- Uses AdventureWorks

SELECT SUM(SalesAmount) AS TotalSales
FROM FactInternetSales
GROUP BY (OrderDateKey * 10);

The following example finds the sum of sales per day, and orders by the day.

-- Uses AdventureWorks

SELECT OrderDateKey, SUM(SalesAmount) AS TotalSales
FROM FactInternetSales
GROUP BY OrderDateKey
ORDER BY OrderDateKey;

This query uses the HAVING clause to restrict results.

-- Uses AdventureWorks

SELECT OrderDateKey, SUM(SalesAmount) AS TotalSales
FROM FactInternetSales
GROUP BY OrderDateKey
HAVING OrderDateKey > 20010000
ORDER BY OrderDateKey;

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