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Create Subqueries (Visual Database Tools)

 

You can use the results of one query as the input for another. You can use the results of a subquery as a statement that uses the IN( ) function, the EXISTS operator, or the FROM clause.

You can create a subquery by entering it directly into the SQL pane or by copying a query and pasting it into another.

To define a subquery in the SQL pane

  1. Create the primary query.

  2. In the SQL pane, select the SQL statement, and then use Copy to move the query to the Clipboard.

  3. Start the new query, and then use Paste to move the first query into the new query's WHERE or FROM clause.

    For example, imagine you have two tables, products and suppliers, and you want to create a query showing all products for suppliers in Sweden. Create the first query on the suppliers table to find all Swedish suppliers:

    SELECT supplier_id
    FROM supplier
    WHERE (country = 'Sweden')
    

    Use the Copy command to move this query to the Clipboard. Create the second query using the products table, listing the information you need about products:

    SELECT product_id, supplier_id, product_name
    FROM products
    

    In the SQL pane, add a WHERE clause to the second query, then paste the first query from the Clipboard. Place parentheses around the first query, so that the end result looks like this:

    SELECT product_id, supplier_id, product_name
    FROM products
    WHERE supplier_id IN
       (SELECT supplier_id
      FROM supplier
      WHERE (country = 'Sweden'))
    
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