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SQL Anywhere 11.0.1 (Français) » SQL Anywhere Server - SQL Usage » Querying and Modifying Data » Using subqueries » Testing subqueries

 

Subqueries and the ANY test

The ANY test, used in conjunction with one of the SQL comparison operators (=, >, <, >=, <=, !=, <>, !>, !<), compares a single value to the column of data values produced by the subquery. To perform the test, SQL uses the specified comparison operator to compare the test value to each data value in the column. If any of the comparisons yields a TRUE result, the ANY test returns TRUE.

A subquery used with ANY must return a single column.

Example

Find the order and customer IDs of those orders placed after the first product of the order #2005 was shipped.

SELECT ID, CustomerID
FROM SalesOrders
WHERE OrderDate > ANY (
   SELECT ShipDate
   FROM SalesOrderItems
   WHERE ID=2005 );
ID CustomerID
2006 105
2007 106
2008 107
2009 108
... ...

In executing this query, the main query tests the order dates for each order against the shipping dates of every product of the order #2005. If an order date is greater than the shipping date for one shipment of order #2005, then that ID and customer ID from the SalesOrders table are part of the result set. The ANY test is analogous to the OR operator: the above query can be read, "Was this sales order placed after the first product of the order #2005 was shipped, or after the second product of order #2005 was shipped, or..."

Understanding the ANY operator

The ANY operator can be a bit confusing. It is tempting to read the query as "Return those orders placed after any products of order #2005 were shipped." But this means the query will return the order IDs and customer IDs for the orders placed after all products of order #2005 were shipped—which is not what the query does.

Instead, try reading the query like this: "Return the order and customer IDs for those orders placed after at least one product of order #2005 was shipped." Using the keyword SOME may provide a more intuitive way to phrase the query. The following query is equivalent to the previous query.

SELECT ID, CustomerID
FROM SalesOrders
WHERE OrderDate > SOME (
   SELECT ShipDate
   FROM SalesOrderItems
   WHERE ID=2005 );

The keyword SOME is equivalent to the keyword ANY.

Notes about the ANY operator

There are two additional important characteristics of the ANY test:

  • Empty subquery result set   If the subquery produces an empty result set, the ANY test returns FALSE. This makes sense, since if there are no results, then it is not true that at least one result satisfies the comparison test.

  • NULL values in subquery result set   Assume that there is at least one NULL value in the subquery result set. If the comparison test is FALSE for all non-NULL data values in the result set, the ANY search returns UNKNOWN. This is because in this situation, you cannot conclusively state whether there is a value for the subquery for which the comparison test holds. There may or may not be a value, depending on the correct values for the NULL data in the result set. For more information about the ANY search condition, see ANY and SOME search conditions.