CASE statement

Selects an execution path based on multiple cases.

Syntax 1

CASE value-expression
WHEN [ constant | NULL ] THEN statement-list ...
[ WHEN [ constant | NULL ] THEN statement-list ] ...
[ ELSE statement-list ]
END [ CASE ]

Syntax 2

CASE
WHEN [ search-condition | NULL] THEN statement-list ...
[ WHEN [ search-condition | NULL] THEN statement-list ] ...
[ ELSE statement-list ]
END [ CASE ]

Remarks

Syntax 1 The CASE statement is a control statement that allows you to choose a list of SQL statements to execute based on the value of an expression. The value-expression is an expression that takes on a single value, which may be a string, a number, a date, or other SQL data type. If a WHEN clause exists for the value of value-expression, the statement-list in the WHEN clause is executed. If no appropriate WHEN clause exists, and an ELSE clause exists, the statement-list in the ELSE clause is executed. Execution resumes at the first statement after the END CASE.
If the value-expression can be null, use the ISNULL function to replace the NULL value-expression with a different expression.

Syntax 2 With this form, the statements are executed for the first satisfied search-condition in the CASE statement. The ELSE clause is executed if none of the search-conditions are met.

If the expression can be NULL, use the following syntax for the first search-condition:

WHEN search-condition IS NULL THEN statement-list

Note

Do not confuse the syntax of the CASE statement with that of the CASE expression.

Permissions

Side effects

Standards and compatibility

SQL/2008 The CASE statement is part of language feature P002 (Computational completeness) of the SQL/2008 standard. The use of END alone, rather than END CASE, is a vendor extension.
Transact-SQL The CASE statement is supported by Adaptive Server Enterprise.

Example

The following procedure using a case statement classifies the products listed in the Products table of the SQL Anywhere sample database into one of shirt, hat, shorts, or unknown.

CREATE PROCEDURE ProductType (IN product_ID INT, OUT type CHAR(10))
BEGIN
   DECLARE prod_name CHAR(20);
   SELECT Name INTO prod_name FROM Products
   WHERE ID = product_ID;
   CASE prod_name
   WHEN 'Tee Shirt' THEN
      SET type = 'Shirt'
   WHEN 'Sweatshirt' THEN
      SET type = 'Shirt'
   WHEN 'Baseball Cap' THEN
      SET type = 'Hat'
   WHEN 'Visor' THEN
      SET type = 'Hat'
   WHEN 'Shorts' THEN
      SET type = 'Shorts'
   ELSE
      SET type = 'UNKNOWN'
   END CASE;
END;

The following example uses Syntax 2 to generate a message about product quantity within the SQL Anywhere sample database.

CREATE PROCEDURE StockLevel (IN product_ID INT)
BEGIN
   DECLARE qty INT;
   SELECT Quantity INTO qty FROM Products
   WHERE ID = product_ID;
   CASE
   WHEN qty < 30 THEN
      MESSAGE 'Order Stock' TO CLIENT;
   WHEN qty > 100 THEN
      MESSAGE 'Overstocked' TO CLIENT;
   ELSE
      MESSAGE 'Sufficient stock on hand' TO CLIENT;
   END CASE;
END;

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