CREATE PROCEDURE statement

Description

Examples

Example 1

This procedure uses a case statement to classify the results of a query.

CREATE PROCEDURE ProductType (IN product_id INT, OUT type CHAR(10))
BEGIN
  DECLARE prod_name CHAR(20) ;
  SELECT name INTO prod_name FROM "GROUPO"."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

Example 2

This procedure uses a cursor and loops over the rows of the cursor to return a single value.

CREATE PROCEDURE TopCustomer (OUT TopCompany CHAR(35), OUT TopValue INT)
BEGIN
  DECLARE err_notfound EXCEPTION
 	FOR SQLSTATE '02000' ;
  DECLARE curThisCust CURSOR FOR
  SELECT CompanyName, CAST( 	  sum(SalesOrderItems.Quantity *
  Products.UnitPrice) AS INTEGER) VALUE
  FROM Customers
  LEFT OUTER JOIN SalesOrders
  LEFT OUTER JOIN SalesorderItems
  LEFT OUTER JOIN Products
  GROUP BY CompanyName ;


  DECLARE ThisValue INT ;
  DECLARE ThisCompany CHAR(35) ;
  SET TopValue = 0 ;
  OPEN curThisCust ;
  CustomerLoop:
  LOOP
    FETCH NEXT curThisCust
    INTO ThisCompany, ThisValue ;
    IF SQLSTATE = err_notfound THEN
      LEAVE CustomerLoop ;
    END IF ;
    IF ThisValue > TopValue THEN
      SET TopValue = ThisValue ;
      SET TopCompany = ThisCompany ;
      END IF ;
  END LOOP CustomerLoop ;
  CLOSE curThisCust ;
END

Usage

CREATE PROCEDURE creates a procedure in the database. Users with DBA authority can create procedures for other users by specifying an owner. A procedure is invoked with a CALL statement.

When procedures are executed using CALL, not all parameters need to be specified. If a default value is provided in the CREATE PROCEDURE statement, missing parameters are assigned the default values. If an argument is not provided in the CALL statement, and no default is set, an error is given.

SQLSTATE and SQLCODE are special parameters that output the SQLSTATE or SQLCODE value when the procedure ends (they are OUT parameters). Whether or not a SQLSTATE and SQLCODE parameter is specified, the SQLSTATE and SQLCODE special values can always be checked immediately after a procedure call to test the return status of the procedure.

The SQLSTATE and SQLCODE special values are modified by the next SQL statement. Providing SQLSTATE or SQLCODE as procedure arguments allows the return code to be stored in a variable.

Specifying CREATE OR REPLACE PROCEDURE creates a new procedure, or replaces an existing procedure with the same name. This clause changes the definition of the procedure, but preserves existing permissions. You cannot use the OR REPLACE clause with temporary procedures. Also, an error is returned if the procedure being replaced is already in use.

Specifying CREATE TEMPORARY PROCEDURE means that the stored procedure is visible only by the connection that created it, and that it is automatically dropped when the connection is dropped. You can also explicitly drop temporary stored procedures. You cannot perform ALTER, GRANT, or REVOKE on them, and, unlike other stored procedures, temporary stored procedures are not recorded in the catalog or transaction log.

Temporary procedures execute with the permissions of their creator (current user), or specified owner. You can specify an owner for a temporary procedure when:

• The temporary procedure is created within a permanent stored procedure

• The temporary and permanent procedure both have the same owner

To drop the owner of a temporary procedure, drop the temporary procedure first.

You can create and drop temporary stored procedures when you are connected to a read-only database; they cannot be external procedures.

For example, the following temporary procedure drops the table called CustRank, if it exists. For this example, the procedure assumes that the table name is unique and can be referenced by the procedure creator without specifying the table owner:

CREATE TEMPORARY PROCEDURE drop_table( IN @TableName char(128) )
BEGIN
	IF EXISTS  ( SELECT * FROM SYS.SYSTAB WHERE
	table_name = @TableName ) 
	THEN EXECUTE IMMEDIATE 
	'DROP TABLE "' || @TableName || '"';
	MESSAGE 'Table "' || @TableName || 
	'" dropped' to client;
	END IF;
END;
CALL drop_table( 'CustRank' )

If your procedure returns only one result set, use a RESULT clause. The presence of this clause prevents ODBC and Open Client applications from describing the result set again after a cursor is open.

To handle multiple result sets, ODBC must describe the currently executing cursor, not the procedure’s defined result set. Therefore, ODBC does not always describe column names as defined in the RESULT clause of the procedure definition. To avoid this problem, use column aliases in the SELECT statement that generates the result set.

Extra memory is used when you specify SQL SECURITY INVOKER, because annotation must be done for each user that calls the procedure. Also, name resolution is performed as the invoker as well. Therefore, qualify all object names (tables, procedures, and so on) with their appropriate owner. For example, suppose user1 creates this procedure:

 CREATE PROCEDURE user1.myProcedure()
	RESULT( columnA INT )
	SQL SECURITY INVOKER
	BEGIN
		SELECT columnA FROM table1;
	END;

If user2 attempts to run this procedure and a table user2.table1 does not exist, a table lookup error results. Additionally, if a user2.table1 does exist, that table is used instead of the intended user1.table1. To prevent this situation, qualify the table reference in the statement (user1.table1, instead of just table1).

If you use ON EXCEPTION RESUME, the procedure takes an action that depends on the setting of the ON_TSQL_ERROR option. If ON_TSQL_ERROR is set to CONDITIONAL (which is the default) the execution continues if the next statement handles the error; otherwise, it exits.

Error-handling statements include:

• IF

• SELECT @variable =

• CASE

• LOOP

• LEAVE

• CONTINUE

• CALL

• EXECUTE

• SIGNAL

• RESIGNAL

• DECLARE

• SET VARIABLE

Do not use explicit error-handling code with an ON EXCEPTION RESUME clause.

Remote procedures can return only up to 254 characters in output variables.

If a remote procedure can return a result set, even if it does not return one in all cases, then the local procedure definition must contain a RESULT clause.

Automatic commit.

Standards

Permissions

Must have RESOURCE authority, unless creating a temporary procedure. For external procedures or to create a procedure for another user, must have DBA authority.

See also