Cursors

Cursors are supported inside stored procedures and functions and triggers. The syntax is as in embedded SQL. Cursors are currently asensitive, read-only, and non-scrolling. Asensitive means that the server may or may not make a copy of its result table.
Cursors must be declared before declaring handlers, and variables and conditions must be declared before declaring either cursors or handlers.
Example:

CREATE PROCEDURE curdemo()

BEGIN

  DECLARE done INT DEFAULT 0;

  DECLARE a CHAR(16);

  DECLARE b,c INT;

  DECLARE cur1 CURSOR FOR SELECT id,data FROM test.t1;

  DECLARE cur2 CURSOR FOR SELECT i FROM test.t2;

  DECLARE CONTINUE HANDLER FOR SQLSTATE '02000' SET done = 1;

 

  OPEN cur1;

  OPEN cur2;

 

  REPEAT

    FETCH cur1 INTO a, b;

    FETCH cur2 INTO c;

    IF NOT done THEN

       IF b < c THEN

          INSERT INTO test.t3 VALUES (a,b);

       ELSE

          INSERT INTO test.t3 VALUES (a,c);

       END IF;

    END IF;

  UNTIL done END REPEAT;

 

  CLOSE cur1;

  CLOSE cur2;

END

Declaring Cursors

DECLARE cursor_name CURSOR FOR select_statement

This statement declares a cursor. Multiple cursors may be declared in a routine, but each cursor in a given block must have a unique name.
The SELECT statement cannot have an INTO clause.

Cursor OPEN Statement

OPEN cursor_name

This statement opens a previously declared cursor.

Cursor FETCH Statement

FETCH cursor_name INTO var_name [, var_name] ...

This statement fetches the next row (if a row exists) using the specified open cursor, and advances the cursor pointer.

Cursor CLOSE Statement

CLOSE cursor_name

This statement closes a previously opened cursor.