MYSQL PL/SQL
一组SQL语句集，速度快，只有首次执行需经过编译和优化步骤，后续被调用可以直接执行
Sample:
DROP PROCEDURE IF EXISTS `proc_adder`;
DELIMITER &&
CREATE DEFINER=`root`@`localhost` PROCEDURE `proc_adder`(IN a int, IN b int, OUT sum int)
BEGIN
DECLARE c int;
/*DECLARE c int DEFAULT 10*/
if a is null then set a = 0;
end if;
if b is null then set b = 0;
end if;
set sum = a + b;
END
&&
DELIMITER ;
说明：
DEFINER: 创建者
DECLARE: 定义变量
SET:为变量赋
SELECT…INTO语句为变量赋值如下：
SELECT col_name[,…] INTO var_name[,…]
FROM table_name WEHRE condition
DELIMITER：
MySQL中默认的语句结束符为分号（;）。存储过程中的SQL语句需要分号（;）来结束。为了避免冲突，首先用"DELIMITER &&"将MySQL的结束符设置为&&。最后再用"DELIMITER ;"来将结束符恢复成分号。这与创建触发器时是一样的。
常用语法：
IF:
IF type = 0 THEN
set c = 'param is 0';
ELSEIF type = 1 THEN
set c = 'param is 1';
ELSE
set c = 'param is others, not 0 or 1';
END IF;
CASE:
CASE type
WHEN 0 THEN
set c = 'param is 0';
WHEN 1 THEN
set c = 'param is 1';
ELSE
set c = 'param is others, not 0 or 1';
END CASE;
WHILE:
DECLARE i int;
DECLARE s int;
SET i = 0;
SET s = 0;
WHILE i <= n DO
set s = s + i;
set i = i + 1;
END WHILE;
