Mysql 之 条件判断、循环语句
官方英文文档：
http://dev.mysql.com/doc/refman/5.0/en/flow-control-statements.html

************************** IF **************************
语法：

IF search_condition THEN statement_list    [ELSEIF search_condition THEN statement_list] ...    [ELSE statement_list]END IF

实例：

DELIMITER$$DROP PROCEDURE IF EXISTS pro_if$$CREATE PROCEDURE pro_if(i INT)BEGINIF i < 60 THENSELECT '需继续努力，争取过线！' AS result;ELSEIF i < 85 THENSELECT '再努力点，争取达优！' AS result;ELSE SELECT '不错哦，恭喜，恭喜！' AS result;END IF;END$$

************************** CASE **************************
语法：

CASE case_value    WHEN when_value THEN statement_list    [WHEN when_value THEN statement_list] ...    [ELSE statement_list]END CASE

Or:

CASE    WHEN search_condition THEN statement_list    [WHEN search_condition THEN statement_list] ...    [ELSE statement_list]END CASE

实例：

DELIMITER$$DROP PROCEDURE IF EXISTS pro_case$$CREATE PROCEDURE pro_case(i INT)BEGINCASE iWHEN 1 THEN SELECT 'you male!' AS result;WHEN 0 THEN SELECT 'you female!' AS result;ELSESELECT 'third sex!' AS result;END CASE;END$$