TIMESTAMP 类型字段与 CHAR 比较:

BEGIN

#Routine body goes here...

DECLARE rdToday CHAR(10) DEFAULT CURDATE();

DECLARE rdBegin CHAR(19) DEFAULT CONCAT(rdToday, '00:00:00');

DECLARE rdEnd CHAR(19) DEFAULT CONCAT(rdToday, '23:59:59');

SELECT mdc_ordertime FROM mz_drugrecipe WHERE mdc_ordertime BETWEEN rdBegin AND rdEnd;

END

TIMESTAMP 类型字段与 TIMESTAMP 比较:

BEGIN

#Routine body goes here...

DECLARE rdBegin TIMESTAMP DEFAULT CURDATE();

DECLARE rdEnd TIMESTAMP DEFAULT TIMESTAMPADD(SECOND, -1, DATE_ADD(CURDATE(),INTERVAL 1 DAY));

-- 或:

-- DECLARE rdToday CHAR(10) DEFAULT CURDATE();

-- DECLARE rdBegin CHAR(19) DEFAULT CONCAT(rdToday, '00:00:00');

-- DECLARE rdEnd CHAR(19) DEFAULT CONCAT(rdToday, '23:59:59');

SELECT mdc_ordertime FROM mz_drugrecipe WHERE mdc_ordertime BETWEEN rdBegin AND rdEnd;

END

实验步骤:

都执行 100000 次,第一种 CHAR 变量与 TIMESTAMP 类型字段比较,花费时间40s+, 第二种 TIMESTAMP(不论通过哪种构造方式构造)变量与 TIMESTAMP 类型字段比较,花费时间 30s+.

结论:

应该将要比较的变量化为目标字段的类型 TIMESTAMP 后再进行比较.