Mysql随笔

TRUNCATE TABLE 表名

有外键约束时

SET FOREIGN_KEY_CHECKS=0;
TRUNCATE TABLE 表名
SET FOREIGN_KEY_CHECKS=1;

DELETE FROM   表名

group by [去重复字段表1，.....]

FROM `p_user_service` WHERE user_id=25 //返回天
SELECT TIMESTAMPDIFF(SECOND, `start_time`, NOW()) FROM `p_user_service` WHERE user_id=25 //返回秒差
SELECT TIMESTAMPDIFF(MINUTE, `start_time`, NOW()) FROM `p_user_service` WHERE user_id=25 //返回分钟差
SELECT TIMESTAMPDIFF(HOUR, `start_time`, NOW()) FROM `p_user_service` WHERE user_id=25 //返回时差
SELECT TIMESTAMPDIFF(DAY, `start_time`, NOW()) FROM `p_user_service` WHERE user_id=25 //返回天数差

max_allowed_packet=300M
wait_timeout=200000
interactive_timeout = 200000

CONCAT_WS(
'****',
SUBSTRING(m.member_phone, 1, 4),
SUBSTRING(m.member_phone, 9, 3)
) AS memberPhone,