mysql

show Variables like '%table_names'
show full columns from table_name
show table status

default-character-set=utf8
lower_case_table_names=2

SHOW GLOBAL VARIABLES LIKE 'group_concat_max_len';
SET GLOBAL group_concat_max_len=1048576;

SET @i=0;
SELECT
Id,
(@i:=@i+1) sn
FROM Microcampus_T_Activity
LIMIT 1,50

SET GLOBAL max_allowed_packet=524288000

SELECT CONCAT('KILL ',id,';')  AS command
FROM information_schema.processlist
WHERE TIME>3600 AND `user`='root'

SHOW ENGINE INNODB STATUS;

ALTER TABLE tab01 AUTO_INCREMENT=10020030;

INSERT INTO tab01 () VALUES();
SELECT @@IDENTITY;

/* 删除语句的真义 */
DELETE tu FROM ThirdUser tu, MyThirdUser t
WHERE tu.OpenId=t.OpenId;

SET GLOBAL slow_query_log=ON;
SET GLOBAL slow_launch_time=5;
SHOW VARIABLES LIKE "%slow%";