show create table mytable; show index from mytable; show culumn from mytable; show privileges; show variables; show global variables; show session variables; select current_user; UCASE,CONCAT(str,'',name),left(str,1),MOD(30,8) SQRT(30),ROUND(3,0)COALESCE(str,1),YEAR(date),DAYNAME(date),MONTHNAME(date),DAYOFYEAR(date) DATEDIFF(startDate,endDate),SUBSTRING(str,1),ASCIIL(str),LENGTH(str), LTRIM(RTRIM('SQL')), REPLACE(str,org,rep) cast 类型转换表达式 cast('123' as signed integer) case(121214 as time) conv(6,10,2)进制转换 bin(32)二进制表示 interval 10 day 10天间隔 interval 100 week interval 20 month interval 5 year addtime(orgDate,intervalTime) 行表达式: select * from mytabl where (name,age)=('weijian',34) select * from mytabl where name<=>null; 关联性子查询: escape select * from mytable where name like '%#_%' escape '#'; 查找name中包含下划线的记录,在like中忽略escape后面的字符转义 select * from mytale where name regexp 'e'; create fulltext index index_name on mytable(name) select * from mytable where match(name) against('abc') 查找mane中包含abc的记录 select * from mytable where not exist(select 'nothin' from mytable2 where name = mytable.name) select * from mytable where birthdate <= all(select birthdate from mytable) select * from mytable where birthdate > any(select birthdate from mytable) select count(distinct substr(name,1,1)) from mytable; select count(distinct substr(name,1,1)),count(distinct age)) from mytable; select sum(acount) from mytabl group by acount having sum(acount) >= (select sum(acount) from mytable group by acount) select name,age from mytable order by 2; 根据select 的第二个表达式来排序 union: 1.select的列要一样;2:order by 只放在最后一个;3不能使用distinct,因为union自动会对结果进行distinct union all 不要去除重复的行 临时表: create tempary table mytabl(name varchar(10)); select utf_8"datehoust";用utf-8编码显示字符串 rename table mytable to another; 重命名表 create (unique) index myindex using hash(using btree) on mytable(name); analysis table mytable; 更新表的索引的可压缩性 checksum table mytable;查询表的校验和 optimize table mytable;优化表的存储 checke table mytable; 检查表是否完整 repair table mytable; backup table mytable to"path"; help 'create table';