mysql 常用的有用命令2
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 monthinterval 5 yearaddtime(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： escapeselect * 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';?