www.4585.net > mysql 联合

mysql 联合

联合索引是由多个字段组成的索引。CREATE [UNIQUE|FULLTEXT|SPATIAL] INDEX index_name[USING index_type]ON tbl_name (index_col_name,...)index_col_name:col_name [(length)] [ASC | DESC] 如果你经常要用到多个字段的多条件查询,可以考虑建...

一使用SELECT子句进行多表查询 SELECT 字段名 FROM 表1,表2 … WHERE 表1.字段 = 表2.字段 AND 其它查询条件 SELECT a.id,a.name,a.address,a.date,b.math,b.english,b.chinese FROM tb_demo065_tel AS b,tb_demo065 AS a WHERE a.id=b.id 注:在...

这简答 select 人员,count(1) as 产量 from ( select 人员,产量 from 表1 union all select 人员,产量 from 表2 ) t group by 人员

这么写: select uid,name,max(dateline) dateline from a,b where a.uid = b.uid group by uid,name order by max(dateline)

Mysql多表联合索引: 1、多表联合索引在查询语句中能加速查询速度。select * from table1,table2 where table1.id = table2.id。 2、多表联合的索引的sql语法,一个user表有4个字段 id name age sex,分别给name age sex建立三个单独的索引,此时...

SELECT m.user_id, b_total, c_total, d_total FROM a m, (SELECT user_id, COUNT(*) b_total FROM b GROUP BY user_id) n, (SELECT user_id, COUNT(*) c_total FROM c GROUP BY user_id) j, (SELECT user_id, COUNT(*) d_total FROM d GROUP BY...

SELECT shop.id,shop.`name`,card.id as cid,card.sid,card.cname FROM shop , card WHERE shop.id = card.sid 这是一种最直白的方式查询方式,也可以用join

SELECT A.ID, A.NUMBER, A.PRICE, A.ORDER_TIME, B.USER_ID, B.STARTIME, B.STOPTIME, C.CHANNEL_PAY, D.COMPANY FROM D表 D LEFT JOIN A表 A ON A.COMPANY_ID = D.UID LEFT JOIN B表 B ON B.COMPANY_ID = D.UID LEFT JOIN C表 C ON C.COMPANY_I...

如果是对多个列增加 UNIQUE 约束,通过 ADD UNIQUE KEY 处理。 mysql> CREATE TABLE test_unique( -> id INT, -> name VARCHAR(10), -> value VARCHAR(10) -> ); Query OK, 0 rows affected (0.08 sec) mysql> ALTER TABLE test_unique -> ADD U...

---table1指的是第一张表,table2指的是第二张表,table3指的是第三张表,select a.uid,a.uname,a.upsw,a.urealname,a.utel,a.remark,b.rname,b.rremark,c.deptname,c.deptremark from table1 a,table2 b, table3 c where a.sems_role_rid=b.rid...

网站地图

All rights reserved Powered by www.4585.net

copyright ©right 2010-2021。
www.4585.net内容来自网络,如有侵犯请联系客服。zhit325@qq.com