#同时查询多张表

#同时查询多张表

SELECT * FROM 表1，表2 ...表n WHERE 条件
#例如
SELECT u.id,temp.zui FROM ht_user u,(SELECT min(mobile) as zui FROM ht_user) temp
WHERE u.mobile=temp.zui

SELECT u.id,t.zui FROM ht_user u,(SELECT MAX(user_id) as zui FROM ht_trade_log) t
WHERE u.id = t.zui

SELECT u.* FROM ht_user u,(SELECT MAX(user_id) as zui FROM ht_trade_log) t
WHERE u.id = t.zui


SELECT d.deptName,e.salary,e.empName  FROM emp e(SELECT id FROM dept  WHERE id = 1) d
WHERE d.id = e.deptid;
#第一种方法
SELECT e.salary,e.deptID FROM dept d,emp e WHERE d.id = e.deptid and d.detname in('测试','开发');


#第二种方法
#UNION 可以将两个查询结果合并要求查询数据表结构一致
#UNION ALL 查询结果不会去除一致数据
#UNION 可以自动去重
SELECT e.salary,e.deptID FROM dept d,emp e WHERE d.id = e.deptid and d.deptName='测试'
UNION
SELECT e.salary,e.deptID FROM dept d,emp e WHERE d.id = e.deptid and d.deptName='开发'