3表联查的sql语句语法

两种:1.select * from 表1,表2,表3 where 表1.字段=表2.字段 and 表1.字段=表3.字段 这种效率比较低 结构简单数据量小可以采用2.select * from 表1 join 表2 on 表1.字段=表2.字段 and join 表3 on 表1.字段=表3.字段 这个不错

车讯语句:select username,psw from (a1 left join a2 on a1.a1_id=a2.a1_id) left join a3 on a1.a1_id=a3.a1_id 这样写:SELECT S.SName AS 姓名, CS.CourseName AS 课程, C.Score AS 成绩 FROM Students AS S INNER JOIN Score AS C

这问题交给我吧,假设学生表叫student,课程表叫class,选课表叫choose1.三层嵌套的问题 select student.name from student where student.id IN (select choose.sid from choose where choose.cid NOT IN (select class.id from class where class.

用inner join on 加上条件!把符合条件的都查询出来放到一个集合中!在写一个方法进行数据累加并保存!就OK了

sql="select username,psw,gname,tel from (t1 left join t2 on t1.t1_id=t2.t1_id) left join t3 on t1.t1_id=t3.t1_id" 详细出处参考:http://www.jb51.net/article/15893.htm

select a.*,b.*c.* from table1 a,table2 b,table3 c where a.aid=b.bid and b.bid=c.cid

Select * from a , b ,c where a.column1 = b.column1 and b.column2 = c.column2当然.左连接也是可以的关联条件必须>=表数-1

select a.no,a.name,b.subid,b.subname,c.score from a,b,c where a.no = c.no and b.subid = c.subid ;

select E.id,E.name,E.gender,E.birthday,sum(S.salary),D.deptname from Employee E inner join Salaryrecord S on E.id=S.id and S.sdate>CONVERT(Date,'2012') and S.sdate<CONVERT(Date,'2013') inner join Department D on E.deptid=D.deptid

Select a.*,c.temperature_alarm_gradient From ugp_check_node as a Inner Join ugp_converge_node as b On a.id=b.id Inner Join ugp_converge_node_config as c On a.id=c.id个人觉得,b里面应该复是没有id的,应该是b里面有个列与制a相关另一个列与c相关,a与c没关系,这样才会出现百3表关联的需求,不然又不度查b 那么这个查询跟b就没什么关系了

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