SELECT top 1 l_title.l_id,l_title.bigclass,l_title.name,l_title.title,l_title.click,l_title.addtime, (select top 1 h_hf.addtime from h_hf where l_id=l_title.l_id order by h_hf.addtime desc,h_hf.l_id) as h_hfaddtime, (select top 1 h_hf.l_idfrom h_hf w...
(selecttop1DeptnamefromUserInfo left join Department on UserInfo.deptid=Department.DeptidwhereUserInfo.userid=AuditUserId)asdeptname, (selectisnull(SUM(iNum),0)fromCS_OrderProwhereCS_OrderPro.zid=a.ID and CS_OrderPro.codeno=a.Invno)ascgnum, (selecttop1InvNOfromCS_OrderProwhereCS_OrderPro.z...
select a.*, b.*, c.*, d.* from cttag as d left join ((ctarticle as a left join ctclass as b on a.classid=b.classid) left join ctnclass as c on a.nclassid=c.nclassid) on d.articleid=a.articleid; 显示文章表中的全部, 调用类别表中的栏目 select a.*, b.*, c.* from...
This scenario doesn't come up too often, but the other day I had a requirement to do a left join through a one to many relationship but only get 1 result from the right side of the join. This kind of scenario can often be accomplished using sub selects, but in this case I needed...
select a.nid,a.name,max(b.price) from a left join b on a.nid =b.nid group by a.nid,a.name是这样吗？
1. 2. 3. 4. 1、子查询出现在where子句中 1、查询⼯资⼤于10号部⻔的平均⼯资的⾮10号部⻔的员⼯信息 分析: 1)10号部⻔的平均⼯资 select avg(sal) from emp where deptno = 10; 2)查询员工信息 select * from emp where deptno != 10 and sal > (select avg(sal) from emp ...
今天主要分享LEFT JOIN连接类型。 01 语法结构 SELECTFROMTableAALEFTJOINTableBBONA.Key=B.Key A和B是表别名 Key是两张表的关联字段,语法结构示例只有1个,也可以是多个,用and即可。 LEFT JOIN将返回左表中的所有行和右表中匹配的行。 02 实例 这里通过表data_learning.product_order(商品销量表)、data_learnin...
1. 先连接查询 首先我们可以根据科目和成绩,来查询同一科目中分数较高的数据。 SELECT * FROM score s1 LEFT JOIN score s2 ON s1.subject_id = s2.subject_id AND s2.score > s1.score 1. 2. 3. 这样查询到的就是一个成绩记录,同一个科目全部比他分数高的成绩记录就是被关联查询出来。这里为了让第一...
这张图描述了left join(左连接)、right join(右连接) 、inner join(内连接)、outer join(外连接)相关的7种用法。 我改了一版: 感觉更方便理解了 可以关注我公众号,回复“mysql”,可以拿到高清大图 二、四种JOIN的区别 1、INNER JOIN:如果表中有至少一个匹配,则返回行; ...
16、left join:select 列名称(s) from 表名称1 left join 表名称2 on 表名称1.列名称=表名称2.列名称 ;即使右表中没有匹配,也从左表返回所有的行,表1即左表,表2即右表。 17、right join:select 列名称(s) from 表名称1 right join 表名称2 on 表名称1.列名称=表名称2.列名称 ;即使左表中没有...