sql join 的语句怎么写? 这种SQL语句该怎么写?好像说是要用到Join

SQL\u8bed\u53e5\u5982\u4f55\u4f7f\u7528join?

join\u5206\u4e3aleft join, inner join, right join\uff0c \u9ed8\u8ba4\u662finner join
left join \u8868\u793a\u7ed3\u679c\u5df2\u5de6\u4fa7\u4e3a\u51c6\uff0c\u5f53\u53f3\u4fa7\u6ca1\u6709\u5de6\u4fa7\u7684\u8bb0\u5f55\u662f\uff0c\u5b57\u6bb5\u503c\u5df2null\u8868\u793a
right join \u8868\u793a\u7ed3\u679c\u5df2\u53f3\u4fa7\u4e3a\u51c6\uff0c\u5f53\u5de6\u4fa7\u6ca1\u6709\u53f3\u4fa7\u7684\u8bb0\u5f55\u662f\uff0c\u5b57\u6bb5\u503c\u5df2null\u8868\u793a
inner join \u8868\u793a\u83b7\u53d6\u4e24\u4e2a\u8868\u7684\u5171\u6709\u8bb0\u5f55\uff0c\u548c\u8fde\u8868\u67e5\u8be2\u76f8\u540c

select id,name,title,type1 from table1
join
select type2 from table2
on table1.id=table2.id

select cm.Id, n.nName, cm.cName from Name as n, curriculum as cm, Cn as cwhere cm.NameId = n.Id and c.curriculumId = cm.Id
Method 2:
select cm.Id, n.nName, cm.cName from curriculum as cminner join Name as non cm.NameId = n.Idinner join Cn as con c.curriculumId = cm.Id

内链接(inner join):
内连接INNER JOIN是最常用的连接操作。从数学的角度讲就是求两个表的交集,从笛卡尔积的角度讲就是从笛卡尔积中挑出ON子句条件成立的记录。
左链接(left join):
左链接LEFT JOIN的含义就是求两个表的交集外加左表剩下的数据。依旧从笛卡尔积的角度讲,就是先从笛卡尔积中挑出ON子句条件成立的记录,然后加上左表中剩余的记录。
右链接(right join):
右链接RIGHT JOIN就是求两个表的交集外加右表剩下的数据。再次从笛卡尔积的角度描述,右连接就是从笛卡尔积中挑出ON子句条件成立的记录,然后加上右表中剩余的记录
左外链接(left outter join):
左外链接left outter join就是求左表去除两个表的交集部分剩下数据。
右外链接(right outter join):
右外链接right outter join就是求右表去除两个表的交集部分剩下数据。

select a.NAME,ISNULL(a.HOURS,"/") as HOURS ,b.CATECOPY,b.RANK from table1 as a left join table2 as b on a.NAME=b.NAME and a.CATECOPY=b.CATECOPY

扩展阅读:sql中的join on用法 ... sql join on 多表链接 ... join的四种用法 ... join in 和join区别 ... sql join on 三表连接 ... sql语句inner join详解 ... sql关联语句join用法 ... sql full join 全连接 ... join的用法顺口溜 ...

本站交流只代表网友个人观点,与本站立场无关
欢迎反馈与建议,请联系电邮
2024© 车视网