SQL中cross join,left join,right join ,full join,inner join 的区别
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cross join 是笛卡儿乘积 就是一张表的行数乘以另一张表的行数
left join 第一张表的连接列在第二张表中没有匹配是,第二张表中的值返回null
right join 第二张表的连接列在第一张表中没有匹配是,第一张表中的值返回null
full join 返回两张表中的行 left join+right join
inner join 只返回两张表连接列的匹配项
- SQL中cross join,left join,right join ,full join,inner join 的区别
- SQL中cross join,left join,right join ,full join,inner join 的区别
- SQL中cross join,left join,right join ,full join,inner join 的区别
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- left join,inner join,right join,cross join,full join的区别[转载]
- left join,inner join,right join,cross join,full join的区别[转载]
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