SQL Server 2008 R2——内连接 左连接 右连接 全连接 交叉连接

Posted 2020-06-13

 SELECT * FROM Table_A
 GO
 SELECT * FROM Table_B
 GO
 
 --内连接
 SELECT a.*, b.* FROM Table_A a JOIN Table_B b ON a.ID = b.ID
 SELECT a.*, b.* FROM Table_A a INNER JOIN Table_B b ON a.ID = b.ID
 GO
 
 --内连接等价直接多表from的形式
 SELECT a.*, b.* FROM Table_A a INNER JOIN Table_B b ON a.ID = b.ID
 SELECT a.*, b.* FROM Table_A a, Table_B b WHERE a.ID = b.ID
 
 --左连接
 SELECT a.*, b.* FROM Table_A a LEFT JOIN Table_B b ON a.ID = b.ID
 SELECT a.*, b.* FROM Table_A a LEFT OUTER JOIN Table_B b ON a.ID = b.ID
 GO
 
 --右连接
 SELECT a.*, b.* FROM Table_A a RIGHT JOIN Table_B b ON a.ID = b.ID
 SELECT a.*, b.* FROM Table_A a RIGHT OUTER JOIN Table_B b ON a.ID = b.ID
 
 --A左连接B 等价于 B右连接A
 SELECT a.*, b.* FROM Table_A a LEFT JOIN Table_B b ON a.ID = b.ID
 SELECT a.*, b.* FROM Table_B b RIGHT JOIN Table_A a ON a.ID = b.ID
 
 --全连接
 SELECT a.*, b.* FROM Table_A a FULL JOIN Table_B b ON a.ID = b.ID
 SELECT a.*, b.* FROM Table_A a FULL OUTER JOIN Table_B b ON a.ID = b.ID
 
 --没有 WHERE 子句的交叉联接将产生所涉及的表的笛卡尔积。
 SELECT a.*, b.* FROM Table_A a CROSS JOIN Table_B b 
 
 --如果添加了 WHERE 子句，则交叉联接的行为将与内部联接行为相似
 SELECT a.*, b.* FROM Table_A a CROSS JOIN Table_B b WHERE  a.ID = b.ID
 SELECT a.*, b.* FROM Table_A a INNER JOIN Table_B b ON a.ID = b.ID