1  /*  左连接 left join 或者 left outer join   */ 2  /* 左连接 Table_A表数据全部显示，Table_B根据条件匹配Table_A 匹配上显示，否则显示NULL */ 3  SELECT * from Table_A 4  SELECT * from Table_B 5  SELECT * from Table_A a  left outer join Table_B b on a.Code = b.Code 6   7   8   9  /*  右连接 right join 或者 right outer join   */10  /* 右连接 Table_B表数据全部显示，Table_A根据条件匹配Table_B 匹配上显示，否则显示NULL */11  SELECT * from Table_A12  SELECT * from Table_B13  SELECT * from Table_A a right join Table_B b on a.Code = b.Code14  15  16  /*完整外部联接:full join或full outer join*/17  /*完整外部联接返回Table_A和Table_b中的所有行。当Table_A在Table_B表中没有匹配行时，18  则Table_B的选择列表列包含空值。如果表之间有匹配行，则整个结果集行包含基表的数据值。*/19  SELECT * from Table_A20  SELECT * from Table_B21  SELECT * from Table_A a full join Table_B b on a.Code = b.Code22  23 /*内连接:join或 inner join*/24 /*返回Table_A和Table_B中匹配的列*/25  SELECT * from Table_A26  SELECT * from Table_B27  SELECT * from Table_A a  join Table_B b on a.Code = b.Code28  29  /* 交差连接 cross join */30  /*交差连接返回的结果是 Table_A 和Table_B表的笛卡尔积(Table_A的行数乘以Table_B的行数) */31  SELECT * from Table_A32  SELECT * from Table_B33  SELECT Count(*) from Table_A a cross join Table_B 34  SELECT * from Table_A a cross join Table_B