SQL SERVER复习笔记(四)(二)
连接,相当于先进行自然连接,然后将右表不匹配的行添加进自然连接结果集里,用空值来填充左表
select book1.*,作者姓名,职称,联系电话 from book1 RIGHT OUTER JOIN teacher
ON book1.编号=teacher.编号
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--(7)全外连接,左右表空值都填充进来
select book1.*,作者姓名,职称,联系电话 from book1 FULL JOIN teacher
ON book1.编号=teacher.编号
select * from book1,teacher
--十.exists和in
select 编号,书名,定价 from book1
where exists (select 编号 from teacher)
select * from teacher
select 编号,书名,定价 from book1
where 编号 in (select 编号 from teacher)