数据库语句大全之联合语句UNION/内连接查询/外连接查询

1.使用联合查询：select 姓名,工资 from kaifabu union select 姓名,工资 from xiaoshoubu

2.多表联合查询： select 姓名,总成绩 from class1 where 总成绩>550 union select 姓名,总成绩 from class2 where 总成绩>550 union select 姓名,总成绩 from class3 where 总成绩>550 union select 姓名,总成绩 from class4 where 总成绩>550

3.对联合查询后的结果进行排序:select 姓名 from kjbdsjk union select 姓名 from hqage where 编号<5 order by 姓名 asc

                                                       select 姓名 from kjbdsjk union select 姓名 from hqage where 编号<5 order by 姓名 desc

4.简单内连接查询：select kj.姓名,kj.职业 from kjbdsjk as kj inner join bumenbiao as bu on bu.负责人=kj.姓名

5.复杂内连接查询：select kj.姓名,kj.性别,bu.职业名称,du.收入,du.工资,du.奖金 from (kjbdsjk as kj inner join bumenbiao as bu on kj.姓名=bu.负责人)inner join duobiao as du on du.姓名=kj.姓名

6.使用内连接选择一个表与另一个表中行相关的所有行:select kj.编号,kj.姓名,bu.职业名称 from bumenbiao as bu inner join kjbdsjk as kj on kj.姓名=bu.负责人

7.LEFT OUTER JOIN查询:select kj.编号,kj.姓名,bu.职业名称 from kjbdsjk as kj left outer join bumenbiao as bu on kj.姓名 = bu.负责人

说明左外连接查询LEFT OUTER JOIN，返回的结果是第一个表中的所有行以及第二个表中的匹配行

8.select kj.编号,bu.负责人,kj.性别,bu.职业名称 from kjbdsjk as kj right outer join bumenbiao as bu on kj.姓名=bu.负责人

说明右连接RIGHT OUTER JOIN，返回的结果是第二个表中的所有行以及第一个表中的匹配行

9.使用外连接进行多表联合查询:select kj.编号,du.姓名,kj.性别,kj.年龄,du.收入,bu.职业名称 from (kjbdsjk as kj left join duobiao as du on kj.姓名=du.姓名)left join bumenbiao as bu on kj.姓名=bu.负责人