sql92和sql99的區別

sql92和sql99比較

1.功能方面：sql99支持的較多
2.可讀性：sql99實現了鏈接條件和篩選條件的分離，所以可讀性較高。
java

SQL92和SQL99都是用來表示多表的聯合查詢使用的，二者在開發中，具體使用哪種都是能夠的，可是在書寫和閱讀的過程當中，具體表如今如下：sql

一、笛卡爾積中的區別spa

①SQL92中的笛卡爾積：select * from emp,dept

②SQL99中的笛卡爾積：select * from emp cross join dept

二、等值鏈接方面的區別.net

①SQL92表示：select * from emp,dept where emp.deptno=dept.deptno

②SQL99表示：select * from emp innner join dept on emp.deptno=dept.deptno

三、不等值鏈接方面code

```java
①SQL92表示：select * from emp ,salgrade where emp.sal<=salgrade.hisal and emp.sal>=salgrade.losal

②SQL99表示：select * from emp inner join dept on emp.deptno=dept.deptno where sal>2000

四、左外鏈接blog

①SQL表示：select * from emp ,dept where emp.deptno=dept.depetno(+)

②SQL99表示：select * from emp left outer join dept on emp.deptno=dept.deptno

五、右外鏈接ci

①SQL92實現：select * from emp ,depet where emp.deptno = dept.deptno;

②SQL99實現：select * from emp  righ outer join dept on emp.deptno=dept.deptno

六、全完鏈接開發

①SQL92實現：select * from emp,dept where epm.deptno(+) = dept.dpetno(+)

②SQL99實現：select * from emp full outer join dept on emp.deptno=dept.deptno;

七、自鏈接it

①SQL92實現：select e1.*,e2.ename from emp e1,emp e2 where e1.deptno=e2.deptno

②SQL99實現：select e1.*,e2.ename from emp e1 inner join emp e2 on e1.deptno=e2.deptno

八、在三表鏈接查詢中class

①SQL92實現：

select e.*,d.dname,c.cname 
        from emp e,dept d,city c
        where (e.deptno=d.deptno and d.loc=c.cid and sal>2000) or (e.deptno=d.deptno and d.loc=c.cid and comm is not null) 
        order by e.sal 
②SQL99實現：

select * from emp e 
      inner join dept d 
      on e.deptno = d.deptno 
      inner join city c 
      on d.loc =c.cid
      where e.sal>2000 or e.comm is not null
      order by e.sal

此外，SQL99中在內鏈接中還可使用關鍵字:using

select * from emp inner join dept using(deptno)

部分轉載自：

https://blog.csdn.net/wyqwilliam/article/details/103076797?utm_medium=distribute.pc_relevant.none-task-blog-BlogCommendFromBaidu-1.control&depth_1-utm_source=distribute.pc_relevant.none-task-blog-BlogCommendFromBaidu-1.control