oracle 基本语句练习(一) where, between ,null, like,转义字符,

1 where 筛选关键字; select * from emp where job 'CLERK' 从emp表中列出 job大于'CLERK'的项 (由于比较的是字符串,所以加单引号) 2 between and select ename,sal from emp where sal between 800 and 1500 从emp表中找到 sal在800和1500之间的项(包括800

1 where 筛选关键字;

select * from emp where job >'CLERK'

从emp表中列出 job值大于'CLERK'的项 (由于比较的是字符串,所以加单引号)

2 between and

select ename,sal from emp where sal between 800 and 1500

从emp表中找到 sal值在800和1500之间的项(包括800和1500) 列出他们的ename 和sal

3 空值

select ename,sal from emp where comm is null ;

列出非空值

select ename,sal from emp where comm is not null ;

4 模糊查询

查询ename中包含ALL的项

select ename from emp where ename like '%ALL%' ;

%代表0个或多个字符, 次查询目的为了找到ename 值为 ALL 左边和右边具有0个或多个字符的项

查询ename第二个字母为A 的项

select ename from emp where ename like '_A%' ;

5 转义字符

查找ename中带有 % 的项

select ename from emp where ename like '%$%%' escape '$' ;

指定'$'为转义字符查找% .

转义字符默认为'/' 使用/ 为转义字符时不用写后面的escape ..

6 排序order by

select * from dept order by deptno ; (默认升序)

select * from dept order by deptno desc ;(按deptno的降序排序)

组合使用:

select empno,ename from emp where empno 10 order by empno; (先过滤 再排序)

select empno,ename from emp order by empno asc,ename desc; 按(empno升序排序) empno相同时按ename 降序排序