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