-- 创建EMP表

CREATE TABLE EMP

(

EMPNO int(4) PRIMARY KEY,

ENAME VARCHAR(10),

JOB VARCHAR(9),

MGR INT(4),

HIREDATE DATE,

SAL DOUBLE(7,2),

COMM DOUBLE(7,2),

DEPTNO INT(2)

);

-- where查询 语句

SELECT * from emp;

-- 模糊查询

-- 搜索emp表中还有A的员工信息

SELECT * FROM emp where ENAME like '%A%';

-- 匹配ename中用A开头的员工信息

SELECT * FROM emp where ENAME like 'A%';

-- 匹配ename中用A结尾的的员工信息

SELECT * FROM emp where ENAME like '%A';

-- 匹配ename中第二个字符为A的的员工信息

SELECT * FROM emp where ENAME like '_A%';

-- is null 判断是否为空

-- 查询所有没有加班费的员工信息

SELECT * from emp where COMM is null;

SELECT * from emp where COMM is not null;

-- 小括号，增强可阅读性

SELECT * FROM emp where ENAME='WARD' OR ENAME='ALLEN' AND SAL>7500;

SELECT * FROM emp where ENAME='WARD' OR (ENAME='ALLEN' AND SAL>7500);