use Scott 使用 Scott這個數據庫
show tables;查看錶
select * from emp; 查詢emp(員工信息表)這個表
select * from dept; 查詢dept(部門信息表)這個表
select * from salgrade; 查詢salgrade(工資級別表)這個表
select enamel,sal from emp;查詢emp這個表的enamel和sal這兩列
select enamel,(sal+200)*3 newsal from emp;
select enamel, sal,comm,sal+ifnull(comm ,0) zongshouru from emp;
select distinct deptno from emp;刪除deptno這列的重複行
select * from emp where deptno=30
select * from emp where sal>3000;條件查詢
select * from emp where ename like `%TT%`;
select * from emp where ename like `_LL%`;
select * from emp where ename like `__LL%`;like模糊查詢
select * from emp where deptno=30 and sal>2000;
select * from emp where deptno=30 or sal>2000;
select * from emp where not sal>2000;
select * from emp order by sal;按照sal排序,默認是升序
select * from emp order by sal desc;按照sal降序
select * from emp order by deptno,sal;按兩列排列
select * from emp order by deptmo desc,sal desc;
select concat(ename,'\'s sal is',sal)from emp;連接
select count(*) from emp;count計數
select sum(sal),min(sal),max(sal),avg(sal) from emp;求和 最小 最大 平均
select deptno,sum(sal),min(sal),max(sal),avg(sal) from emp group by deptno;分組查詢
select ename,dname from emp , dept where emp.deptno=dept.deptno;多表查詢
select y.ename , j.ename from emp y , emp j where y.mgr=j.enpno; 自連接
select ename,sal,grade from emp,salgrade where sal between losal and hisal; between...and..查詢
select ename,dname,sal,grade from emp,dept,salgrade where emp.deptno=dept.deptno and emp.sal between losal and hisal; 三張表的連接查詢 where and
mariadb的查詢語句
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