MySQL查詢語法彙總

阿新 • • 發佈：2020-08-14

前言：

本篇文章主要簡介下MySQL中where,group by,order by,limit,join,union,union all,子表等查詢語法。

測試資料準備

create table emp (  empno numeric(4) not null,ename varchar(10),job varchar(9),mgr numeric(4),hiredate datetime,sal numeric(7,2),comm numeric(7,deptno numeric(2));
create table dept (  deptno numeric(2),dname varchar(14),loc varchar(13));
create table salgrade (  grade numeric,losal numeric,hisal numeric);
insert into dept values (10,'ACCOUNTING','NEW YORK');insert into dept values (20,'RESEARCH','DALLAS');insert into dept values (30,'SALES','CHICAGO');insert into dept values (40,'OPERATIONS','BOSTON');
insert into salgrade values (1,700,1200);insert into salgrade values (2,1201,1400);insert into salgrade values (3,1401,2000);insert into salgrade values (4,2001,3000);insert into salgrade values (5,3001,9999);
insert into emp values (7369,'SMITH','CLERK',7902,'1980-12-17',800,null,20);insert into emp values (7499,'ALLEN','SALESMAN',7698,'1981-02-20',1600,300,30);insert into emp values (7521,'WARD','1981-02-22',1250,500,30);insert into emp values (7566,'JONES','MANAGER',7839,'1981-04-02',2975,20);insert into emp values (7654,'MARTIN','1981-09-28',1400,30);insert into emp values (7698,'BLAKE','1981-05-01',2850,30);insert into emp values (7782,'CLARK','1981-06-09',2450,10);insert into emp values (7788,'SCOTT','ANALYST',7566,'1982-12-09',3000,20);insert into emp values (7839,'KING','PRESIDENT','1981-11-17',5000,10);insert into emp values (7844,'TURNER','1981-09-08',1500,30);insert into emp values (7876,'ADAMS',7788,'1983-01-12',1100,20);insert into emp values (7900,'JAMES','1981-12-03',950,30);insert into emp values (7902,'FORD',20);insert into emp values (7934,'MILLER',7782,'1982-01-23',1300,10);

1.模糊查詢

mysql> select * from emp where ename like '%S%'; +-------+-------+---------+------+---------------------+---------+------+--------+| empno | ename | job   | mgr | hiredate      | sal   | comm | deptno |+-------+-------+---------+------+---------------------+---------+------+--------+| 7369 | SMITH | CLERK  | 7902 | 1980-12-17 00:00:00 | 800.00 | NULL |   20 || 7566 | JONES | MANAGER | 7839 | 1981-04-02 00:00:00 | 2975.00 | NULL |   20 || 7788 | SCOTT | ANALYST | 7566 | 1982-12-09 00:00:00 | 3000.00 | NULL |   20 || 7876 | ADAMS | CLERK  | 7788 | 1983-01-12 00:00:00 | 1100.00 | NULL |   20 || 7900 | JAMES | CLERK  | 7698 | 1981-12-03 00:00:00 | 950.00 | NULL |   30 |+-------+-------+---------+------+---------------------+---------+------+--------+5 rows in set (0.00 sec)
mysql> select * from emp where ename like 'S%'; +-------+-------+---------+------+---------------------+---------+------+--------+| empno | ename | job   | mgr | hiredate      | sal   | comm | deptno |+-------+-------+---------+------+---------------------+---------+------+--------+| 7369 | SMITH | CLERK  | 7902 | 1980-12-17 00:00:00 | 800.00 | NULL |   20 || 7788 | SCOTT | ANALYST | 7566 | 1982-12-09 00:00:00 | 3000.00 | NULL |   20 |+-------+-------+---------+------+---------------------+---------+------+--------+2 rows in set (0.01 sec)
mysql> select * from emp where ename like '%S';+-------+-------+---------+------+---------------------+---------+------+--------+| empno | ename | job   | mgr | hiredate      | sal   | comm | deptno |+-------+-------+---------+------+---------------------+---------+------+--------+| 7566 | JONES | MANAGER | 7839 | 1981-04-02 00:00:00 | 2975.00 | NULL |   20 || 7876 | ADAMS | CLERK  | 7788 | 1983-01-12 00:00:00 | 1100.00 | NULL |   20 || 7900 | JAMES | CLERK  | 7698 | 1981-12-03 00:00:00 | 950.00 | NULL |   30 |+-------+-------+---------+------+---------------------+---------+------+--------+3 rows in set (0.00 sec)
mysql> select * from emp where ename like '_O%';+-------+-------+---------+------+---------------------+---------+------+--------+| empno | ename | job   | mgr | hiredate      | sal   | comm | deptno |+-------+-------+---------+------+---------------------+---------+------+--------+| 7566 | JONES | MANAGER | 7839 | 1981-04-02 00:00:00 | 2975.00 | NULL |   20 || 7902 | FORD | ANALYST | 7566 | 1981-12-03 00:00:00 | 3000.00 | NULL |   20 |+-------+-------+---------+------+---------------------+---------+------+--------+2 rows in set (0.00 sec)

總結：%表示任意0個或多個字元，可匹配任意型別和長度的字元；_表示任意單個字元，匹配單個任意字元。

2.排序

mysql> select * from emp order by sal;+-------+--------+-----------+------+---------------------+---------+---------+--------+| empno | ename | job    | mgr | hiredate      | sal   | comm  | deptno |+-------+--------+-----------+------+---------------------+---------+---------+--------+| 7369 | SMITH | CLERK   | 7902 | 1980-12-17 00:00:00 | 800.00 |  NULL |   20 || 7900 | JAMES | CLERK   | 7698 | 1981-12-03 00:00:00 | 950.00 |  NULL |   30 || 7876 | ADAMS | CLERK   | 7788 | 1983-01-12 00:00:00 | 1100.00 |  NULL |   20 || 7521 | WARD  | SALESMAN | 7698 | 1981-02-22 00:00:00 | 1250.00 | 500.00 |   30 || 7654 | MARTIN | SALESMAN | 7698 | 1981-09-28 00:00:00 | 1250.00 | 1400.00 |   30 || 7934 | MILLER | CLERK   | 7782 | 1982-01-23 00:00:00 | 1300.00 |  NULL |   10 || 7844 | TURNER | SALESMAN | 7698 | 1981-09-08 00:00:00 | 1500.00 |  0.00 |   30 || 7499 | ALLEN | SALESMAN | 7698 | 1981-02-20 00:00:00 | 1600.00 | 300.00 |   30 || 7782 | CLARK | MANAGER  | 7839 | 1981-06-09 00:00:00 | 2450.00 |  NULL |   10 || 7698 | BLAKE | MANAGER  | 7839 | 1981-05-01 00:00:00 | 2850.00 |  NULL |   30 || 7566 | JONES | MANAGER  | 7839 | 1981-04-02 00:00:00 | 2975.00 |  NULL |   20 || 7788 | SCOTT | ANALYST  | 7566 | 1982-12-09 00:00:00 | 3000.00 |  NULL |   20 || 7902 | FORD  | ANALYST  | 7566 | 1981-12-03 00:00:00 | 3000.00 |  NULL |   20 || 7839 | KING  | PRESIDENT | NULL | 1981-11-17 00:00:00 | 5000.00 |  NULL |   10 |+-------+--------+-----------+------+---------------------+---------+---------+--------+14 rows in set (0.00 sec)
mysql> select * from emp order by sal asc;+-------+--------+-----------+------+---------------------+---------+---------+--------+| empno | ename | job    | mgr | hiredate      | sal   | comm  | deptno |+-------+--------+-----------+------+---------------------+---------+---------+--------+| 7369 | SMITH | CLERK   | 7902 | 1980-12-17 00:00:00 | 800.00 |  NULL |   20 || 7900 | JAMES | CLERK   | 7698 | 1981-12-03 00:00:00 | 950.00 |  NULL |   30 || 7876 | ADAMS | CLERK   | 7788 | 1983-01-12 00:00:00 | 1100.00 |  NULL |   20 || 7521 | WARD  | SALESMAN | 7698 | 1981-02-22 00:00:00 | 1250.00 | 500.00 |   30 || 7654 | MARTIN | SALESMAN | 7698 | 1981-09-28 00:00:00 | 1250.00 | 1400.00 |   30 || 7934 | MILLER | CLERK   | 7782 | 1982-01-23 00:00:00 | 1300.00 |  NULL |   10 || 7844 | TURNER | SALESMAN | 7698 | 1981-09-08 00:00:00 | 1500.00 |  0.00 |   30 || 7499 | ALLEN | SALESMAN | 7698 | 1981-02-20 00:00:00 | 1600.00 | 300.00 |   30 || 7782 | CLARK | MANAGER  | 7839 | 1981-06-09 00:00:00 | 2450.00 |  NULL |   10 || 7698 | BLAKE | MANAGER  | 7839 | 1981-05-01 00:00:00 | 2850.00 |  NULL |   30 || 7566 | JONES | MANAGER  | 7839 | 1981-04-02 00:00:00 | 2975.00 |  NULL |   20 || 7788 | SCOTT | ANALYST  | 7566 | 1982-12-09 00:00:00 | 3000.00 |  NULL |   20 || 7902 | FORD  | ANALYST  | 7566 | 1981-12-03 00:00:00 | 3000.00 |  NULL |   20 || 7839 | KING  | PRESIDENT | NULL | 1981-11-17 00:00:00 | 5000.00 |  NULL |   10 |+-------+--------+-----------+------+---------------------+---------+---------+--------+14 rows in set (0.00 sec)
mysql> select * from emp order by sal desc;+-------+--------+-----------+------+---------------------+---------+---------+--------+| empno | ename | job    | mgr | hiredate      | sal   | comm  | deptno |+-------+--------+-----------+------+---------------------+---------+---------+--------+| 7839 | KING  | PRESIDENT | NULL | 1981-11-17 00:00:00 | 5000.00 |  NULL |   10 || 7788 | SCOTT | ANALYST  | 7566 | 1982-12-09 00:00:00 | 3000.00 |  NULL |   20 || 7902 | FORD  | ANALYST  | 7566 | 1981-12-03 00:00:00 | 3000.00 |  NULL |   20 || 7566 | JONES | MANAGER  | 7839 | 1981-04-02 00:00:00 | 2975.00 |  NULL |   20 || 7698 | BLAKE | MANAGER  | 7839 | 1981-05-01 00:00:00 | 2850.00 |  NULL |   30 || 7782 | CLARK | MANAGER  | 7839 | 1981-06-09 00:00:00 | 2450.00 |  NULL |   10 || 7499 | ALLEN | SALESMAN | 7698 | 1981-02-20 00:00:00 | 1600.00 | 300.00 |   30 || 7844 | TURNER | SALESMAN | 7698 | 1981-09-08 00:00:00 | 1500.00 |  0.00 |   30 || 7934 | MILLER | CLERK   | 7782 | 1982-01-23 00:00:00 | 1300.00 |  NULL |   10 || 7521 | WARD  | SALESMAN | 7698 | 1981-02-22 00:00:00 | 1250.00 | 500.00 |   30 || 7654 | MARTIN | SALESMAN | 7698 | 1981-09-28 00:00:00 | 1250.00 | 1400.00 |   30 || 7876 | ADAMS | CLERK   | 7788 | 1983-01-12 00:00:00 | 1100.00 |  NULL |   20 || 7900 | JAMES | CLERK   | 7698 | 1981-12-03 00:00:00 | 950.00 |  NULL |   30 || 7369 | SMITH | CLERK   | 7902 | 1980-12-17 00:00:00 | 800.00 |  NULL |   20 |+-------+--------+-----------+------+---------------------+---------+---------+--------+14 rows in set (0.00 sec)

總結：order by排序預設按asc升序來排列也可指定desc降序排列

3.限制多少行

mysql> select * from emp limit 3;+-------+-------+----------+------+---------------------+---------+--------+--------+| empno | ename | job   | mgr | hiredate      | sal   | comm  | deptno |+-------+-------+----------+------+---------------------+---------+--------+--------+| 7369 | SMITH | CLERK  | 7902 | 1980-12-17 00:00:00 | 800.00 |  NULL |   20 || 7499 | ALLEN | SALESMAN | 7698 | 1981-02-20 00:00:00 | 1600.00 | 300.00 |   30 || 7521 | WARD | SALESMAN | 7698 | 1981-02-22 00:00:00 | 1250.00 | 500.00 |   30 |+-------+-------+----------+------+---------------------+---------+--------+--------+3 rows in set (0.00 sec)
mysql> select * from emp order by sal desc limit 3;+-------+-------+-----------+------+---------------------+---------+------+--------+| empno | ename | job    | mgr | hiredate      | sal   | comm | deptno |+-------+-------+-----------+------+---------------------+---------+------+--------+| 7839 | KING | PRESIDENT | NULL | 1981-11-17 00:00:00 | 5000.00 | NULL |   10 || 7902 | FORD | ANALYST  | 7566 | 1981-12-03 00:00:00 | 3000.00 | NULL |   20 || 7788 | SCOTT | ANALYST  | 7566 | 1982-12-09 00:00:00 | 3000.00 | NULL |   20 |+-------+-------+-----------+------+---------------------+---------+------+--------+3 rows in set (0.00 sec)

總結：limit限定顯示前多少行，可與order by聯合使用

4.聚合函

count() sum()函式用法：#1.各個部門的薪水和mysql> select deptno,sum(sal) from emp group by deptno;+--------+----------+| deptno | sum(sal) |+--------+----------+|   10 | 8750.00 ||   20 | 10875.00 ||   30 | 9400.00 |+--------+----------+3 rows in set (0.01 sec)
#2.group by欄位必須出現在select欄位後面  各個部門的各個崗位的薪水和mysql> select deptno,job,sum(sal) from emp group by deptno,job;+--------+-----------+----------+| deptno | job    | sum(sal) |+--------+-----------+----------+|   10 | CLERK   | 1300.00 ||   10 | MANAGER  | 2450.00 ||   10 | PRESIDENT | 5000.00 ||   20 | ANALYST  | 6000.00 ||   20 | CLERK   | 1900.00 ||   20 | MANAGER  | 2975.00 ||   30 | CLERK   |  950.00 ||   30 | MANAGER  | 2850.00 ||   30 | SALESMAN | 5600.00 |+--------+-----------+----------+9 rows in set (0.01 sec)
#3.having  薪水和>5000的各個部門的各個崗位mysql> select deptno,sum(sal)   -> from emp   -> group by deptno,job  -> having sum(sal)>5000; +--------+----------+----------+| deptno | job   | sum(sal) |+--------+----------+----------+|   20 | ANALYST | 6000.00 ||   30 | SALESMAN | 5600.00 |+--------+----------+----------+2 rows in set (0.00 sec)#4.常用組合where order limit select deptno,sum(sal) as sum_salfrom emp where job='SALESMAN'group by deptno,jobhaving sum(sal)>5000 order by sum(sal) desc limit 1;

下面介紹下join及union的用法
資料準備：

create table testa(aid int,aname varchar(40));
create table testb(bid int,bname varchar(40),age int);
insert into testa values(1,'xiaoming');insert into testa values(2,'LY');insert into testa values(3,'KUN');insert into testa values(4,'ZIDONG');insert into testa values(5,'HB');

insert into testb values(1,'xiaoming',10);insert into testb values(2,'LY',100);insert into testb values(3,'KUN',200);insert into testb values(4,'ZIDONG',110);insert into testb values(6,'niu',120);insert into testb values(7,'meng',130);insert into testb values(8,'mi',170);

5.left join

mysql> select  -> a.aid,a.aname,-> b.bid,b.bname,b.age  -> from testa as a  -> left join testb as b on a.aid=b.bid; +------+----------+------+----------+------+| aid | aname  | bid | bname  | age |+------+----------+------+----------+------+|  1 | xiaoming |  1 | xiaoming |  10 ||  2 | LY    |  2 | LY    | 100 ||  3 | KUN   |  3 | KUN   | 200 ||  4 | ZIDONG  |  4 | ZIDONG  | 110 ||  5 | HB    | NULL | NULL   | NULL |+------+----------+------+----------+------+5 rows in set (0.00 sec)

總結：a left join b a表全，用b表去匹配a表LEFT JOIN 關鍵字會從左表 (a) 那裡返回所有的行，即使在右表 (b) 中沒有匹配的行,匹配不到的列用NULL代替

6.right join

mysql> select  -> a.aid,b.age  -> from testa as a  -> right join testb as b on a.aid=b.bid;+------+----------+------+----------+------+| aid | aname  | bid | bname  | age |+------+----------+------+----------+------+|  1 | xiaoming |  1 | xiaoming |  10 ||  2 | LY    |  2 | LY    | 100 ||  3 | KUN   |  3 | KUN   | 200 ||  4 | ZIDONG  |  4 | ZIDONG  | 110 || NULL | NULL   |  6 | niu   | 120 || NULL | NULL   |  7 | meng   | 130 || NULL | NULL   |  8 | mi    | 170 |+------+----------+------+----------+------+7 rows in set (0.00 sec)

總結：a right join b b表全，用a表去匹配b表RIGHT JOIN 關鍵字會右表 (b) 那裡返回所有的行，即使在左表 (a) 中沒有匹配的行,匹配不到的列用NULL代替

7.inner join

mysql> select  -> a.aid,b.age  -> from testa as a  -> inner join testb as b on a.aid=b.bid; +------+----------+------+----------+------+| aid | aname  | bid | bname  | age |+------+----------+------+----------+------+|  1 | xiaoming |  1 | xiaoming |  10 ||  2 | LY    |  2 | LY    | 100 ||  3 | KUN   |  3 | KUN   | 200 ||  4 | ZIDONG  |  4 | ZIDONG  | 110 |+------+----------+------+----------+------+4 rows in set (0.00 sec)
mysql> select  -> a.aid,b.age  -> from testa as a  -> join testb as b on a.aid=b.bid; +------+----------+------+----------+------+| aid | aname  | bid | bname  | age |+------+----------+------+----------+------+|  1 | xiaoming |  1 | xiaoming |  10 ||  2 | LY    |  2 | LY    | 100 ||  3 | KUN   |  3 | KUN   | 200 ||  4 | ZIDONG  |  4 | ZIDONG  | 110 |+------+----------+------+----------+------+4 rows in set (0.00 sec)

總結：inner join 與join 效果一樣在表中存在至少一個匹配時，INNER JOIN 關鍵字返回行

8.union與union all

mysql> select aid,aname from testa  -> union  -> select bid,bname from testb;+------+----------+| aid | aname  |+------+----------+|  1 | xiaoming ||  2 | LY    ||  3 | KUN   ||  4 | ZIDONG  ||  5 | HB    ||  6 | niu   ||  7 | meng   ||  8 | mi    |+------+----------+8 rows in set (0.01 sec)
mysql> select aid,aname from testa  -> union all  -> select bid,bname from testb;+------+----------+| aid | aname  |+------+----------+|  1 | xiaoming ||  2 | LY    ||  3 | KUN   ||  4 | ZIDONG  ||  5 | HB    ||  1 | xiaoming ||  2 | LY    ||  3 | KUN   ||  4 | ZIDONG  ||  6 | niu   ||  7 | meng   ||  8 | mi    |+------+----------+12 rows in set (0.00 sec)

總結：union 會去重 union all不去重

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