首先创建一个数据库 d1 然后创建一个表,表的内容如下:
CREATE TABLE `emp` (
`empno` int(4) NOT NULL, --约束不为空
`ename` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL, --字符集和校对字符集
`job` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,
`mgr` int(4) NULL DEFAULT NULL,
`hiredate` date NOT NULL,
`sai` int(255) NOT NULL,
`comm` int(255) NULL DEFAULT NULL,
`deptno` int(2) NOT NULL,
PRIMARY KEY (`empno`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic; --存储引擎
“row_format = dynamic” 是 MySQL 中用于设置表格行格式的一种选项。 它表示表格的行格式是动态的,即每一行可以根据需要使用不同的格式。 当使用 “row_format = dynamic” 时,MySQL 会自动根据每一行的实际长度选择最适合的行格式,可以是 “fixed”、“dynamic” 或 “compressed”。
表的内容如下:
INSERT INTO `emp` VALUES (1001, '甘宁', '文员', 1013, '2000-12-17', 8000, NULL, 20);
INSERT INTO `emp` VALUES (1002, '黛绮丝', '销售员', 1006, '2001-02-20', 16000, 3000, 30);
INSERT INTO `emp` VALUES (1003, '殷天正', '销售员', 1006, '2001-02-22', 12500, 5000, 30);
INSERT INTO `emp` VALUES (1004, '刘备', '经理', 1009, '2001-04-02', 29750, NULL, 20);
INSERT INTO `emp` VALUES (1005, '谢逊', '销售员', 1006, '2001-09-28', 12500, 14000, 30);
INSERT INTO `emp` VALUES (1006, '关羽', '经理', 1009, '2001-05-01', 28500, NULL, 30);
INSERT INTO `emp` VALUES (1007, '张飞', '经理', 1009, '2001-09-01', 24500, NULL, 10);
INSERT INTO `emp` VALUES (1008, '诸葛亮', '分析师', 1004, '2007-04-19', 30000, NULL, 20);
INSERT INTO `emp` VALUES (1009, '曾阿牛', '董事长', NULL, '2001-11-17', 50000, NULL, 10);
INSERT INTO `emp` VALUES (1010, '韦一笑', '销售员', 1006, '2001-09-08', 15000, 0, 30);
INSERT INTO `emp` VALUES (1011, '周泰', '文员', 1006, '2007-05-23', 11000, NULL, 20);
INSERT INTO `emp` VALUES (1012, '程普', '文员', 1006, '2001-12-03', 9500, NULL, 30);
INSERT INTO `emp` VALUES (1013, '庞统', '分析师', 1004, '2001-12-03', 30000, NULL, 20);
INSERT INTO `emp` VALUES (1014, '黄盖', '文员', 1007, '2002-01-23', 13000, NULL, 10);
INSERT INTO `emp` VALUES (1015, '张三', '保洁员', 1001, '2013-05-01', 80000, 50000, 50);
mysql> select ename from emp where deptno=30;
mysql> select ename, empno,deptno from emp where job="销售员";
mysql> select ename,sai, comm from emp where comm>sai;
mysql> select ename,sai, comm from emp where comm>sai*1.6;
mysql> select * from emp where deptno=10 and job="经理" or deptno=20 and job="销售员";
mysql> select * from emp where deptno=10 and job="经理" or deptno=20 and job="销售员" or job!="销售员" and job!="经理" and sai>=20000;^C
mysql> select * from emp where deptno=10 and job="经理"
-> or deptno=20 and job="销售员"
-> or job!="销售员" and job!="经理" and sai>=20000;
mysql> select ename from emp where comm is null or sai<1000;
– 注意:一个汉字占三个字节
mysql> select ename from emp where length(ename)>=9;
length(ename) 判断中文所占字节长度
mysql> select ename from emp where hiredate like "2000%";
mysql> select * from emp order by empno ASC;
mysql> select * from emp order by sai desc,hiredate ASC;
mysql> select deptno,AVG(sai) from emp group by deptno;
mysql> select deptno,count(ename) from emp group by deptno;
mysql> select job,max(sai),min(sai),count(ename) from emp group by job;
mysql> select name,group_concat(ename) from emp3 e,dept3 d where e.dept_id=d.deptno group by name;
group_concat 函数可以把每个分组的字段值都显示出来。
mysql> select name,group_concat(ename) from emp3 e,dept3 d where e.dept_id=d.deptno and name="研发部" group by name;
mysql> select name,group_concat(ename) from emp3, dept3 where emp3.dept_id=dept3.deptno and name in ('研发部','销售部')group by name;
mysql> select name,count(ename) from emp3 e,dept3 d where e.dept_id=d.deptno group by name order by count(ename) asc;
mysql> select name,count(ename) from emp3 e,dept3 d where e.dept_id=d.deptno group by name having count(ename)>=3 oreder by count(ename) desc;