SQL:StructureQueryLanguage。(结构化查询语言)
Ps:SELECT*注意:sql语句以;结尾
使用的关键字:CREATE、ALTER、DROP
create database mydb1; Create database mydb2 character set gbk; Create database mydb3 character set gbk COLLATE gbk_chinese_ci;
查询表中的所有数据 SELECT * FROM 表名; DML 是对表中的数据进行增、删、改的操作。不要与 DDL 混淆了。 INSERT 、UPDATE、 DELETE Ps:在 mysql 中,字符串类型和日期类型都要用单引号括起来。‘tom’ ‘2015-09-04’ 空值:null
1. 插入操作:INSERT:
表一:学生表 stu
字段名称 | 字段类型 | 说明 |
---|---|---|
sid | char(6) | 学生学号 |
sname | varchar(50) | 学生姓名 |
age | int | 学生年龄 |
gender | varchar(50) | 学生性别 |
建表:
CREATE TABLE stu ( sid CHAR(6),
sname VARCHAR(50), age INT,
gender VARCHAR(50)
);
插入数据
INSERT INTO stu VALUES('S_1001', 'liuYi', 35, 'male');
INSERT INTO stu VALUES('S_1002', 'chenEr', 15, 'female');
INSERT INTO stu VALUES('S_1003', 'zhangSan', 95, 'male');
INSERT INTO stu VALUES('S_1004', 'liSi', 65, 'female');
INSERT INTO stu VALUES('S_1005', 'wangWu', 55, 'male');
INSERT INTO stu VALUES('S_1006', 'zhaoLiu', 75, 'female');
INSERT INTO stu VALUES('S_1007', 'sunQi', 25, 'male');
INSERT INTO stu VALUES('S_1008', 'zhouBa', 45, 'female');
INSERT INTO stu VALUES('S_1009', 'wuJiu', 85, 'male');
INSERT INTO stu VALUES('S_1010', 'zhengShi', 5, 'female');
INSERT INTO stu VALUES('S_1011', 'xxx', NULL, NULL);
表二:雇员表 emp
字段名称 | 字段类型 | 说明 |
---|---|---|
empno | int | 员工编号 |
ename | varchar(50) | 员工姓名 |
job | varchar(50) | 员工姓名 |
mgr | int | 员工工作 |
mgr | int | 领导编号 |
hiredate | date | 入职日期 |
sal | decimal(7,2) | 月薪 |
comm | decimal(7,2) | 奖金 |
deptno | int | 部门编号 |
建表:
CREATE TABLE emp(
empno INT, ename VARCHAR(50), job VARCHAR(50), mgr INT,
hiredate DATE,
sal DECIMAL(7,2), comm decimal(7,2), deptno INT
) ;
插入数据
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','SALESMAN',7698,'1981-02-22',1250,500,30);
INSERT INTO emp values(7566,'JONES','MANAGER',7839,'1981-04-02',2975,NULL,20);
INSERT INTO emp values(7654,'MARTIN','SALESMAN',7698,'1981-09-28',1250,1400,30);
INSERT INTO emp values(7698,'BLAKE','MANAGER',7839,'1981-05-01',2850,NULL,30);
INSERT INTO emp values(7782,'CLARK','MANAGER',7839,'1981-06-09',2450,NULL,10);
INSERT INTO emp values(7788,'SCOTT','ANALYST',7566,'1987-04-19',3000,NULL,20);
INSERT INTO emp values(7839,'KING','PRESIDENT',NULL,'1981-11-17',5000,NULL,10);
INSERT INTO emp values(7844,'TURNER','SALESMAN',7698,'1981-09-08',1500,0,30);
INSERT INTO emp values(7876,'ADAMS','CLERK',7788,'1987-05-23',1100,NULL,20);
INSERT INTO emp values(7900,'JAMES','CLERK',7698,'1981-12-03',950,NULL,30);
INSERT INTO emp values(7902,'FORD','ANALYST',7566,'1981-12-03',3000,NULL,20);
INSERT INTO emp values(7934,'MILLER','CLERK',7782,'1982-01-23',1300,NULL,10);
表三:部门表 dept
字段名称 | 字段类型 | 说明 |
---|---|---|
deptno | int | 学生学号 |
sname | varchar(50) | 部门编码 |
dname | varchar(50) | 部门名称 |
loc | varchar(50) | 部门所在地点 |
建表:
CREATE TABLE dept(
deptno INT,
dname varchar(14), loc varchar(13)
);
插入数据
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');
注:凡和聚合函数同时出现的列名,一定要写在 group by 之后
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