数据库之表的查询方式

一：where查询方式

（1）书写顺序:

例如：

select id,name from emp where id > 3 and id < 6;

（2）执行顺序:

　　（1）from :确定查询那个表

　　（2）where:筛选数据查找条件

　　（3）select:从筛选出来的数据条件中取出数据

（3）练习:

create table emp(
  id int not null unique auto_increment,
  name varchar(20) not null,
  sex enum('male','female') not null default 'male', #大部分是男的
  age int(3) unsigned not null default 28,
  hire_date date not null,
  post varchar(50),
  post_comment varchar(100),
  salary double(15,2),
);


#三个部门：教学，销售，运营
insert into emp(name,sex,age,hire_date,post,salary,office,depart_id) values
('jason','male',18,'20170301','张江第一帅形象代言',7300.33,401,1), #以下是教学部
('egon','male',78,'20150302','teacher',1000000.31,401,1),
('kevin','male',81,'20130305','teacher',8300,401,1),
('tank','male',73,'20140701','teacher',3500,401,1),
('owen','male',28,'20121101','teacher',2100,401,1),
('jerry','female',18,'20110211','teacher',9000,401,1),
('nick','male',18,'19000301','teacher',30000,401,1),
('sean','male',48,'20101111','teacher',10000,401,1),

('歪歪','female',48,'20150311','sale',3000.13,402,2),#以下是销售部门
('丫丫','female',38,'20101101','sale',2000.35,402,2),
('丁丁','female',18,'20110312','sale',1000.37,402,2),
('星星','female',18,'20160513','sale',3000.29,402,2),
('格格','female',28,'20170127','sale',4000.33,402,2),

('张野','male',28,'20160311','operation',10000.13,403,3), #以下是运营部门
('程咬金','male',18,'19970312','operation',20000,403,3),
('程咬银','female',18,'20130311','operation',19000,403,3),
('程咬铜','male',18,'20150411','operation',18000,403,3),
('程咬铁','female',18,'20140512','operation',17000,403,3)
;

表格建立及数据插入

# 1.查询id大于等于3小于等于6的数据
select * from emp where id >= 3 and id <= 6;
select name,salary from emp where id between 3 and 6;  # 查询id(3-6)之间姓名 薪资

# 2.查询薪资是20000或者18000或者17000的数据
select * from emp where salary = 20000 or salary = 18000 or salary = 17000;
select name,id from emp where salary in (20000,18000,17000); 查看薪资在（20000 180000 17000）姓名 ID


# 3.查询员工姓名中包含o字母的员工姓名和薪资

select name,id from emp where name like '%o%';   # 模糊匹配 匹配出所有含有o字母

# 4.查询员工姓名是由四个字符组成的员工姓名与其薪资
select name,salary from emp where name like '____';
select name,salary,id from emp where  char_length(name) = 4;


# 5.查询id小于3或者大于6的数据
select * from emp where id > 3 or id < 6;
select * from emp where id not between 3 and 6;

# 6.查询薪资不在20000，18000，17000范围的数据
select * from emp where salary not in(20000,18000,17000);

# 7.查询岗位描述为空的员工名与岗位名
select * from emp where post_comment = Null; # 不会报错 但是会匹配不到数据

select * from emp where post_comment is Null; # null 需要用is

where 练习

数据库之表的查询方式

一：where查询方式

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