sql的基础用法

# sql 对大小写不敏感

# 查询表中的所有信息
select * from `Customers`;
# 查询指定字段 CustomerName,Country
select CustomerName,Country from `Customers`
# distinct 去重复 
select * distinct Country  from `Customers`
# 客户的国家数量
select COUNT(DISTINCT Country) from `Customers`
#where 语句
select * from `Customers` where Country = 'Mexico'
#= 等于  <> 不等于 > 大于 < 小于  >= 大于等于  <= 小于等于  between 在某个范围内  like 搜索某种模式  IN  为列指定多个可能的值
select * from `Customers` where `CustomerID`=1
#<>  不等于1
select * from `Customers` where CustomerID <> 1
#>
select * from `Customers` where CustomerID > 3
#<
select * from `Customers` where CustomerID < 3
#>=
select * from `Customers` where CustomerID >= 3
#<=
select * from `Customers` where CustomerID <= 3
#between and 3~5
select * from `Customers` where CustomerID between 3 and 5
#like 
select * from `Customers` where `City` like '%n%'
select * from `Customers` where `City` like '%n'
#and 
select * from `Customers` where `Country`='Germany' and City = 'Berlin'
#or 
select * from `Customers` where `Country`='Germany' or City = 'London'
#Not
select * from `Customers` where not Country = 'Germany'
#结合 and or
select * from `Customers` where Country = 'Germany' and (City='Berlin' OR City='München')
#order by
select * from `Customers` order by Country;
#order by desc 降序排列
select * from `Customers` order by Country desc;
#order by 多列
select * from `Customers` order by Country,CustomerName;
#order by 多列实例2
select * from `Customers` ORDER BY Country ASC,CustomerName DESC;
#insert into 实例 插入数据
insert into `Customers`(CustomerName,ContactName,Address,City,PostalCode,Country)
values ('Cardinal','Tom B. Erichsen','Skagen 21','Stavanger','4006','Norway')
#仅在指定的列中插入数据
insert into `Customers`(CustomerName,City,Country) values ('Cardinal','Stavanger','Norway')
#NULL 空值 如何测试NULL值 
select CustomerName,ContactName,Address from `Customers` where Address is null
#is not null
select * from `Customers` where Address is not null
#更新表中的记录 update
# update table_name  set column1 = value1,column2 = value2,.... where condition
update `Customers` set ContactName = 'Alfred Schmidt',City='Frankfurt999999' where CustomerID =1
#更新多个记录数据
update Customers set ContactName = 'Juan' where Country='Mexico'
#删除数据  delete
# delete from table_name where condition
delete from Customers where CustomerName='Alfreds Futterkiste'
#删除所有的数据
#delete from table_name
#或者
# delete * from table_name

###############################################SQL 高级##########################
#前4条数据
select * from `Customers` limit 4
#like  搜索 关键字
#  %  百分号标识零个，一个或多个字符
# _ 下划线标识单个字符
select * from `Customers` where CustomerName like 'a%' 
select * from Customers where CustomerName like '%or%'
# _ 单个字符
#选择客户名称在第二位具有r的所有客户
select * from Customers where CustomerName like '_r%'
#以a开头 至少有三个字符
select * from Customers where CustomerName like 'a_%_%'
#以a开头并且以o结尾
select * from Customers where CustomerName like 'a%o'
# 不以a开头的所有客户
select * from Customers where CustomerName not like 'a%'
# 不以bsp 开头
select * from Customers where CustomerName like '[!bsp]%'
#IN 运算符允许您在where子句中指定多个值  IN运算符是多个or条件的缩写
select * from Customers where Country in ('Germany', 'France', 'UK')
# not in 
select * from Customers where Country not in ('Germany', 'France', 'UK')
#选取来自同一国家的所有客户作为供应商：
select * from `Customers` where Country in (select Country from Suppliers)
#between and
select * from Products where Price between 10 and 20
#not betwee and
select * from Products where price not between 10 and 20
#价格在10到20之间但CategoryID不是1、2或3的所有产品
select * from Products where (Price Between 10 and 20) and not CategoryID in (1,2,3)
#时间段内的所有订单
select * from Orders WHERE OrderDate BETWEEN '#07/04/1996#' AND '#07/09/1996#'

#inner join  on  交集
select Orders.`OrderID`,`Customers`.`CustomerName`,`Orders`.`OrderDate` from `Orders`
inner join `Customers` on Orders.`CustomerID`=Customers.`CustomerID`
#inner join 关键字（内部连接） 内部链接inner join 关键字选择两个表中具有匹配值的记录
#返回所有下订单的客户
select Customers.`CustomerName`,Orders.`OrderID` from Customers
inner join `Orders`
on Customers.`CustomerID` = Orders.`CustomerID`
order by Customers.`CustomerName`


#查询出医院下面的科室
select `biz_hospital`.`name`,`biz_hospital`.`hospital_id`,`biz_hospital`.`city`,`biz_hospital`.`level`,
`biz_room`.`room_id`,`biz_room`.`name` room_name from `biz_hospital`
inner join `biz_room` on `biz_hospital`.`hospital_id` = `biz_room`.`hospital_id` and `biz_hospital`.`status` =1 and `biz_room`.`status` =1

#查询出来医院下面所有科室下面的所有医生
select `biz_hospital`.`name` hospital_name,`biz_hospital`.`city`,`biz_hospital`.`level`,`biz_room`.`room_id`,`biz_room`.`name` room_name,
`biz_doctor`.`name` doctor_name 
from ((`biz_hospital` inner join `biz_room` on `biz_hospital`.`hospital_id` = `biz_room`.`hospital_id` and `biz_hospital`.`status` =1 and `biz_room`.`status`=1 )
inner join `biz_doctor` on `biz_room`.`room_id` = `biz_doctor`.`room_id` and `biz_doctor`.`status`=1) 

#有开放科室的医院
select `biz_hospital`.`hospital_id`,`biz_hospital`.`name` hospital_name,`biz_hospital`.`city`,`biz_hospital`.`level`
,`biz_open_room`.`room_name`