SQL 基础语句集锦

1、创建表

2、	create table Person
3、	(
4、	id INT,
5、	LastName varchar(255),
6、	FirstName varchar(255),
7、	Address varchar(255),
8、	City varchar(255));

2、插入

insert into Person values(1,'Adams','John','Oxford Street','London');
insert into Person values(2,'Bush','George','Fifth Avenue','New York');
insert into Person (id,lastname,firstname,address,city) values(3,'Carter','Thomas','Changan Street','Beijing');

3、查询

select Lastname from person;
select Lastname,FirstName from person;
select * from person;

4、DISTINCT

create table Orders
(
Company varchar(255),
OrderNumber varchar(255)
);

insert into orders values('IBM','3532');
insert into orders values('W3School','2356');
insert into orders values('Apple','4698');
insert into orders values('W3School','6953');

select distinct company from orders;

5、WHERE

select * from person where city='Beijing';

6、AND OR

select * from person where firstname='Thomas' and lastname='Carter';
Select * from person where firstname='Thomas' or  lastname='Carter';
select * from person where (firstname='Thomas' or Firstname='William') and lastname='Carter';

7、ORDER BY

select company ,orderNumber from orders order by company;
select company ,orderNumber from orders order by company,orderNumber;
select company ,orderNumber from Orders order by Company DESC;
select company ,orderNumber from orders order by Company DESC, OrderNumber ASC;

8、UPDATE

10、	insert into person (LastName, Address) VALUES ('Wilson', 'Champs-Elysees');
11、	update person set firstname='Fred' Where lastname='Wilson';
12、	update person set address='Zhongshan 23',City ='Nanjing' where lastname='Wilson';

9、DELETE

delete from 表名称 where 列名称=值;

# 在不删除表的情况下删除所有的行
delete from 表名称;
delete * from 表名称;

10、TOP 并非所有的数据库都支持TOP

select top 2 * from person;
select top 50 percent * from Person;

11、LIKE

SELECT * from person where city like 'N%'; --选取居住在以"N"开始的城市里的人
SELECT * from person where city like '%g'; --选举居住在以"g"结尾的城市里的人
SELECT * from person where city like '%Lon%';-- 选取居住在包含“Lon”的城市里的人
SELECT * from person where city not like '%Lon%';--选取居住在不包含“Lon”的城市里的人

SQL通配符如下

通配符

描述

%

替代一个或多个字符

_

仅替代一个字符

[charlist]

字符列表中的任何单一字符

[^charlist]

[!charlist]

不在字符列中的任何单一字符(并不是所有的数据库都支持)

 

12、IN操作符

SELECT * FROM person where LastName in ('Adams','Carter');

13、BETWEEN

SELECT * FROM person where LastName BETWEEN 'Adams' AND 'Carter';--名字介于“Adams”(包括)和“Carter”(不包括)之间的人
SELECT * FROM person where LastName NOT BETWEEN 'Adams' AND 'Carter';

14、alias(别名)

SELECT po.OrderID,p.LastName,p.FirstName From Person AS p,Product_Orders AS po WHERE p.LastName='Adams' AND p.FirstName='John';
 SELECT LastName AS Family, FirstName AS Name ROM Persons

15、JOIN

select person.lastname ,person.firstname,orders.orderNo from person ,orders where person.id =orders.id_p;
select person.lastname ,person.firstname,orders.orderNo from person inner join orders on person.id =orders.id_p order by person.lastname;
--JOIN(INNER JOIN):如果表中有至少一个匹配,则返回行
--LEFT JOIN:返回左表全部行和右表满足ON条件的行
--RIGHT JOIN:返回右表全部行和左表满足ON条件的行
--FULL JOIN:返回左右表全部的行

16、UNION

UNION操作符用于合并两个或多个SELECT语句的结果集, SELECT语句必须拥有相同数量的列,列也必须拥有相似的数据类型,并且顺序必须相同。UNION只会显示不同的值,如果允许重复的值,要使用UNION ALL。

select * from Employees_china union  select * from employees_usa;

17、SELECT into

从一个表中选取数据,然后把数据插入另一个表中

SELECT lastname,firstname into persons_backup from person where city='Beijing';
select * from persons_backup;

18、SQL约束

NOT NULL:非空

UNIQUE:每个表可以用多个UNIQUE约束,但是每个表只能有一个PRIMARY KEY约束

PRIMARY KEY:每个表都应该有一个主键,并且每个表只能有一个主键

FOREIGN KEY:

CHECK:用于限制列中值的范围

DEFAULT:向列中插入默认值,如果没有规定其他的值,那么会将默认值添加到所有的新记录

19、创建索引

create index personIndex on Person(LastName);

20、alter

alter table person add birthday date;
alter table person alter birthday year;
alter table person drop column birthday;

21、auto increment

会在新记录插入表中时生成一个唯一的数字,每种数据库的具体语法有所不同

22、VIEW

CREATE VIEW [Current product list] AS  SELECT ProductID,ProductName FROM Products WHERE Discontinued=No;

23、AVG

select AVG(id_o) from orders;
select * from orders where id_o>(select AVG(id_o) from orders);--找到大于平均值的订单

24、COUNT

SELECT COUNT(column_name) FROM table_name;--COUNT(column_name) 函数返回指定列的值的数目(NULL 不计入):
SELECT COUNT(*) FROM table_name;--COUNT(*) 函数返回表中的记录数:
SELECT COUNT(DISTINCT column_name) FROM table_name;--COUNT(DISTINCT column_name) 函数返回指定列的不同值的数目

25、MAX

select max(id_o) from orders; --查找最大值

26、MIN

select min(id_o) from orders; --查找最小值

27、SUM

select sum(id_o) from orders; --计算和

28、GROUP BY

SELECT Customer,SUM(OrderPrice) FROM Orders GROUP BY Customer;--查找每个客户的总金额

29、HAVING

SELECT Customer,SUM(OrderPrice) FROM Orders GROUP BY Customer HAVING SUM(OrderPrice)<2000;--查找订单总额少于2000的客户
SELECT Customer,SUM(OrderPrice) FROM Orders WHERE Customer='Bush' OR Customer='Adams'   GROUP BY Customer   HAVING SUM(OrderPrice)>1500;--查找客户“Bush”或“Adams”拥有超过1500的订单总金额

 

    原文作者:SQL
    原文地址: https://blog.csdn.net/luchengtao11/article/details/81150333
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