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  • SQL基本练习

    1.sql对大小写不敏感
    2.sql执行顺序select--from--where--group by--having--order by 
    3.SQL 使用单引号来环绕文本值(大部分数据库系统也接受双引号)。如果是数值,请不要使用引号。
    4.ORDER BY 语句默认按照升序对记录进行排序。
    
    
    select name from persons
    select * from persons
    select name,sex from persons
    select distinct name from persons
    
    select * from persons where city='beijing'
    select * from persons where year>1996
    
    select * from persons where firstname='thoma' and lastname='carter'
    select * from persons where firstname='thoma' or lastname='carter'
    select * from persons where (firstname='thoma' or firstname='willian') and lastname='carter'
    
    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
    
    insert into table_name values (1,2,3)
    insert into table_name (name,sex,id) values ('yuanxu',1,2)
    
    update persons set firstname='fred' where lastname='willian'
    UPDATE Person SET Address = 'Zhongshan 23', City = 'Nanjing' WHERE LastName = 'Wilson'
    
    delete from persons where name='bob'
    delete from table_name
    delete * from table_name
    
    select * from persons limit 2
    select top 2 * from persons
    select top 50 percent * from persons
    
    select * from persons where city like '%lon%'
    select * from persons where city not like '%l'
    
    select * from persons where lastname like 'C_r_er' 
    我们希望从上面的 "Persons" 表中选取居住的城市以 "A" 或 "L" 或 "N" 开头的人
    select * from persons where city like '[ALN]%'
    select * from persons where city like '[!ALN]%'
    select * from persons where city like '[^ALN]%'
    
    select * from persons where lastname in ('adams','carter')
    
    select * from persons where lastname between 'adams' and 'carter'
    select * from persons where lastname not between 'adams' and 'carter'
    
    别名
    SELECT po.OrderID, p.LastName, p.FirstName
    FROM Persons AS p, Product_Orders AS po
    WHERE p.LastName='Adams' AND p.FirstName='John'
    
    SELECT LastName AS Family, FirstName AS Name
    FROM Persons
    
    SELECT Persons.LastName, Persons.FirstName, Orders.OrderNo
    FROM Persons, Orders
    WHERE Persons.Id_P = Orders.Id_P 
    
    SELECT Persons.LastName, Persons.FirstName, Orders.OrderNo
    FROM Persons
    INNER JOIN Orders
    ON Persons.Id_P = Orders.Id_P
    ORDER BY Persons.LastName
    
    UNION 操作符用于合并两个或多个 SELECT 语句的结果集。
    请注意,UNION 内部的 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。同时,每条 SELECT 语句中的列的顺序必须相同。
    SELECT E_Name FROM Employees_China
    UNION
    SELECT E_Name FROM Employees_USA
    
    SELECT E_Name FROM Employees_China
    UNION ALL
    SELECT E_Name FROM Employees_USA
    
    备份表
    select * into persons_back from persons
    select * into persons in 'backup.mdb' from persons
    select lastname,firstname into persons_backup from persons
    select lastname,firstname into persons_backup from persons where cirt='beijing'
    
    SELECT Persons.LastName,Orders.OrderNo
    INTO Persons_Order_Backup
    FROM Persons
    INNER JOIN Orders
    ON Persons.Id_P=Orders.Id_P
    
    create database my_db
    create table persons {ip int, name varchar(255)}
    
    create index personindex on person(lastname desc)
    create index personindex on person (lastname, firstname)
    
    CREATE VIEW [Current Product List] AS
    SELECT ProductID,ProductName
    FROM Products
    WHERE Discontinued=No
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  • 原文地址:https://www.cnblogs.com/yuanninesuns/p/9942404.html
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