Simple SQL Notes

sql not case sensitive.

DML (Data Manipulation Language)

select (for querying the database)

• select the column name from the table name
  • select LastName，FirstName from Persons
    
  • select * from Persons (* indicates all columns)
    
• select distinct name from table column names
  • select Company from Orders
    
  • select distinct Company from Orders
    
• Column select names from the name of the table where the value of the column operator
  operators available
  
  • select * from Persons where City=‘Beijing’
    
• and and or more operators based on the recording condition was filtered
  
  • select * from Persons where FirstName=‘Thomas’ and LastName='Carter
    
  • select * from Persons where FirstName=‘Thomas’ or LastName=‘Carter’
    
  • select * from Persons where (FirstName=‘Thomas’ or FirstName=‘william’) and Lastname=‘Carter’
    
• order by ordering for the result set (default ascending, descending the DESC keyword)
  
  • 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（用于向表格中插入新的行）

• insert into 表名称 values (值1，值2，…)
  insert into Persons values (‘Gates’, ‘Bill’, ‘Xuanwumen 10’, ‘Beijing’)
  
• insert into table_name (列1，列2，…) values (值1，值2，…)
  insert into Persons (LastName, Address) values (‘Wilson’, ‘Champs-Elysees’)
  

update（用于修改表中的数据）

update 表名称 set 列名称 = 新值 where 列名称 = 某值

• update Person set FirstName = ‘Fred’ where LastName = ‘wilson’
  
• update Person set Address = ‘Zhongshan 23’, City = ‘Nanjing’ where LastName = ‘Wilson’
  

delete（用于删除表中的行）

delete from 表名称 where 列名称 = 值

• delete from Person where LastName = ‘wilson’
  
• 不删除表的情况下删除所有行，即表的结构、属性和索引都是完整的：
  • delete from table_name或者：
  • delete * from table_name

DDL（数据定义语言）

create database: Create a new database
alter database: modify the database
create table: Create a new table
alter table: Change database table
drop table: drop table
create index: create index
drop index: Delete Index

pending upgrade