INSERT INTO table ( column1, column2, column3 )
SELECT $column1, $column2, $column3
EXCEPT SELECT column1, column2, column3
FROM table

简单的方法将数据从T1复制到T2，避免在T2中重复

--Insert a new record
INSERT INTO dbo.Table2(NoEtu, FirstName, LastName)
SELECT t1.NoEtuDos, t1.FName, t1.LName 
FROM dbo.Table1 as t1
WHERE NOT EXISTS (SELECT (1) FROM dbo.Table2  AS t2
                    WHERE t1.FName = t2.FirstName
                        AND t1.LName = t2.LastName
                        AND t1.NoEtuDos = t2.NoEtu)

看一下MERGE命令。你可以在一条语句中执行UPDATE, INSERT和DELETE操作。

下面是一个使用MERGE的工作实现 -在更新之前检查航班是否已满，否则执行插入操作。

if exists(select 1 from INFORMATION_SCHEMA.TABLES T 
              where T.TABLE_NAME = 'Bookings') 
begin
    drop table Bookings
end
GO

create table Bookings(
  FlightID    int identity(1, 1) primary key,
  TicketsMax    int not null,
  TicketsBooked int not null
)
GO

insert  Bookings(TicketsMax, TicketsBooked) select 1, 0
insert  Bookings(TicketsMax, TicketsBooked) select 2, 2
insert  Bookings(TicketsMax, TicketsBooked) select 3, 1
GO

select * from Bookings

然后……

declare @FlightID int = 1
declare @TicketsToBook int = 2

--; This should add a new record
merge Bookings as T
using (select @FlightID as FlightID, @TicketsToBook as TicketsToBook) as S
    on  T.FlightID = S.FlightID
      and T.TicketsMax > (T.TicketsBooked + S.TicketsToBook)
  when matched then
    update set T.TicketsBooked = T.TicketsBooked + S.TicketsToBook
  when not matched then
    insert (TicketsMax, TicketsBooked) 
    values(S.TicketsToBook, S.TicketsToBook);

select * from Bookings

我最终能够插入一行，在它不存在的情况下，使用以下模型:

INSERT INTO table ( column1, column2, column3 )
(
    SELECT $column1, $column2, $column3
      WHERE NOT EXISTS (
        SELECT 1
          FROM table 
          WHERE column1 = $column1
          AND column2 = $column2
          AND column3 = $column3 
    )
)

我在:

http://www.postgresql.org/message-id/87hdow4ld1.fsf@stark.xeocode.com

我在写我的解。我的方法不支持“if”或“merge”。我的方法很简单。

INSERT INTO TableName (col1,col2)
SELECT @par1, @par2
   WHERE NOT EXISTS (SELECT col1,col2 FROM TableName
                     WHERE col1=@par1 AND col2=@par2)

例如:

INSERT INTO Members (username)
SELECT 'Cem'
   WHERE NOT EXISTS (SELECT username FROM Members
                     WHERE username='Cem')

解释:

(1) SELECT col1,col2 FROM TableName WHERE col1=@par1 AND col2=@par2 它从TableName搜索值中选择

(2)选择不存在的@par1， @par2 它接受(1)子查询中if不存在

(3)在TableName(2)中插入步骤值

解决这个问题的最佳方法是首先使数据库列UNIQUE

添加唯一键

THEN INSERT IGNORE INTO table_name，如果结果是一个重复的键或已经存在于表中，则该值不会被插入。