我需要编写一个T-SQL存储过程来更新表中的一行。如果该行不存在,则插入它。所有这些步骤都由一个事务包装。

这是一个预订系统,所以它必须是原子和可靠的。如果事务已提交且机票已预订,则必须返回true。

我确定如何使用@@rowcount。这就是我到目前为止所写的。我走的路对吗?

-- BEGIN TRANSACTION (HOW TO DO?)
    
UPDATE Bookings
 SET TicketsBooked = TicketsBooked + @TicketsToBook
 WHERE FlightId = @Id AND TicketsMax < (TicketsBooked + @TicketsToBook)

-- Here I need to insert only if the row doesn't exists.
-- If the row exists but the condition TicketsMax is violated, I must not insert 
-- the row and return FALSE

IF @@ROWCOUNT = 0 
BEGIN

 INSERT INTO Bookings ... (omitted)
               
END

-- END TRANSACTION (HOW TO DO?)

-- Return TRUE (How to do?)

当前回答

你可以使用合并功能来实现。否则你可以:

declare @rowCount int

select @rowCount=@@RowCount

if @rowCount=0
begin
--insert....

其他回答

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

INSERT INTO [DatabaseName1].dbo.[TableName1] SELECT * FROM [DatabaseName2].dbo.[TableName2]
 WHERE [YourPK] not in (select [YourPK] from [DatabaseName1].dbo.[TableName1])

我假设每个航班都有一排座位?如果是这样:

IF EXISTS (SELECT * FROM Bookings WHERE FLightID = @Id)
BEGIN
    --UPDATE HERE
END
ELSE
BEGIN
   -- INSERT HERE
END

我认为我说的,因为你的做事方式可能会超额预订航班,因为当最多有10张票而你预订了20张票时,它会插入一个新的行。

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