T-SQL插入触发器在多个表上插入，更新if条件

Question

I'm having a few issues trying to resolve an SQL Trigger to automatically set a user to blocked & create the block record including date in another table, if their Due date is equal to a set date.

The issue is that when the trigger is set off by an insert, the print statements are executed and the insert occurs, but the insert into the table does not, or the update statement ? Can anyone explain why ?

Note: Both the insert and the Update statement are fine when executed by themselves.

ACCOUNT TABLE

CREATE TABLE [dbo].[Account](
[AccountNo] [int] IDENTITY(1,1) NOT NULL,
[CustomerNo] [int] NOT NULL,
[PaymentNo] [int] NULL,
[CreditNo] [int] NULL,
[BlockID] [dbo].[number] NULL,
[Balence] [dbo].[currency] NOT NULL,
[AmountDue] [dbo].[currency] NOT NULL,
[DueDate] [dbo].[dates] NULL,
[AutherisedBy] [nvarchar](50) NOT NULL,
[DateCreated] [date] NOT NULL,

BLOCKEDUSER TABLE

CREATE TABLE [dbo].[BlockedUsers](
[BlockID] [int] IDENTITY(1,1) NOT NULL,
[DateEnforced] [dbo].[dates] NOT NULL,
[Blocked] [dbo].[switch] NOT NULL,

TRIGGER

ALTER TRIGGER [dbo].[Add_Blocked_User]
ON [dbo].[Account]
FOR INSERT
AS  
BEGIN
SET NOCOUNT ON;

Declare @ID int
Select @ID = [AccountNo] from inserted  
If(Select [DueDate] from inserted) = '2011-01-01'

INSERT INTO dbo.BlockedUsers(DateEnforced,Blocked)
VALUES (GETDATE(),1)
PRINT 'New Block Date Added'

UPDATE Account 
Set BlockID = IDENT_CURRENT('BlockID')
where @ID = @ID
PRINT 'Account Blocked'

END

GO

Fully Working Example : Completed using Help Below.

ALTER TRIGGER [dbo].[Add_Blocked_User]
ON [dbo].[Account]
AFTER INSERT
AS 
BEGIN

SET NOCOUNT ON;

Declare @ID int
Select @ID = [AccountNo] from inserted  
 If(Select [DueDate] from inserted)Not Between (select CONVERT(date, getdate() - 30)) And (select CONVERT(date, getdate()))
Begin
    INSERT INTO dbo.BlockedUsers(DateEnforced,Blocked)
    VALUES (GETDATE(),1)
    PRINT 'New Block Date Added'

    UPDATE Account 
    Set BlockID = (Select Max(BlockID) From BlockedUsers)
    where [AccountNo] = (Select [AccountNo] from inserted)  
    PRINT 'Account Blocked'
 End

 END

GO

Answer 1

The IF statement in Transact-SQL expects a single statement after the condition:

IF condition
  statement;

If you want to perform more than one statement in the same branch, you must enclose them in the BEGIN / END "brackets":

IF condition
BEGIN
  statement;
  statement;
  ...
END;

In your trigger, only the INSERT statement executes depending on the result of the (Select [DueDate] from inserted) = '2011-01-01' condition. As for both PRINTs and the UPDATE, they execute unconditionally, ie after every insert into Account . So, you probably need to add BEGIN and END around INSERT, UPDATE and both PRINTs:

...
If(Select [DueDate] from inserted) = '2011-01-01'

INSERT INTO dbo.BlockedUsers(DateEnforced,Blocked)
VALUES (GETDATE(),1);
PRINT 'New Block Date Added';

UPDATE Account 
Set BlockID = IDENT_CURRENT('BlockID')
where @ID = @ID;
PRINT 'Account Blocked';
;
...

Answer 2

You did

FOR INSERT

You want to use

AFTER INSERT, UPDATE

FOR INSERT tells Sql Server that your trigger will entirely replace the normal insert operation. AFTER INSERT tells Sql Server to go ahead and insert the row, and then execute this code as a post-processing step.