Question

estado numFactura
a      1
a      2
c      3
c      4

create trigger deleteFactura 
on factura
INSTEAD OF DELETE
as
declare @estado varchar
set @estado= (select estado from deleted);
begin
    if @estado='c'
    THROW 51000, 'La factura esta cerrada, no se puede eliminar', 1
    else
    delete from factura
    where numFactura=(select numFactura from deleted)
end 
go

目标：删除带有estado ='c'的寄存器，保留带有estado='a'的寄存器

我需要它与多个值一起工作。如果我尝试删除两个值，则会出现此错误：

信息512，级别16，状态1，过程deleteFactura，第6行[批处理开始第9行]
子查询返回的值超过1。当子查询遵循=，！=，<，<=，>，> =或将子查询用作表达式时，不允许这样做。

如何使它接受多个值？

Answer 1

在编写触发器时，请始终记住，它可能正在处理多个记录。表INSERTED和DELETED中提供了要插入，删除或更新的记录。即它们似乎是表，但它们仅存在于触发器中。

create table dbo.Invoices ( Status varchar(1), InvoiceNum int )

go

create trigger DeleteInvoice on Invoices
instead of delete
as
delete from Invoices where InvoiceNum in ( select InvoiceNum from deleted ) and Status='a'

go


insert into Invoices ( Status, InvoiceNum ) values
( 'a', 1 ), ('a', 2 ), ('c', 3 ), ('c', 4 )

select * from Invoices

delete from Invoices

select * from Invoices

Answer 2

您要与已删除的集合一起加入，以仅选择要删除的行，并添加适当的WHERE子句...如下所示：

CREATE TRIGGER DeleteInvoice ON Invoices
INSTEAD OF DELETE
AS
BEGIN
    DELETE inv
      FROM Invoices inv 
           INNER JOIN deleted d ON inv.InvoiceNum = d.InvoiceNum
     WHERE inv.Status = 'a'
END

如何传递多个参数以删除触发器上的操作？

2 个答案: