MS SQL 检查两个字段是否重复

Question

我正在尝试创建一个触发器，根据他们的名字和姓氏的组合检查作者是否已经存在于 table 中。从我一直在阅读的内容来看，这个触发器应该可以工作，但是当我尝试将任何新作者插入 table 时，它会给出 "Author exists in table already!" 错误，即使我插入的作者在 table.

这是触发器

USE [WebsiteDB]
GO
CREATE TRIGGER [dbo].[tr_AuthorExists] ON [dbo].[Authors]
AFTER INSERT
AS

if exists ( select * from Authors
    inner join inserted i on i.author_fname=Authors.author_fname AND i.author_lname=Authors.author_lname)
begin
    rollback
    RAISERROR ('Author exists in table already!', 16, 1);
End

这是table

CREATE TABLE [dbo].[Authors](
    [author_id] [int] IDENTITY(1,1) NOT NULL,
    [author_fname] [nvarchar](50) NOT NULL,
    [author_lname] [nvarchar](50) NOT NULL,
    [author_middle] [nvarchar](50) NULL,
CONSTRAINT [PK_Authors] PRIMARY KEY CLUSTERED 
(
    [author_id] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]

如有任何帮助，我们将不胜感激！

Answer 1

您需要代替触发器来执行此操作。这也意味着您需要在触发器内部实际执行插入。沿着这些路线。

CREATE TRIGGER [dbo].[tr_AuthorExists] ON [dbo].[Authors]
instead of insert
AS
    set nocount on;

    if exists 
    ( 
        select * from Authors a
        inner join inserted i on i.author_fname = a.author_fname AND i.author_lname = a.author_lname
    )
    begin
        rollback
        RAISERROR ('Author exists in table already!', 16, 1);
    End
    else
        insert Authors
        select i.author_fname
            , i.author_lname
            , i.author_middle
        from inserted i

MS SQL 检查两个字段是否重复

MS SQL Check for duplicate in two fields

sql-server

sql-server-2014-express