sql-重复项

Question

I'm putting data from website (json) to sql base. In db i have these rows.

ID | PostId | Name | Message

Id is auto-increment primary key. PostId also has a unique values. Name and Message are nothing special.

When I run my script / click on the button in form / ... , the program saves all the values into database (lets say there are 25). Next time I'm going to press the button there will be added 25 more records (all duplicates), and so on...

Is there a way that the program can check through 'PostIds' if the value already exists before adding it to the db?

Thanks

Answer 1

另一种方法是使用merge语句，如果愿意，它也可以更新重复的行，并且比使用if语句更容易

Answer 2

if not exists(select * from table where PostId =@PostId)
Begin
 //add
End

Answer 3

You have many option

Simple one is that you ask Your data base about that PostId

SELECT count(PostId) FROM Table where PostId = @PostId;