How to create a before insert trigger with message

[ozchadl]

I am trying to create a before insert trigger for a table called "bookorder"

Table - "bookorder"
'order_id' contains numbers
'book' contains numbers
'description' contains text

The trigger is for when there is a duplicate of order_id and book.
If duplicate of both order_id and book then error message says "Error Duplicate order_id X Book Y"
eg the error message would say "Error Duplicate Order_id 1 Book 2"

If no error then message says "Record added"


Thanks for you help

[Dormilich]

wouldn’t a simple test before the db update suffice (i.e. try a select, if that returns something, don’t do the insert)

[ozchadl]

I want it done by a create trigger before event.
It is so that when new data is entered you get the error message if there is a duplicate, and a message saying that the data has been added.

This is for a mysql database.

Thanks for your help

[Dormilich]

I’m not sure, if a trigger can do that. though I’m not a SQL expert.

[ozchadl]

@ozchadl
I have been told that a trigger can do thant.

Thanks for your help