Celebrate National IT Professionals Day with 3 months of free Premium Membership. Use Code ITDAY17

x
?
Solved

Subquery in Check constraint

Posted on 2001-08-29
6
Medium Priority
?
2,074 Views
Last Modified: 2008-02-26
SQL Server 7.0 is telling me that I can't do this:

CONSTRAINT my_check CHECK (ColumnName IN (SELECT SomeValue FROM ReferenceTable))

It tells me that subqueries are not allowed.  So then, how do I enforce this business rule at the database level?
0
Comment
Question by:stino
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 3
  • 2
6 Comments
 
LVL 3

Expert Comment

by:ibro
ID: 6438465
CONSTRAINT myconstraint
  FOREIGN KEY  
            REFERENCES ReferenceTable ( SomeValue)  
           
0
 
LVL 3

Expert Comment

by:ibro
ID: 6438476
sorry...i missed something

CONSTRAINT myconstraint
 FOREIGN KEY  (MyValue)
           REFERENCES ReferenceTable ( SomeValue)  
0
 
LVL 1

Author Comment

by:stino
ID: 6438596
cool, but supposed I wanted to do a filter. Eg.  CONSTRAINT myConstraint CHECK (SELECT SomeField FROM SomeTable WHERE SomeField = 'CONSTANTVALUE')

your solution basically means that I'm enforcing referential integrity on the two tables.  Which will work fine for what I'm doing now but I foresee the need to accomplish the above mentioned scenario
0
What Is Blockchain Technology?

Blockchain is a technology that underpins the success of Bitcoin and other digital currencies, but it has uses far beyond finance. Learn how blockchain works and why it is proving disruptive to other areas of IT.

 
LVL 143

Accepted Solution

by:
Guy Hengel [angelIII / a3] earned 120 total points
ID: 6439375
In that case, you MUST use triggers to enforce these rules:

CREATE TRIGGER <triggername>
ON YourTable
FOR INSERT, UPDATE
IF UPDATE(ColumnName)
  IF EXISTS ( SELECT ColumnName FROM inserted LEFT JOIN SomeTable ON SomeTable.SomeField = inserted.ColumnName
  WHERE <whatever>  
   AND SomeTable.SomeField IS NULL )
     BEGIN    
        ROLLBACK TRAN
        -- eventually RAISERROR ...
     END

Cheers
0
 
LVL 3

Expert Comment

by:ibro
ID: 6439505
agree with angel, thats the best way you can do filtering constraint.
the other way is to implement your logic in stored procedures and put all kind of checkings in there. in this case you have to forget about direct sql updates/inserts in the table from your front end application. you have to always use stored procedures for all kind of updates. this will give you good performance as well and you can implement complex business logic in sp.
0
 
LVL 1

Author Comment

by:stino
ID: 6440764
Thanks alot guys.  ibro, I'm gonna post some points for you as well because you did answer the initial question.
0

Featured Post

Does Your Cloud Backup Use Blockchain Technology?

Blockchain technology has already revolutionized finance thanks to Bitcoin. Now it's disrupting other areas, including the realm of data protection. Learn how blockchain is now being used to authenticate backup files and keep them safe from hackers.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Ever needed a SQL 2008 Database replicated/mirrored/log shipped on another server but you can't take the downtime inflicted by initial snapshot or disconnect while T-logs are restored or mirror applied? You can use SQL Server Initialize from Backup…
When trying to connect from SSMS v17.x to a SQL Server Integration Services 2016 instance or previous version, you get the error “Connecting to the Integration Services service on the computer failed with the following error: 'The specified service …
Via a live example, show how to backup a database, simulate a failure backup the tail of the database transaction log and perform the restore.
Viewers will learn how to use the INSERT statement to insert data into their tables. It will also introduce the NULL statement, to show them what happens when no value is giving for any given column.

730 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question