SQL Check Constraint that requires a not null value in a column based on the value of another column

I have a table with the following two columns

• OnSite BIT NOT NULL

• ClientId INT NULL

I want to add a constraint that requires ClientId to be NOT NULL when OnSite is true(1).

I could not find anything on the site.

Thanks

You want to enforce the implication:

(OnSite=true) => (ClientId is not null)

This can be rewritten as:

(OnSite=false) or (ClientId is not null)

Your constraint therefore becomes:

CHECK ( OnSite=0 or ClientId is not null)

StackExchange Database Administrators Q#66681, answer score: 9