Question

How do I specify constraint on my field that allows null but if value exists it should be one of values of primary key within existing table? Take a look at the code:

  CREATE TABLE TestTable  (     RowId int IDENTITY NOT NULL PRIMARY KEY,     RowParentId int NULL, -- < how do I specify constraint that RowParentId if not NULL should be RowId (foreign key to existing table?)     RowName nvarchar(30),     RowShortName nvarchar(10) ) GO 

I want to be able to generate parent child view without limiting depth and enforcing constraint on existing parent.

Hope I was able to convey what I’m looking for.

Cheers

Answer 1

Isn’t that just a foreign key?

RowParentId int NULL references ParentTable (ParentTableIdColumn), 

if it is not null, then it must be a value from the parent table.