I think the logic is too complicated for a CHECK constraint, and I haven't managed to get a user-defined function to work it that context so it may not be possible that way.

i need some help with a SQL alter command. i am trying to add a field to my table, but when i do the field is filled with null in any existing rows. how can i just make it fill blank like the value ...

TLDR; I would like to get a warning on changing/adding a foreign key for Postgresql that it locks the table and if the table is large, it could be locked for some time. When adding or changing a ...

Abstract: XML had already became the de facto standard of data exchange on Internet, many people had carried out a correlative study on the exchange between XML document and data with other forms, ...