A contrived example: Say we have two types of tools: hammers and wrenches. We have a list of work orders, and we want to track what tool was used for the ...

Constraint is used on a single table whereas Trigger is used on multiple tables. For every table creation, we need to use constraints but sometimes we need to use triggers for our complex logic.

-- Constraints can be at column level or table level. -- They are used to specify rules for the data in a table by limiting the type of data that can go into a table. A primary key is used to ensure ...

To find out more information on a table, use the FEEDBACK option or the CONTENTS statement in the DATASETS procedure. The DESCRIBE VIEW statement writes a view definition to the SAS log. If you use a ...

Abstract: Reifying a constraint c consists in associating a Boolean variable b with c such that c is satisfied if and only if b is true, which can be denoted by c^{reif}: c ;=> b.Reification is useful ...

In my system, a picture can be associated with a user or a news article, but not both. Thus, I have a table with 2 foreign keys where exactly one of them is valid. I did this like so:CREATE TABLE ...