Question

Let’s suppose I have three different select statements, like this

SELECT 'Final', ID FROM Stage WHERE stageCompleted = 1;
SELECT 'Active', ID FROM Stage WHERE StartDate < NOW();
SELECT 'Inactive', ID FROM Stage;

What I would like is some way of combining these such that it displays one table that

• returns the string 'Final' and the ID of the row for all of the rows matched by the first query
• returns the string 'Active' and the ID of the row for all of the rows matched by the second query but not by the first
• and returns the string 'Inactive' and the ID of all the remaining rows.

I looked into all sorts of joins, but they don’t seem to really fit the problem I’m trying to solve. How can I combine three select queries in SQL, where each one excludes the results from the previous ones?

Answer 1

Use a case statement

SELECT
   CASE WHEN stageCompleted = 1 THEN 'Final'
        WHEN StartDate < NOW() THEN 'Active'
        ELSE 'Inactive'
   END,
   ID
FROM Stage