EXPLAIN EXTENDED

From Stack Overflow:

I have three checkboxes in my application.

If the user ticks a combination of the boxes, I want to return matches for the boxes ticked, and in the case no box is checked I just want to return everything.

Can I do this with a single SQL query?

Assuming MySQL.

The principle is simple: we need to enable filtering only if there is some data to filter. If there are no data, we should return all values.

This is best achieved by using two mutually exclusive SELECT statements with a UNION ALL.

Let's create a sample table and try to construct the query:
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