How many pairs does id

Q: How many pairs does id < id produce?

The query finds all pairs of employees in the same department. e1.id < e2.id prevents duplicates (Alice-Bob and Bob-Alice would otherwise both appear) and prevents self-pairs (Alice-Alice). In Eng there is one pair: (Alice, Bob). Carol is alone in HR and has no partner. Result: 1 row.

Question

How many pairs does id < id produce?

Accepted Answer

The query finds all pairs of employees in the same department. e1.id < e2.id prevents duplicates (Alice-Bob and Bob-Alice would otherwise both appear) and prevents self-pairs (Alice-Alice). In Eng there is one pair: (Alice, Bob). Carol is alone in HR and has no partner. Result: 1 row.