Filtering Cheat Sheet

You now know every WHERE operator family. This page puts them side by side so you can pick the right one quickly — and shows how they combine in one real query.

Definition recap

A WHERE condition is built as expression + operator + expression, can be combined with AND / OR / NOT, and keeps only rows for which the final result is TRUE. WHERE comes after FROM and filters rows before grouping.

Cheat sheet

Which operator should I use?

Example — several operators together

"Indian players from MI, RCB or CSK with 300 to 800 runs, whose name contains an 'h'":

SELECT name, team, runs
FROM players
WHERE country = 'India'
  AND team IN ('MI', 'RCB', 'CSK')
  AND runs BETWEEN 300 AND 800
  AND name LIKE '%h%';

How it works: FROM loads 6 rows → each row must pass all four tests (AND) → Buttler and Warner fail the country test, Bumrah fails BETWEEN (20 runs) → SELECT shows three columns.

Execution order reminder

FROM → WHERE → GROUP BY → HAVING → SELECT → ORDER BY

WHERE runs early, so it reduces rows before any grouping, aggregation or sorting happens — which is also why filtering in WHERE is efficient.

Common mistakes (all chapter)

• ❌ Text without single quotes. ✅ 'India'
• ❌ = NULL. ✅ IS NULL
• ❌ Mixing AND/OR without brackets. ✅ (A OR B) AND C
• ❌ BETWEEN high AND low. ✅ low first
• ❌ NOT IN on a subquery that may contain NULL. ✅ filter NULLs or use NOT EXISTS
• ❌ = with wildcards. ✅ LIKE

Interview tip

Q: Rewrite WHERE team = 'MI' OR team = 'CSK' OR team = 'RR' more cleanly. A: WHERE team IN ('MI', 'CSK', 'RR') — same result, shorter, and no precedence trap if you later add an AND.