SQL Query Execution Order

We generally writes SQL in order :

SELECT → FROM → WHERE

whereas SQL actually run like in order :

FROM → WHERE → SELECT

Let that sink in

So the order you write SQL is NOT the order it executes. And once you understand this — everything changes.

The Real Order :

Step 1 — FROM / JOIN / ON

Table get joins first.

Step 2 — WHERE

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Rows are filtered.

Step 3 — GROUP BY

Rows are bucketed.

Step 4 — HAVING

Groups are filtered.

Step 5— SELECT DISTINCT

Finally — your columns are picked.

STEP 6 — ORDER BY

Results are sorted.

STEP 7—LIMIT

Only what’s needed is returned.

It’s the secret behind every fast query