SQL Operator Precedence
AND binds tighter than OR — mixing them without parentheses can silently produce the wrong rows.
What & Why
When AND and OR appear in the same condition, Postgres evaluates AND first — exactly like multiplication binds tighter than addition in arithmetic. Without parentheses, the query might not mean what it looks like it means.
See How It Works
| id | name | channel | spend | start_date | end_date | status | target_segment |
|---|---|---|---|---|---|---|---|
| 1 | Spring Launch | google_ads | 55000.00 | 2024-01-15 | 2024-03-31 | active | smb |
| 2 | Retention Webinar | 45000.00 | 2024-02-10 | 2024-04-15 | active | enterprise | |
| 3 | Finance Retargeting | 50000.00 | 2024-03-12 | 2024-05-31 | active | enterprise | |
| 4 | Enterprise Search | google_ads | 60000.00 | 2024-04-01 | 2024-06-30 | active | enterprise |
EXAMPLE QUERY
SELECT name FROM marketing.campaigns
WHERE channel = 'linkedin' OR channel = 'email' AND spend > 55000;ACTUAL RESULT — AND is evaluated first
| name |
|---|
| Finance Retargeting |
SQL evaluates `channel = 'linkedin' OR (channel = 'email' AND spend > 55000)`, so Finance Retargeting survives. The mistaken grouping `(linkedin OR email) AND spend > 55000` would return no rows.
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