SQL Subtract Days from a Date
The mirror of adding days — a plain minus sign, useful for computing 'look-back' dates.
What & Why
date_column - n subtracts n days. This is exactly the mechanism behind "filter to the last 30 days" style queries, covered explicitly a few lessons ahead.
See How It Works
BUSINESS QUESTION
Marketing wants the seven-day preparation date before each campaign begins.
| 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
id AS campaign_id,
start_date,
start_date - INTERVAL '7 days' AS preparation_date
FROM marketing.campaigns
ORDER BY campaign_id;RESULT — exact output from the displayed Queryflo rows
| campaign_id | start_date | preparation_date |
|---|---|---|
| 1 | 2024-01-15 | 2024-01-08 00:00:00 |
| 2 | 2024-02-10 | 2024-02-03 00:00:00 |
| 3 | 2024-03-12 | 2024-03-05 00:00:00 |
| 4 | 2024-04-01 | 2024-03-25 00:00:00 |
Each preparation timestamp is seven days before campaign start.
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