SQL Add Months to a Date
Months don't have a fixed day count, so this needs INTERVAL, not plain integer addition.
What & Why
Unlike adding days, adding months can't be done with a plain integer — date_column + 3 always means 3 days, never 3 months. Adding months requires INTERVAL '3 months', letting Postgres handle the calendar math (different month lengths, leap years) correctly.
See How It Works
BUSINESS QUESTION
Marketing wants a one-month review date for every campaign.
| 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,
start_date,
(start_date + INTERVAL '1 month')::date AS review_date
FROM marketing.campaigns
ORDER BY start_date, name;RESULT — exact output from the displayed Queryflo rows
| name | start_date | review_date |
|---|---|---|
| Spring Launch | 2024-01-15 | 2024-02-15 |
| Retention Webinar | 2024-02-10 | 2024-03-10 |
| Finance Retargeting | 2024-03-12 | 2024-04-12 |
| Enterprise Search | 2024-04-01 | 2024-05-01 |
The review date moves each campaign start by one calendar month.
Now You Try
Practice this concept
Marketing wants a one-calendar-month review date for every campaign.
Available schema
marketingPrefix tables with marketing.table_name.
namestart_datereview_datemarketing.campaigns| Column | Type |
|---|---|
| id | integer |
| name | text |
| channel | text |
| spend | numeric |
| start_date | date |
| end_date | date |
| status | text |
| target_segment | text |
| legacy_id | text |
query.sql
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