SQL Subtraction

The - operator subtracts one numeric value from another — order matters, unlike addition.

What & Why

Plain - subtracts the right-hand value from the left-hand one. Unlike addition, order genuinely matters here — a - b and b - a give opposite-signed results.

See How It Works

BUSINESS QUESTION

Marketing wants unopened-recipient counts for each email send.

id	campaign_id	sent_at	recipients	opens	clicks	unsubscribes	bounces
201	1	2024-01-20 15:00:00+00	1200	540	180	9	24
202	2	2024-02-15 16:30:00+00	800	420	96	5	12
203	3	2024-03-18 13:00:00+00	1500	610	225	14	31
204	4	2024-04-08 14:00:00+00	0	0	0	0	0

EXAMPLE QUERY

SELECT
  id AS send_id,
  recipients - opens AS unopened_recipients
FROM marketing.email_sends
ORDER BY send_id;

RESULT — exact output from the displayed Queryflo rows

send_id	unopened_recipients
201	660
202	380
203	890
204	0

Recipients minus opens yields the displayed unopened counts.

Now You Try

Practice this concept

Marketing wants unopened-recipient counts for each email send.

Available schema

marketing

Prefix tables with marketing.table_name.

send_idunopened_recipients

marketing.email_sends

Column	Type
id	integer
campaign_id	integer
sent_at	timestamp with time zone
recipients	integer
opens	integer
clicks	integer
unsubscribes	integer
bounces	integer
legacy_send_group	text

query.sql

Intermediate business practice