Count rows with a specific condition in aggregate query
44,286
Solution 1
SELECT Country,
COUNT(*) AS Total,
COUNT(CASE WHEN Reconnect = true THEN 1 END) AS With_Reconnect
FROM PlayerSession S
LEFT JOIN Player P
ON P.id = S.player_id
GROUP BY country
Solution 2
The following will suffice
SELECT
p.country,
COUNT(*) AS total,
SUM(IF(s.reconnect=TRUE,1,0)) AS with_reconnect
FROM PlayerSession s
INNER JOIN Player p
ON p.id = s.player_id
GROUP BY p.country
I just rewrote the query. You'll always have a Player row for every PlayerSession, so changed it to be an INNER JOIN. Also the CONCAT was not needed as there will always be PlayerSession rows in this query (unless there are no sessions)
Solution 3
SELECT
country,
COUNT(CASE WHEN reconnect = TRUE THEN S.player_id ELSE NULL END) AS with_reconnect,
COUNY(*)
FROM PlayerSession S LEFT JOIN Player P ON (P.id = S.player_id)
GROUP BY country
Author by
Bart van Heukelom
Professional software developer, online games, full stack but mostly backend. Electronics tinkerer. Maker. Freelance. See LinkedIn for more details. My UUID is 96940759-b98b-4673-b573-6aa6e38272c0
Updated on July 18, 2022Comments
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Bart van Heukelom almost 2 years
I have this query to get the number of
PlayerSession
s withreconnect = TRUE
, grouped byPlayer.country
:SELECT country, COUNT(*) AS with_reconnect FROM PlayerSession S LEFT JOIN Player P ON (P.id = S.player_id) WHERE reconnect = TRUE GROUP BY country
I'd like to modify it to show not just the reconnected session count, but also the total count, something like:
SELECT country, COUNT(*) AS total, (COUNT WHERE reconnect = TRUE) AS with_reconnect FROM PlayerSession S LEFT JOIN Player P ON (P.id = S.player_id) GROUP BY country
Is this possible, and if so, what is the proper syntax?