Prevention of mutiple sql sum queries possible?
I would like to prevent this:
开发者_如何学编程 $florissql = "SELECT SUM(hours) FROM logs WHERE executors LIKE '%floris%'";
$rosasql = "SELECT SUM(hours) FROM logs WHERE executors LIKE '%rosa%'";
$lottesql = "SELECT SUM(hours) FROM logs WHERE executors LIKE '%lotte%'";
Is it possible to do this in just one query?
Try this maybe?
SELECT SUM(hours) AS Hours, 'floris' AS Executor FROM logs WHERE executors LIKE '%floris%'
UNION ALL
SELECT SUM(hours) AS Hours, 'rosa' AS Executor FROM logs WHERE executors LIKE '%rosa%'
UNION ALL
SELECT SUM(hours) AS Hours, 'lotte' AS Executor FROM logs WHERE executors LIKE '%lotte%'
That'll result in:
Hours | Executor
----------------
123 | floris
456 | rosa
789 | lotte
This question shows you how to use GROUP BY
with LIKE
... then you can do something like this :
SELECT
CASE
WHEN executors LIKE '%floris%' THEN 'floris'
WHEN executors LIKE '%rosa%' THEN 'rosa'
WHEN executors LIKE '%lotte%' THEN 'lotte'
END AS exec
, SUM(hours) AS hrs
FROM logs
GROUP BY
CASE
WHEN executors LIKE '%floris%' THEN 'floris'
WHEN executors LIKE '%rosa%' THEN 'rosa'
WHEN executors LIKE '%lotte%' THEN 'lotte'
END
Then you can match the sum of hours with exec on the different rows.
That question I linked to shows you more advanced methods to in case you need to do more of those...
If results per executor are required, the following should suffice:
SELECT executors, SUM(hours)
FROM logs
WHERE executors LIKE '%floris%'
OR executors LIKE '%rosa%'
OR executors LIKE '%lotte%'
GROUP BY executors
SELECT
sum(IF(executors LIKE '%floris%',hours,0)) as 'floris',
sum(IF(executors LIKE '%rosa%',hours,0)) as 'rosa',
sum(IF(executors LIKE '%lotte%',hours,0)) as 'lotte'
FROM logs;
But, you know, usage %
at first position could kill you DB performance. Because in that case indexes will not using. Try to avoid that kind of requests.
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