Question

So here is my very long SQL query.

Basically, I’ve got 2 school levels, JC1 & JC2 and I am counting the fields as you see below for each level for the current date and the previous date.

This is my original subquery for today, and I use another sub query with a different date.

SELECT
level,
COUNT(studentid) AS total,
SUM(leader1 <> '' OR leader2 <> '') AS leaders,
SUM(scholarship <> '') AS scholarship,
SUM(pegasus <> '') as pegasus
FROM `laterec-students` 
WHERE latetime > '2012-05-25 00:00:00' 
GROUP BY level;

It will return

level | total | leaders | scholarship |pegasus
  JC1 |  28   |    7    |      0      |   2
  JC2 |  14   |    6    |      0      |   3

Now for some dates, I may not have both JC1 & JC2 being returned. (Eg. As above 2012-05-25 I got both JC1 & JC2, for the day before, I only got JC2 because there is no JC1 data)

So this is why I did not use JOINs to help me, or maybe because I don’t really know how to use JOINs properly.

For my SQL query below,

The subqueries return this (example for subquery tjc1)

total | leaders | scholarship |pegasus
 28   |    7    |      0      |   2


SELECT

SUM(tjc1.total) AS JC1total,
SUM(yjc1.ytotal) AS JC1ytotal,
SUM(tjc1.leaders) AS JC1leaders,
SUM(yjc1.yleaders) AS JC1yleaders,
SUM(tjc1.scholarship) AS JC1scholarship,
SUM(yjc1.yscholarship) AS JC1yscholarship,
SUM(tjc1.pegasus) AS JC1pegasus,
SUM(yjc1.ypegasus) AS JC1ypegasus,

SUM(tjc2.total) AS JC2total,
SUM(yjc2.ytotal) AS JC2ytotal,
SUM(tjc2.leaders) AS JC2leaders,
SUM(yjc2.yleaders) AS JC2yleaders,
SUM(tjc2.scholarship) AS JC2scholarship,
SUM(yjc2.yscholarship) AS JC2yscholarship,
SUM(tjc2.pegasus) AS JC2pegasus,
SUM(yjc2.ypegasus) AS JC2ypegasus

FROM

(
SELECT
COUNT(studentid) AS total,
SUM(leader1 <> '' OR leader2 <> '') AS leaders,
SUM(scholarship <> '') AS scholarship,
SUM(pegasus <> '') as pegasus
FROM `laterec-students` 
WHERE latetime > '2012-05-25 00:00:00' 
AND level = 'JC1'
) tjc1,
(
SELECT
COUNT(studentid) AS ytotal,
SUM(leader1<>'' or leader2<>'') AS yleaders,
SUM(scholarship<>'') AS yscholarship,
SUM(pegasus<>'') as ypegasus
FROM `laterec-students` 
WHERE latetime BETWEEN '2012-05-24 00:00:00' AND '2012-05-24 23:59:59'
AND level = 'JC1'
) yjc1,
(
SELECT
COUNT(studentid) AS total,
SUM(leader1 <> '' OR leader2 <> '') AS leaders,
SUM(scholarship <> '') AS scholarship,
SUM(pegasus <> '') as pegasus
FROM `laterec-students` 
WHERE latetime > '2012-05-25 00:00:00' 
AND level = 'JC2'
) tjc2,
(
SELECT
COUNT(studentid) AS ytotal,
SUM(leader1<>'' or leader2<>'') AS yleaders,
SUM(scholarship<>'') AS yscholarship,
SUM(pegasus<>'') as ypegasus
FROM `laterec-students` 
WHERE latetime BETWEEN '2012-05-24 00:00:00' AND '2012-05-24 23:59:59'
AND level = 'JC2'
) yjc2

So if you think you can find a way to help me shorten my query, make it more efficient, etc. I’m forever grateful and will be able to learn something along the way. Thanks!

Answer 1

Try this:

select the_type, 
       level, 
       sum(total), 
       sum(leaders), 
       sum(scholarship), 
       sum(pegasus)

FROM
(
  (
  SELECT 
  't' the_type, 
  level,
  COUNT(studentid) AS total,
    SUM(leader1 <> '' OR leader2 <> '') AS leaders,
    SUM(scholarship <> '') AS scholarship,
    SUM(pegasus <> '') as pegasus
   FROM `laterec-students` 
  WHERE latetime > '2012-05-25 00:00:00' 
  AND level in('JC1', 'JC2')
  GROUP BY the_type, level
  ) 
UNION ALL
  (
  SELECT
   'y' the_type,
    level,
    COUNT(studentid) AS ytotal,
    SUM(leader1<>'' or leader2<>'') AS yleaders,
    SUM(scholarship<>'') AS yscholarship,
    SUM(pegasus<>'') as ypegasus
   FROM `laterec-students` 
  WHERE latetime BETWEEN '2012-05-24 00:00:00' AND '2012-05-24 23:59:59'
  AND level in('JC1', 'JC2')
  GROUP BY the_type, level
  )
) AS the_union
GROUP BY the_type, level;

An alternate way might be this:

SELECT
date(latetime) the_date,
level,
COUNT(studentid) AS total,
SUM(leader1<>'' or leader2<>'') AS leaders,
SUM(scholarship<>'') AS scholarship,
SUM(pegasus<>'') as pegasus
FROM `laterec-students` 
WHERE latetime between '2012-05-24 00:00:00' AND '2012-05-25 23:59:59'
AND level in('JC1', 'JC2')
group by the_date, level;