MySQL >, <, and missing by group - mysql

Question

I have two tables in MySQL that I'm comparing with the following attributes:
tbl_fac : facility_id, chemical_id, criteria
10 , 25 , 50
10 , 26 , 60
10 , 27 , 60
11 , 25 , 30
11 , 27 , 31
etc...
tbl_samp: sample_id, chemical_id, result
5 , 25 , 51
5 , 26 , 61
6 , 25 , 51
6 , 26 , 61
6 , 27 , 500
etc....
These tables are joined by chemical_id (many-to-many---- ugh), and there are several thousand facility_id's, and several hundred chemical_id's for each facility_id. There are also several thousand sample_id's, each with several hundred chemical_id's for each sample_id. All-in-all, there are around 500,000 records in tbl_fac, and 1,000,000+ records in tbl_samp.
I'm trying to extract three groups of sample_id's from this dataset:
Group 1: any sample_id where tbl_samp.result > tbl_fac.criteria (i.e., result exceeds criteria)
Group 2: any sample_id where tbl_samp.result < tbl_fac.criteria, AND all tbl_fac.chemical_id's are present for that sample_id (i.e., result is less than criteria, and everything is there)
Group 3: any sample_id where tbl_samp.result < tbl_fac.criteria, BUT one or more tbl_fac.chemical_id's are missing in the sample_id (i.e., result is less than criteria, but something is missing)
Here's the Question: How do I get all three Groups efficiently in one query?
I've tried:
select *
from tbl_fac
left join tbl_samp
on tbl_fac.chemical_id = tbl_samp.chemical_id
But this only yields values that are missing for the entire dataset (not the individual samples). I have a hackish query working that uses a third table to join tbl_fac and tbl_samp, but it is so ugly I'm actually embarrassed to post it....
As always, many thanks in advance for your thoughts on this one!
Cheers,
Josh
EDIT: Ideally, I would like the sample_id and Group returned -- with just one Group per sample ID (my knowledge of the data indicates that they will always fall into one of the three categories above).

Answer 1

This answer makes the assumption that there is a unique constraint on facility_id and chemical_id in tbl_fac and a unique constraint on sample_id and chemical_id in tbl_samp. What I did was build up the query one step at a time. Whether this is efficient remains to be seen.
Group 1: any sample_id where tbl_samp.result > tbl_fac.criteria (i.e., result exceeds criteria)
SELECT tbl_samp.sample_id,
'ResultsGreaterThanCriteria' AS samplegroup
FROM tbl_fac
INNER JOIN tbl_samp
ON tbl_fac.chemical_id = tbl_samp.chemical_id
WHERE tbl_samp.result > tbl_fac.criteria
GROUP BY tbl_samp.sample_id
Group 2: any sample_id where tbl_samp.result < tbl_fac.criteria, AND all tbl_fac.chemical_id's are present for that sample_id (i.e., result is less than criteria, and everything is there)
SELECT tbl_samp.sample_id,
'ResultLessThanCriteriaAndAllChems' AS samplegroup
FROM tbl_fac
INNER JOIN tbl_samp
ON tbl_fac.chemical_id = tbl_samp.chemical_id
WHERE tbl_samp.result < tbl_fac.criteria
AND NOT EXISTS (SELECT *
FROM tbl_fac tf
LEFT JOIN tbl_samp ts
ON tf.chemical_id = ts.chemical_id
WHERE ts.chemical_id IS NULL
AND tbl_samp.sample_id = ts.sample_id)
GROUP BY tbl_samp.sample_id
Group 3: any sample_id where tbl_samp.result < tbl_fac.criteria, BUT one or more tbl_fac.chemical_id's are missing in the sample_id (i.e., result is less than criteria, but something is missing)
SELECT tbl_samp.sample_id,
'ResultsLessThanCriteriaWithMissingChems' AS samplegroup
FROM tbl_fac
INNER JOIN tbl_samp
ON tbl_fac.chemical_id = tbl_samp.chemical_id
WHERE tbl_samp.result < tbl_fac.criteria
AND EXISTS (SELECT *
FROM tbl_fac tf
LEFT JOIN tbl_samp ts
ON tf.chemical_id = ts.chemical_id
WHERE ts.chemical_id IS NULL
AND tbl_samp.sample_id = ts.sample_id)
GROUP BY tbl_samp.sample_id
And finally, you union all three queries together and get:
SELECT tbl_samp.sample_id,
'ResultsGreaterThanCriteria' AS samplegroup
FROM tbl_fac
INNER JOIN tbl_samp
ON tbl_fac.chemical_id = tbl_samp.chemical_id
WHERE tbl_samp.result > tbl_fac.criteria
GROUP BY tbl_samp.sample_id
UNION ALL
SELECT tbl_samp.sample_id,
'ResultLessThanCriteriaAndAllChems' AS samplegroup
FROM tbl_fac
INNER JOIN tbl_samp
ON tbl_fac.chemical_id = tbl_samp.chemical_id
WHERE tbl_samp.result < tbl_fac.criteria
AND NOT EXISTS (SELECT *
FROM tbl_fac tf
LEFT JOIN tbl_samp ts
ON tf.chemical_id = ts.chemical_id
WHERE ts.chemical_id IS NULL
AND tbl_samp.sample_id = ts.sample_id)
GROUP BY tbl_samp.sample_id
UNION ALL
SELECT tbl_samp.sample_id,
'ResultsLessThanCriteriaWithMissingChems' AS samplegroup
FROM tbl_fac
INNER JOIN tbl_samp
ON tbl_fac.chemical_id = tbl_samp.chemical_id
WHERE tbl_samp.result < tbl_fac.criteria
AND EXISTS (SELECT *
FROM tbl_fac tf
LEFT JOIN tbl_samp ts
ON tf.chemical_id = ts.chemical_id
WHERE ts.chemical_id IS NULL
AND tbl_samp.sample_id = ts.sample_id)
GROUP BY tbl_samp.sample_id

Answer 2

SELECT
sample_id,
IF(result = criteria, -1, /* unspecified behavior */
IF(result > criteria, 1,
IF(nb_chemicals = total_nb_chemicals, 2, 3))) AS grp
FROM (
SELECT s.result, s.sample_id, f.criteria, f.chemical_id,
COUNT(DISTINCT f.chemical_id) AS nb_chemicals
FROM tbl_fac f JOIN tbl_samp s
ON f.chemical_id = s.chemical_id
GROUP BY s.sample_id
) t
CROSS JOIN (
SELECT COUNT(DISTINCT chemical_id) AS total_nb_chemicals
FROM tbl_fac
) u
New solution:
SELECT
s.sample_id,
IF(s.result = f.criteria, -1, /* unspecified behavior */
IF(s.result > f.criteria, 1,
IF(sample_nb_chemicals = total_nb_chemicals, 2, 3))) AS grp
FROM
tbl_fac f JOIN tbl_samp s
ON f.chemical_id = s.chemical_id
JOIN (
SELECT s.sample_id,
COUNT(DISTINCT f.chemical_id) AS sample_nb_chemicals
FROM tbl_fac f JOIN tbl_samp s
ON f.chemical_id = s.chemical_id
GROUP BY s.sample_id
) u
ON s.sample_id = u.sample_id
CROSS JOIN (
SELECT COUNT(DISTINCT chemical_id) AS total_nb_chemicals
FROM tbl_fac
) v
GROUP BY sample_id, grp