Skip 0 and NULL in SQL - php

Question

My previous problem and solution:
Get max and min from fields
This working OK, but i would like skip 0 and NULL in this examples.
For example:
First:
id | title
1 | aaa
2 | bbb
3 | ccc
Second:
id | first_id | one | two | three | four
1 | 1 | 3 | 0 | 4 | 6
2 | 2 | 4 | 4 | 1 | 2
3 | 3 | 1 | NULL | 3 | 4
this should show me:
id | title | min | max
1 | aaa | 3 | 6
2 | bbb | 1 | 4
3 | ccc | 1 | 4
and not:
id | title | min | max
1 | aaa | 0 | 6
2 | bbb | 1 | 4
3 | ccc | 0 | 4
In which example from my previous question is the best way to implement skip 0 and NULL?

Answer 1

Pop these into your clause
SELECT
f.id,
f.title
MIN(LEAST(greatest(coalesce(s.one,0),1), greatest(coalesce(s.two,0),1), greatest(coalesce(s.three,0),1), greatest(coalesce(s.four,0),1))) as min,
MAX(GREATEST(greatest(coalesce(s.one,0),1), greatest(coalesce(s.two,0),1), greatest(coalesce(s.three,0),1), greatest(coalesce(s.four,0),1))) as max
FROM
First f
INNER JOIN Second s
on f.id = s.first_id
GROUP BY
f.id,
f.title
You can use coalesce(fieldName, 1) to turn a null into a 1.
Again, as said in your previous question, this is HORRIBLE use of a query to force an answer. You should be changing the layout of the database.
Edit: I have nutted out the data you want, but before you look at it, be aware that if one of my colleagues wrote a script like this, he would be sacked on the spot. This is HIDEOUS and should NOT BE USED.
select
f.id,
f.title,
(select min(z.myVal) from
(
select
b.id,
b.first_id,
b.one as myVal
from
second b
where
b.one is not null
and b.one > 0
union
select
b.id,
b.first_id,
b.two as myVal
from
second b
where
b.two is not null
and b.two > 0
union
select
b.id,
b.first_id,
b.three as myVal
from
second b
where
b.three is not null
and b.three > 0
union
select
b.id,
b.first_id,
b.four as myVal
from
second b
where
b.four is not null
and b.four > 0
) z
where
f.id=z.first_id) as miniVal,
greatest(
coalesce(s.one,0),
coalesce(s.two,0),
coalesce(s.three,0),
coalesce(s.four,0)
) as maxiVal
from
first f,
second s
where
f.id=s.first_id
output Data
+------+-------+---------+---------+
| id | title | miniVal | maxiVal |
+------+-------+---------+---------+
| 1 | aaaa | 3 | 6 |
| 2 | bbbb | 1 | 4 |
| 3 | cccc | 1 | 4 |
+------+-------+---------+---------+
3 rows in set (0.00 sec)
Running this query made me throw up a little in my mouth. That's how wrong it is to write SQL like this.

Answer 2

While seemingly clunky, this solution should work:
SELECT
a.id, a.title, MIN(b.num) AS min, MAX(b.num) AS max
FROM
first a
LEFT JOIN
(
SELECT first_id, one AS num FROM second UNION ALL
SELECT first_id, two FROM second UNION ALL
SELECT first_id, three FROM second UNION ALL
SELECT first_id, four FROM second
) b ON
a.id = b.first_id AND
b.num IS NOT NULL AND
b.num > 0
GROUP BY
a.id, a.title
What this does is it actually gets each number column into its own row, but only the numbers that are not null and > 0. Before the GROUP BY, the result of the LEFT JOIN would look something like:
id | title | num
---------------------
1 | aaa | 3
1 | aaa | 4
1 | aaa | 6
2 | bbb | 1
2 | bbb | 2
2 | bbb | 4
2 | bbb | 4
3 | ccc | 1
3 | ccc | 3
3 | ccc | 4
Then by the groupings of each first (GROUP BY a.id, a.title), we can use the MIN() and MAX() aggregate functions on the num column to extract minimum and maximum values per first group:
id | title | min | max
----------------------------
1 | aaa | 3 | 6
2 | bbb | 1 | 4
3 | ccc | 1 | 4
In the case that a first_id had all four columns having NULL's or 0's, the min and max values would show up as NULL due to using a LEFT JOIN instead of an INNER JOIN as I believe this is would be a better behavior for your situation:
id | title | min | max
----------------------------
4 | ddd | NULL | NULL

Answer 3

USE:
WHERE COLUMN IS NOT NULL AND COLUMN <> 0;

Answer 4

I think you just need to nest the LEAST expressions:
LEAST(
NULLIF(one,0),
LEAST(
NULLIF(two,0),
LEAST(
NULLIF(three,0),
LEAST(
NULLIF(four,0),
null ))))
Edit I just looked it up. The LEAST function takes multiple arguments:
LEAST( NULLIF(one,0), NULLIF(two,0), NULLIF(three,0), NULLIF(four,0))
Edit 2 I see you want both min and max. Obviously you'd just change LEAST to GREATEST or MIN to MAX as needed.
This may be more straightforward or you may not have a handy least function.
SELECT
f.id, f.title,
(
SELECT MIN(NULLIF(val, 0))
FROM
(
SELECT one AS val UNION ALL
SELECT two UNION ALL
SELECT three UNION ALL
SELECT four
) AS vals
)
) as minval
FROM First f INNER JOIN Second s on f.id = s.first_id
You haven't specified if it's possible for all four columns to be null/0. We may need to tweak for that case.

Answer 5

You can use IFNULL():
WHERE IFNULL(fieldname, 0) != 0