check for values in MySQL but within a specific range - mysql

Question

I am a beginner in MySQL and i want to do a check for values but within a range, i have this:
SELECT t1.width, COUNT( t1.width )
FROM test t1
INNER JOIN (
SELECT t2.width
FROM test t2
GROUP BY width
HAVING COUNT( t2.width ) >1
)t2 ON t1.width BETWEEN (t2.width +1000) AND (t2.width -1000)
ORDER BY t1.width
So what i want to do is to check if there is two values of 'width' with a difference of +1000 or -1000.
The result is always null.
could you please tell me what is wrong with the query?

Answer 1

I don't fully understand what your data is. The way I understand is you are looking to see if two values from two columns have a specific difference, i.e the first value in the first column is 2000 and the first value in the second column is 1000, since there is a difference of 1000 you want this noted. You could use the CASE function (more detail here https://www.w3schools.com/sql/func_mysql_case.asp).
Say you have one column called width_1 which consists of different values of widths, and a second column called width_2 which also consists of different width values, all contain in a table called width_table, you could use the following:
SELECT
CASE
WHEN width_1 - width_2 = 1000 OR width_1 - width_2 = -1000 THEN TRUE
ELSE FALSE
END AS column_name
FROM width_table ;
This will produce a column whose entries are either 1 if the difference is exactly +1000 or -1000, or 0 if the difference is anything else.
If you want to check if the difference is between 1000 and -1000, then you can use the following:
SELECT
CASE
WHEN width_1 - width_2 BETWEEN -1000 AND 1000 THEN TRUE
ELSE FALSE
END AS column_name
FROM width_table ;