SQL: Can I convert a string value of a "<" operator into an operator in a where clause? - sql

Question

I am storing an operator in a string column for two rows of a table (">", "<=")
I am joining the table with another table and want to make the where clause as dynamic as possible.
I was wondering if it's possible to convert the string value operator into an actual operator for this line of SQL code:
ABS(DATEDIFF(dd,Table2.DUE_DT,GETDATE())) > 120
VS
ABS(DATEDIFF(dd,Table2.DUE_DT,GETDATE())) <= 120
The operator will change depending on matching columns in the row. Is it possible to change the operator based of the string value containing the correct operator? If so, how can this be done?
Below are the two rows from Table1
NEFL_TYPE GRGR_ID NEFL_KEY NEFL_VALUE NEFL_COLUMN
"PDRU" "2600" "PD" "RV" ">"
"PDRU" "2600" "RV" "PD" "<="
This is the snippet of code I use:
INNER JOIN
Table1
ON
Table2.STATUS = Table1.NEFL_KEY
AND
Table1.NEFL_TYPE = 'PDRU'
WHERE
Table1.GRGR_ID = '2600'
AND
ABS(DATEDIFF(dd, Table2.DUE_DT,GETDATE())) > 120
So Table2.STATUS should determine which operator to use in the NEFL_COLUMN

Answer 1

I don't think there's an easy way to do what you want for a general case, not even with dynamic queries or client-side generated queries, as the comparison is per row and performance would be an issue with dynamic queries.
I see 2 ways to solve the particular example case, though:
a) Make 2 separate queries and do a UNION on them
SELECT...
INNER JOIN
Table1
ON
Table2.STATUS = Table1.NEFL_KEY
AND
Table1.NEFL_TYPE = 'PDRU'
WHERE
Table1.GRGR_ID = '2600'
AND
ABS(DATEDIFF(dd, Table2.DUE_DT,GETDATE())) > 120 AND Table1.NEFL_COLUMN = ">"
UNION
SELECT...
INNER JOIN
Table1
ON
Table2.STATUS = Table1.NEFL_KEY
AND
Table1.NEFL_TYPE = 'PDRU'
WHERE
Table1.GRGR_ID = '2600'
AND
ABS(DATEDIFF(dd, Table2.DUE_DT,GETDATE())) <= 120 AND Table1.NEFL_COLUMN = "<="
b) Use 2 range columns instead of an "operator" column
NEFL_TYPE GRGR_ID NEFL_KEY NEFL_VALUE NEFL_COLUMN START END
"PDRU" "2600" "PD" "RV" ">" 121 9999
"PDRU" "2600" "RV" "PD" "<=" 0 120
--------------------------------------------------------------------------
INNER JOIN
Table1
ON
Table2.STATUS = Table1.NEFL_KEY
AND
Table1.NEFL_TYPE = 'PDRU'
WHERE
Table1.GRGR_ID = '2600'
AND
ABS(DATEDIFF(dd, Table2.DUE_DT,GETDATE())) BETWEEN Table1.START AND Table1.END
But none of them are as clean or elegant as I think you would like