SQL：我可以将“ <”运算符的字符串值转换为where子句中的运算符吗？

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