Re: Suggested ways to use an exceptions table

Just spitballing, but let's it would be something like this:

WHERE (DATA.COLA, DATA.COLB, DATA.COLC, DATA.COLD) NOT IN
  (SELECT EXCP.COLA, IFNULL(EXCP.COLB, DATA.COLB),
    IFNULL(EXCP.COLC, DATA.COLC), IFNULL(EXCP.COLD, DATA.COLD) FROM EXCP)

Honestly, I don't know if this will work like you want or if it's even syntactically correct, but it seems like a start.  Basically you want matches, and you want NULL to match anything, so just substitute the original value when the exception column is NULL.



On 7/17/2019 2:50 PM, Rob Berendt wrote:

Suppose you have a table with multiple columns. Among these columns are ColA, ColB, ColC, ColD.
And you want a flexible way to omit certain rows from this table appearing on a report based on an exceptions table.
This exceptions table has four columns ColA, ColB, ColC, ColD
So if a row from the table matches those columns in the exception table do not display that row.

Now let's complicate it up a bit.

ColA will always have a value in the exceptions table. However some of the other columns may be null.

If ColD is null then omit rows where the other three match.
If ColD and ColC are null then omit rows where the other two match.
If ColD, ColC and ColB are null then omit all rows where ColA matches.
Unless it doesn't complicate items too much then let's forget about where ColD is not null but ColC is.

How would you code that in a SQL Procedure? I take it that a procedure would be necessary as it is probably too much to ask for in a basic select statement.

Rob Berendt
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