Thanks SET.  I tried both your examples, the CASE WITH fails for me because I am still using FB2.5.  The other one works but the query has slowed down considerably to 3-5 minutes.  Of course this is a complex query already using a CTE and then the query itself joins a few tables and a View.

The field of interest cNameCity01 is from a View in FireBird and this is slowing down the query.  Even if I do not put the WHERE condition and I just JOIN the View the query slows down.  I have tried to replace this character field with it's ID in case strings are slow but no joy.

I had also tried to move the JOIN of the View from the main query into the CTE (as character as well as integer ID) as I just needed this one field, though the SELECT of the CTE itself with this JOIN is very fast but as a whole query it remains slow.

I have tried to add index for fields in JOINs and ORDER BYs but no difference

Any suggestions?

Thanks and regards

Bhavbhuti

 

Hi Bhavbhuti!

According to https://firebirdsql.org/refdocs/langrefupd15-case.html

this is how case is written:

CASE <expression>

   WHEN <exp1> THEN result1

   WHEN <exp2> THEN result2

   ...

   [ELSE defaultresult]

END

   

and definitely not 

CASE <expression>

   WHEN <exp1> THEN comparison

   WHEN <exp2> THEN comparison2

   ...

   [ELSE defaultcomparison]

END

If you insist on using this construct, you have to modify to something like:

WHERE 1 = CASE WHEN TRIM(vwTA.cNameCity01) = 'Balance Sheet'

THEN case when CAST(tSI.tDt AS DATE) < '2018-04-01' then 1 else 0 end

ELSE case when CAST(tSI.tDt AS DATE) BETWEEN '2018-03-01' AND '2018-03-31' then 1 else 0 END

but it is - of course - better to use things as they are intended to be used, e.g. directly in the SQL like

WHERE CAST(tSI.tDt AS DATE) < '2018-04-01' AND

      (TRIM(vwTA.cNameCity01) = 'Balance Sheet' OR

       CAST(tSI.tDt AS DATE) BETWEEN '2018-03-01' AND '2018-03-31')

2018-06-19 10:25 GMT+02:00 venussoftop@... [firebird-support] <firebird-support@yahoogroups.com>:

Hi all

I am trying to write a conditional WHERE clause but it fails.  Please suggest a correct way to write this

WHERE CASE WHEN TRIM(vwTA.cNameCity01) = 'Balance Sheet'

THEN CAST(tSI.tDt AS DATE) < '2018-04-01'

ELSE CAST(tSI.tDt AS DATE) BETWEEN '2018-03-01' AND '2018-03-31' END

vwTA and tSI are all joined into the query and the error I receive is

Message: isc_dsql_prepare failed

SQL Message : -104
Invalid token

Engine Code    : 335544569
Engine Message :
Dynamic SQL Error
SQL error code = -104
Token unknown - line 35, column 29
<

This is the < in the THEN clause

Please advise

Kind regards

Bhavbhuti

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Thanking you.

Yours Faithfully,
For Venus Software Operations
----
Mr. Bhavbhuti Nathwani
___________________________________________
Softwares for Indian Businesses at: http://www.venussoftop.com

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