Re: Case in Order-by clause

Hello Daniel

Thank you for thinking with me. This indeed works!

In previous preparation I already read about the difference between the case statement and the case expression. I guess the applicability in order-by clauses is one example where these differences surface.


Kind regards, Met vriendelijke groet,



Martijn van Breden

lead software architect


Hi Martijn,

Am 03.09.2024 um 14:15 schrieb Martijn van Breden <m.vanbreden@xxxxxxxxxxxxxxxxxxxxxxxxxx>:

select REFKL, ORDAT, ORDNR
from TOVF
order by
case :SortCode
when 'A' then ' ORDAT asc '
when 'D' then ' ORDAT desc '
else ' REFKL asc '
end
limit 10;

This ORDER BY expression doesn't work - as you can only have an expression instead of a column name. So this should work:

order by
case :SortCode when 'A' then ORDAT end asc,
case :SortCode when 'D' then ORDAT end desc,
case when :SortCode not in ('A', 'D') then REFKL end asc

Lets look into it in detail, when :SortCode is set - lets assume its 'D' then the cases will evaluate into this

order by
null asc,
ordat desc,
null asc

So - as the cases, which are not true, evaluate to null, their sorting doesn't effect the result set sequence.

With a case, you can switch between 2 or more columns to sort, but you cannot switch the ascending or descending.

HTH
Daniel
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