Subject Re: canOpen firing twice for DMD's query object + unexpected =/== From Gaetano <gaetanodd@hotmail.com> Date Sat, 19 Sep 2020 06:26:56 +1000 Newsgroups dbase.getting-started Hi Mervyn, I guess now I know why the pro's use == where I couldn't see a reason for it. Thanks for looking it up! Cheers, Gaetano. On 18/09/2020 18:34, Mervyn Bick wrote: > On 2020/09/17 03:07, Gaetano wrote: > >> In the following code, if I change the "==" operator to "=" in the DO >> CASE block, the first DO CASE clause evaluates to true (i.e. the code >> sees _app.varSQL as being an empty string) and cSQL doesn't get >> updated as I expected it to in the second CASE clause. >> >> I believe that the clause should not evaluate to true because >> _app.cVarSQL is set to "getMissDaysDetails" and doesn't have any >> trailing/inbetween/leading spaces. Any idea why the single "=" is not >> working in that context? >> > > This is a known "gotcha". :-) > > With EXACT set OFF (the default and recommended setting) the = symbol is > equivalent to "begins with". > > According to the help file entry for = all strings begin with an empty > string so ""=_app.cVarSQL will always return true.  It recommends > testing for  _app.cVarSQL="" > > The alternative is to use the == exactly equals symbol as you have done > or case empty(_app.cVarSQL) > > Mervyn. >