I'm trying to add an expression for new column contains ok or null according to condition
here is my condition
if (tarih between '31.07.2016' and '31.08.2016', 'ok', 'null') but it didn't work.
*tarih refers column name contains dates
how can I make it
if(tarih>=date('31.07.2016' ) and tarih <=date('31.08.2016'),'ok','null')
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