sql - Using IF / ELSE to determine a SELECT INTO statement -

i'm having strange issues using if / else determine 1 or 2 select statements execute. error message i'm getting when running full statement temporary table exists, not occur if run 2 separate executions of 2 separate if statements.

here code in sql server:

if (select businessdaycount calendartbl) <= 1   begin     select * #temp1     previousmonthtbl   end else   begin     select * #temp1     currentmonthtbl   end 

it's "feature" of syntax checking in sql server. cannot "create" #temporary table twice within same batch.

this pattern need.

select * #temp1 previousmonthtbl 1=0;  if (select businessdaycount calendartbl) <= 1   begin     insert #temp1 select *     previousmonthtbl   end else   begin     insert #temp1 select *     currentmonthtbl   end 

if prefer, can express branch (in case) clause:

select * #temp1 previousmonthtbl (select businessdaycount calendartbl) <= 1 union select * currentmonthtbl isnull((select businessdaycount calendartbl),2) > 1