SQL View to PostgreSQL View

CREATE OR REPLACE VIEW vwkbcomparesites as

select a.kbid kb_a, b.kbid kb_b, a.chr chr_a, a.start start_a, a."end" end_a, (a."end" - a.start)+1 tagsize_a, 

b.chr chr_b, b.start start_b, b."end" end_b, (b."end" - b.start)+1 tagsize_b,

    abs((a."end" + a.start)/2 - (b."end" + b.start)/2) centredistance,

case 

when a."end" <= b."end" and a.start >= b.start  

then (a."end" - a.start) 

when b."end" <= a."end" and b.start >= a.start   

then (b."end" - b.start) 

when a."end" <= b."end" and a.start <= b.start    

then (a."end" - b.start) 

when a."end" >= b."end" and a.start >= b.start

then (b."end" - a.start)  

end bpoverlap

from  dbo.kbsites a inner join dbo.kbsites b on a.chr=b.chr

inner join dbo.kbdetails kbd on a.kbid=kbd.kbid

where kbd.active='1' ;

i am getting this error , how can i fix this.