[SQL] Conversion from Sybase ASA

[Richard Sydney-Smith]

In sybase I can use the following syntax:   select 'T' as src,(if tbon is null or tbon < '1900/12/12' or tbon > '1900/9/30' then 'U' else 'P' endif) as pres from ftrans this returns two columns: src = '' and pres which has either the value 'U' or 'P' how would I express this in postgresql? thanks Richard