I have a query with two nullable bit flag columns and I would like to coalesce those in result set into single flag:
COALESCE(flagA, flagB) as FlagAB
however for column values null, false the result is 48 rather than false which is rather unexpected. Playground example (also on db fiddle):
create table Flags (flagA bit null, flagB bit null);
insert into Flags (flagA, flagB) values (null, false);
select *, COALESCE(flagA, flagB) as FlagAB from Flags;
output:
| FlagA | FlagB | FlagAB |
--------------------------
| null | 0 | 48 |
What is going on and how can I fix the query so that it returns correctly coalesced flag?