sql server - SQL condition in join statement -


i have use conditional statement in join (sql server)

select * inner join b on a.id = b.id

if b.id null or b.id = '' should a.id2 = b.id2 instead of a.id = b.id

is correct if this:

   select * inner join b on      (b.id not null , b.id <> '' , a.id = b.id) or     ((b.id null or b.id = '') , a.id2 = b.id2)

i think not best way solve problem, useful, simple:

select * inner join b  on a.id = b.id union  select * inner join b  on a.id2 = b.id2  b.id null or b.id = ''

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