Question

sqlserver 如何实现： select a,b from ab 当a=0时inner join c 否则inner join d

Answer 1

用case， if a = 0, select a.b from ab join c
else select a,b from ab join d

Answer 2

select a,b from ab inner join c on ... where a=0
union
select a,b from ab inner join d on ... where a<>0