在联表 join 时 使用 case when 按不同的条件关联不同的行

 

SELECT

OrderID,

Quantity,

CASE

WHEN Quantity > 30 THEN 'The quantity is greater than 30'

WHEN Quantity = 30 THEN 'The quantity is 30'

ELSE 'The quantity is under 30'

END AS QuantityStatus

FROM OrderDetails;

 

 

select

1

from table_a a

left jion

table_b b 

on a.f0=b.f0

and (

case when a.fb1="scene" then a.fb2=b.fb2

else 1

end 

)