有5種方法進行查詢：

isnull()select * from users where email = 'xxxx' and isnull(deletedAt)

is nullselect * from users where email = 'xxxx' and deletedAt is null

is not nullselect * from users where email = 'xxxx' and deletedAt is not null

!isnull()select * from users where email = 'xxxx' and !isnull(deletedAt)

select * from users where email = 'xxxx' and not isnull(deletedAt)

isfull

當(dāng)查詢條件為 null，用指定字符替代select name, isfull(gender,'未知') as gender from users where email = 'xxxx'