mysql查詢最高最低，mysql字段空值在前端怎么檢驗(yàn)？
有5種方法進(jìn)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'
