Mysql——查詢字段是否為空

如何設置條件

• isnull()

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

• is null

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

• is not null

  select * 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'