Mysql——查询字段是否为空

如何设置条件

• 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

• 当查询条件为 null，用指定字符替代

  select name,  isfull(gender,\'未知\') as gender  from users where email = \'xxxx\'