MySQL中查询字段为空或者为null的方法

select * from table where  column is null;

select * from table where  column is not null;

select * from table where column ='';

CREATE TABLE `user` (
  `id` bigint(20) unsigned NOT NULL AUTO_INCREMENT COMMENT 'id 主键',
  `user_name` varchar(30) DEFAULT NULL COMMENT '用户名',
  `user_passcode` varchar(100) DEFAULT NULL COMMENT '登陆密码',
  `user_email` varchar(50) DEFAULT NULL COMMENT '邮箱',
  `user_insert_time` varchar(30) DEFAULT NULL COMMENT '用户注册时间',
  `user_update_time` varchar(30) DEFAULT NULL COMMENT '用户更新时间',
  `user_status` tinyint(4) DEFAULT '1' COMMENT '用户账号状态,1正常(默认),2禁止登陆',
  `user_version` int(10) unsigned DEFAULT '1' COMMENT '版本控制字段(默认1)',
  `user_del` tinyint(4) DEFAULT '0' COMMENT '逻辑删除字段,0正常(默认),1删除',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COMMENT='用户表';

SELECT 
    IFNULL(u.id,0), IFNULL(u.user_name,''), IFNULL(u.user_passcode,''), 
    IFNULL(u.user_email,'')
FROM `user` u
LIMIT 0,10