匿名通过本文主要向大家介绍了mysql，NULL等相关知识,希望本文的分享对您有所帮助
这篇文章主要介绍了mysql 求解求2个或以上字段为NULL的记录,需要的朋友可以参考下
核心代码
/*-------------------------------- 求2个或以上字段为NULL 的记录 t1: id, id1, id2, id3, id4, id5, id6 在t1 表中有个字段； 其中id是主键； 怎样打印其中个字段或以上为NULL 的记录id？ 另外，存储过程中怎么实现按顺序一条一条读取记录最方便？ 注：主键id 是没有顺序的，也可能是字符串的； -----------------------------------------*/ drop table if exists t1; create table t1(id int,id1 int,id2 int,id3 int,id4 int,id5 int,id6 int); insert t1 select 1,1,1,1,1,null,null union all select 2,null,null,null,1,2,3 union all select 3,1,2,3,4,5,6 union all select 4,1,2,3,4,5,null union all select 5,null,3,4,null,null,null ; delimiter $$ create procedure usp_c_null() begin declare n_c int; declare idd int; declare cur cursor for select id,case char_length(concat(ifnull(id1,'@'),ifnull(id2,'@'),ifnull(id3,'@'),ifnull(id4,'@'),ifnull(id5,'@'),ifnull(id6,'@'))) -char_length(replace(concat(ifnull(id1,'@'),ifnull(id2,'@'),ifnull(id3,'@'),ifnull(id4,'@'),ifnull(id5,'@'),ifnull(id6,'@')),'@','') ) when 6 then 6 when 5 then 5 when 4 then 4 when 3 then 3 when 2 then 2 when 1 then 1 else 0 end as c from t1; declare exit HANDLER for not found close cur ; open cur; repeat fetch cur into idd,n_c; if(n_c>=2) then select * from t1 where id=idd; end if ; until 0 end repeat; close cur; end ; $$ delimiter ; /* +------+------+------+------+------+------+------+ | id | id1 | id2 | id3 | id4 | id5 | id6 | +------+------+------+------+------+------+------+ | 1 | 1 | 1 | 1 | 1 | NULL | NULL | +------+------+------+------+------+------+------+ 1 row in set (0.10 sec) +------+------+------+------+------+------+------+ | id | id1 | id2 | id3 | id4 | id5 | id6 | +------+------+------+------+------+------+------+ | 2 | NULL | NULL | NULL | 1 | 2 | 3 | +------+------+------+------+------+------+------+ 1 row in set (0.14 sec) +------+------+------+------+------+------+------+ | id | id1 | id2 | id3 | id4 | id5 | id6 | +------+------+------+------+------+------+------+ | 5 | NULL | 3 | 4 | NULL | NULL | NULL | +------+------+------+------+------+------+------+ 1 row in set (0.17 sec) */
以上就是mysql求2个或以上字段为NULL的记录求解方法的详细内容，更多请关注微课江湖其它相关文章！