Mysql 使用子查询时 where 条件筛选 时灵时不灵? - V2EX
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black11black
V2EX    MySQL

Mysql 使用子查询时 where 条件筛选 时灵时不灵?

  •  
  •   black11black 2020-03-31 16:27:35 +08:00 2732 次点击
    这是一个创建于 2026 天前的主题,其中的信息可能已经有所发展或是发生改变。

    如题,不太清楚原因。数据库版本 mariadb 10.3

    SELECT * FROM (SELECT * FROM `000001_day` WHERE `securelevel` < 2) AS subtable WHERE subtable.value >= '12.6'; 

    这是一个简单的子表查询,先筛选 securelevel < 2 的,然后在筛选 value >12.6 的,工作正常,得到如下结果

     date id value securelevel 2020-03-24 9123 12.61 1 2020-03-25 9123 12.87 1 2020-03-26 9123 13.06 1 2020-03-27 9123 13.15 1 2020-03-30 9123 12.94 1 

    但是如果我将条件改成大于等于 12.61 (正常情况下搜索结果不变,因为包含了第一列的 value ),但是搜索结果却变成

     date id value securelevel 2020-03-25 9123 12.87 1 2020-03-26 9123 13.06 1 2020-03-27 9123 13.15 1 2020-03-30 9123 12.94 1 

    第一项消失了。

    尝试了一些其他选项,等于运算都不太好使,大于小于倒是都工作正常。

    求问各位带佬这是咋回事

    black11black
        1
    black11black  
    OP
       2020-03-31 16:31:13 +08:00
    比如如果搜索

    SELECT * FROM
    (SELECT * FROM `000001_day` WHERE `securelevel` < 2) AS subtable
    WHERE subtable.value = '12.61';

    就会返回空结果,懵
    q4487979711
        2
    q4487979711  
       2020-03-31 16:35:32 +08:00
    12.6 的单引号去掉
    black11black
        3
    black11black  
    OP
       2020-03-31 16:37:57 +08:00
    @q4487979711 没用,但感觉应该是浮点数引起的问题
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