MySQL一行仅选择没有NULL值的列

编程问答 2022-08-16

问题描述

    SELECT r.id AS Id,r.slot AS Slot,rg.name AS Grade,rt.name AS Type,r.main_stat AS Main Stat,r.stat01 AS 1st Substat,r.stat02 AS 2nd Substat,r.stat03 AS 3rd Substat,r.stat04 AS 4th Substat,CASE WHEN r.isEquipted = 0 THEN 'FALSE' ELSE 'TRUE' END AS isEquipted      
    FROM runes r                                                                           
    INNER JOIN rune_grade rg                                                                  
    ON r.grade_id = rg.id                                                                  
    INNER JOIN rune_type rt                                                                   
    ON r.type_id = rt.id                                                                    
    WHERE r.id = 7;

我有这个查询，只给我一条记录。 WHERE子句中的这个“ 7”在我的代码中是可变的。 我想删除为我提供NULL值的列。 该查询返回：

ID Slot Grade Type M Stat 1st Stat 2nd Stat 3rd Stat 4th Stat

7 4 normal swift spd-24 NULL NULL NULL NULL

如果where子句等于其他id，则1st 2nd 3rd 4th Stat可以具有值。

ID Slot Grade Type M Stat 1st Stat 2nd Stat 3rd Stat 4th Stat

6 3 normal swift spd-24 atk-32 hp-355 NULL NULL

对不起，英语不好。

解决方法

使用COALESCE()过滤掉所有[X Stat]列均为NULL的行：

WHERE r.id = 7 
  AND COALESCE(r.stat01,r.stat02,r.stat03,r.stat04) IS NOT NULL
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