Question

https://stackoverflow.com/a/11177086/1947965

从上面的正确答案链接我想跟进另一个问题。因为我想要做的就是当这组字段为空时更新字段集，否则更新到另一组字段而不仅仅是单个列。这是另一种情况：

1。）如果subjectColumnA, timeColumnA, dataColumnA是NULL更新字段。

2。）如果subjectColumnA, timeColumnA, dataColumnA为Not NULL且subjectColumnB, timeColumnB, dataColumnB为NULL，则更新字段为subjectColumnB, timeColumnB, dataColumnB

等等。。

来自@ ravinder的查询我想问这个场景：让我们说这是表格的内容

+------+------+------+------+------+------+------+------+------+------+
| id   | AAA1 | BBB1 | CCC1 | AAA2 | BBB2 | CCC2 | AAA3 | BBB3 | CCC3 |
+------+------+------+------+------+------+------+------+------+------+
|    1 | NULL | NULL | NULL | NULL | NULL | NULL | NULL | NULL | NULL |
+------+------+------+------+------+------+------+------+------+------+

从上面的条件我提到'AAA1，BBB1和CCC1'是NULL所以这些列将会更新。结果将是这样的。

+------+------+------+------+------+------+------+------+------+------+
| id   | AAA1 | BBB1 | CCC1 | AAA2 | BBB2 | CCC2 | AAA3 | BBB3 | CCC3 |
+------+------+------+------+------+------+------+------+------+------+
|    1 |    2 |    2 |    2 | NULL | NULL | NULL | NULL | NULL | NULL |
+------+------+------+------+------+------+------+------+------+------+

另一个例子是当'AAA1，BBB1，CCC1'为'NOT NULL'时，'AAA2，BBB2和CCC2'将被更新，其结果将如下所示。

+------+------+------+------+------+------+------+------+------+------+
| id   | AAA1 | BBB1 | CCC1 | AAA2 | BBB2 | CCC2 | AAA3 | BBB3 | CCC3 |
+------+------+------+------+------+------+------+------+------+------+
|    1 |    3 |    3 |    3 | NULL | NULL | NULL | NULL | NULL | NULL |
+------+------+------+------+------+------+------+------+------+------+

有可能吗？因为我从别人那里读到的问题和答案使用CASE和If仅使用2个参数。我尝试过像这样的查询，但它失败了。

UPDATE table SET
    AAA3 = IF( AAA2 IS NOT NULL, 2, AAA3 ) AND BBB3 = IF( BBB2 IS NOT NULL, 2, BBB3 ),
    AAA2 = IF( AAA1 IS NOT NULL, 2, AAA2 ) AND BBB2 = IF( BBB1 IS NOT NULL, 2, BBB2 ),
    AAA1 = IF( AAA1 IS NULL, 1, AAA1 ) AND BBB1 = IF( AAA1 IS NULL, 1, BBB1 );

Answer 1

如果没有示例数据和所需的输出，真的很难回答这个问题，但是使用您提供的链接和上面的伪语法，您应该能够以完全相同的方式执行此操作：

UPDATE TableName SET 
subjectColumnA = ( case when subjectColumnA is null 
                        AND timeColumnA is null 
                        AND dataColumnA is null 
                    then ? 
                    else subjectColumnA end ),
timeColumnA = ( case when subjectColumnA is null 
                        AND timeColumnA is null AND 
                        dataColumnA is null 
                     then ? 
                     else timeColumnA end ),
dataColumnA = ( case when subjectColumnA is null AND 
                        timeColumnA is null AND 
                        dataColumnA is null 
                     then ? 
                     else dataColumnA end ),
subjectColumnB = ( case when subjectColumnA is not null AND 
                        timeColumnA is not null AND 
                        dataColumnA is not null AND 
                        subjectColumnB is null AND 
                        timeColumnB is null AND 
                        dataColumnB is null 
                    then ? 
                    else subjectColumnB end ),
timeColumnB = ( case when subjectColumnA is not null AND 
                        timeColumnA is not null AND 
                        dataColumnA is not null AND 
                        subjectColumnB is null AND 
                        timeColumnB is null AND 
                        dataColumnB is null 
                    then ? 
                    else timeColumnB end ),
dataColumnB = ( case when subjectColumnA is not null AND 
                        timeColumnA is not null AND 
                        dataColumnA is not null AND 
                        subjectColumnB is null AND 
                        timeColumnB is null AND dataColumnB is null 
                    then ?
                    else dataColumnB end )

真的，只需添加您的条件，如果不符合，则在您的其他地方更新回自己。

- 编辑

使用上面的查询，您仍然可以使用CASE - 工作方式与IIF相同：

UPDATE table SET
    AAA3 = CASE WHEN AAA2 IS NOT NULL THEN 2 ELSE AAA3 END,
    BBB3 = CASE WHEN BBB2 IS NOT NULL THEN 2 ELSE BBB3 END,
    AAA2 = CASE WHEN AAA1 IS NOT NULL THEN 2 ELSE AAA2 END,
    BBB2 = CASE WHEN BBB1 IS NOT NULL THEN 2 ELSE BBB2 END,
    ...

祝你好运。

更新Mysql（如果2列为null则转到下2列）

1 个答案: