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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。因为我要做的就是在这组字段为空时更新一组字段，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是Not NULLANDsubjectColumnB, timeColumnB, dataColumnB是NULL更新字段subjectColumnB, timeColumnB, dataColumnB

等等。. .

从@ravinder 的查询我想问有这种情况：让我们说这是表的内容

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

根据上述条件，我提到了“AAA1、BBB1 和 CCC1”，NULL因此这些列将被更新。结果会是这样。

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

另一种情况是，当“AAA1，BBB1，CCC1”为“NOT NULL”时，“AAA2，BBB2，CCC2”将被更新，结果将是这样的。

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

是否可以？？由于我从其他问题和答案中读到的内容使用 CASE 和 If 仅使用 2 个参数。我试过这样的查询，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 );
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1 回答 1

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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做到这一点：

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，只需添加您的标准，如果不满足，请在您的 else 中更新回自身。

- 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。

于 2013-01-29T04:57:44.263 回答