SQLite/SQLAlchemy：检查多个列的值是否为 NULL 或相同

发布于 2025-01-12 02:02:15 字数 377 浏览 0 评论 0原文

我想检查几列：对于每一列，值要么是 NULL，要么是所有记录都相同。

例如，下表中的条件成立

+------+------+------+------+
| Col1 | Col2 | Col3 | Col4 |
+------+------+------+------+
| A    | B    | NULL | NULL |
| NULL | B    | C    | NULL |
| A    | B    | C    | NULL |
+------+------+------+------+

我该如何做到这一点，最好使用一个查询？

编辑：
另一个问题是：如何对每个选定列的不同值求和

原文

I would like to check for several columns that: For each column the value is either NULL or the same for all records.

For example, the condition holds for the following table

+------+------+------+------+
| Col1 | Col2 | Col3 | Col4 |
+------+------+------+------+
| A    | B    | NULL | NULL |
| NULL | B    | C    | NULL |
| A    | B    | C    | NULL |
+------+------+------+------+

How can I do that, preferably with one query?

EDIT:
An alternative question would be: How can I sum the distinct values of each of the selected columns

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撩动你心 2025-01-19 02:02:15

您可以检查每个单独列中的不同值数量是否小于或等于 1：

SELECT COUNT(DISTINCT Col1) <= 1 ok1,
       COUNT(DISTINCT Col2) <= 1 ok2,
       COUNT(DISTINCT Col3) <= 1 ok3,
       COUNT(DISTINCT Col4) <= 1 ok4
FROM tablename;

或者，您可以获得整个表的结果：

SELECT MAX(
         COUNT(DISTINCT Col1),
         COUNT(DISTINCT Col2),
         COUNT(DISTINCT Col3),
         COUNT(DISTINCT Col4)
       ) <= 1 ok  
FROM tablename;

请参阅演示。

You can check if the distinct number of values in each individual column is less than or equal to 1:

SELECT COUNT(DISTINCT Col1) <= 1 ok1,
       COUNT(DISTINCT Col2) <= 1 ok2,
       COUNT(DISTINCT Col3) <= 1 ok3,
       COUNT(DISTINCT Col4) <= 1 ok4
FROM tablename;

Or, you can get a result for the the whole table:

SELECT MAX(
         COUNT(DISTINCT Col1),
         COUNT(DISTINCT Col2),
         COUNT(DISTINCT Col3),
         COUNT(DISTINCT Col4)
       ) <= 1 ok  
FROM tablename;

See the demo.

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