如何比较同一个表中的两列？

I would like to compare two columns in the same table. I want to be able to return all rows where the two columns have the same value.

我想比较同一个表中的两列。我希望能够返回两列具有相同值的所有行。

I am looking for something like SELECT * FROM FOO WHERE C1 = C4.

我正在寻找像SELECT * FROM FOO WHERE C1 = C4这样的东西。

Therefore in the example below I would return only the first row:

因此，在下面的示例中，我将只返回第一行：

C1    || C2  || C3  || C4
--------------------------
1     || a   || b   || 1
2     || a   || b   || 4
3     || b   || d   || 2
4     || b   || d   || 2

If it matters, I am using SQLite (more specifically WebSQL).

如果重要，我使用SQLite（更具体地说是WebSQL）。

1 个解决方案

#1

SELECT * FROM FOO WHERE C1 = C4 should work. Does it not?

SELECT * FROM FOO WHERE C1 = C4应该有效。不是吗？

If not, are they the same data type and length? You may need to convert.

如果没有，它们的数据类型和长度是否相同？您可能需要转换。

I don't know about WebSql, but I've seen some db systems that refuse to match if one is a varchar(5) and the other is a varchar(10) even though they hold the same value. In those systems you have to use something like

我不知道WebSql，但是我看到一些db系统拒绝匹配，如果一个是varchar（5）而另一个是varchar（10），即使它们保持相同的值。在那些系统中你必须使用类似的东西

 Convert(varchar, 10, FieldName)

to get a match.

得到一个匹配。

#1