postgresql 如果 Column1 不为空，则按 Column1 排序，否则按 Column2 排序
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Order by Column1 if Column1 is not null, otherwise order by Column2
提问by 1252748
Is there a way to combine ORDER BYand IS NULLin sql so that I can order by a column if the column isn't null, but if it is null, order by another column?
有没有办法在 sql 中组合ORDER BY和IS NULL以便我可以在列不为空时按列排序，但如果为空，则按另一列排序？
回答by Salman A
Something like:
就像是：
ORDER BY CASE
WHEN Column1 IS NOT NULL THEN Column1
ELSE Column2
END
Same as writing:
与写作相同：
ORDER BY COALESCE(Column1, Column2)
Both should work in any sane RDBMS.
两者都应该在任何正常的 RDBMS 中工作。
回答by vearutop
Try this
试试这个
ORDER BY COALESCE(fieldA, fieldB);
回答by Nurickan
I dont have any Tables atm where I could test it, but this may work, at least it did without useable data:
我没有任何可以测试它的表格自动取款机，但这可能有效，至少它在没有可用数据的情况下做到了：
SELECT * FROM table1
LEFT JOIN table2 ON table1.id = table2.id
WHERE 1
ORDER BY IF( table2.id, table1.id, table1.name )
Also I don't know how the order would look like if table2.id is null sometimes, seems very instable.
另外我不知道如果 table2.id 有时为空，订单会是什么样子，看起来很不稳定。
回答by crassr3cords
You could try with the following:
您可以尝试以下操作：
ORDER BY ISNULL(firstField, secondField)
