Order by Column1 if Column1 is not null, otherwise order by Column2

问题

Is there a way to combine ORDER BY and IS NULL in sql so that I can order by a column if the column isn't null, but if it is null, order by another column?

回答1:

Something like:

ORDER BY CASE 
    WHEN Column1 IS NOT NULL THEN Column1
    ELSE Column2
END

Same as writing:

ORDER BY COALESCE(Column1, Column2)

Both should work in any sane RDBMS.

回答2:

Try this

  ORDER BY COALESCE(fieldA, fieldB);

回答3:

I dont have any Tables atm where I could test it, but this may work, at least it did without useable data:

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.

回答4:

You could try with the following:

ORDER BY ISNULL(firstField, secondField)

来源：https://stackoverflow.com/questions/11003413/order-by-column1-if-column1-is-not-null-otherwise-order-by-column2