SQL与UNION一起使用ORDER BY不能正确地对数字排序（例如8之前的10）

Question

I've tried looking for the answer, and read many threads on this site, but still can't find the answer I'm looking for.

I am trying to sort a series of numbers that are real look-ups and also one * which isn't, I can sort fine when I don't need to add the fake * but not after.

I have tried

SELECT DISTINCT MasterTable.ClassName, MasterTable.ClassYear
FROM MasterTable
UNION ALL
SELECT DISTINCT "*" As [ClassName], "1" As [ClassYear]
FROM MasterTable
ORDER BY MasterTable.ClassYear;

And

SELECT DISTINCT MasterTable.ClassName, MasterTable.ClassYear
FROM (
   SELECT DISTINCT MasterTable.ClassName, MasterTable.ClassYear FROM MasterTable
   UNION
   SELECT DISTINCT "*" As [ClassName], "1" As [ClassYear] FROM MasterTable
)
ORDER BY MasterTable.ClassYear;

But both return the ClassYear as 1, 10, 12, 8... rather than 1, 8, 10, 12....

Any help would be much appreciated, Thanks :)

Answer 1

MasterTable.ClassYear is varchar so it will sort as a string.

You'll have to convert it in the query or fix the column type.

For the 2nd clause, you also need only:

SELECT "*" As [ClassName], "1" As [ClassYear] --No FROM MasterTable

However, you can "cheat" and do this. Here 1 will be int and will force a conversion to int from the 1st clause because

SELECT "*" As [ClassName], 1 As [ClassYear]  --force int. And fixed on edit
UNION ALL
SELECT DISTINCT MasterTable.ClassName, MasterTable.ClassYear
FROM MasterTable
ORDER BY ClassYear; --no table ref needed

Answer 2

It's property sorting those values as strings. If you want them in numerical order, try something like Cast(MasterTable.ClassYear AS int) , either in the select or in the order by, or both, depending on how you end up structuring your query.

And instead of SELECT ..., "1" As [ClassYear] , write SELECT ..., 1 As [ClassYear] .

Answer 3

You are returning the year as a string, not a number. That means that it's sorted as text, not numerically.

Either return the year as a number, or convert the value into a number when sorting it.