MySQL ORDER BY取决于CASE顺序ASC或DESC

Question

I want based on a value queried from another table order ASC or DESC.

So something like this:

SELECT *
FROM table
ORDER BY 
    CASE (SELECT sorting from table2 WHERE table2.id = ?)
        WHEN 1 THEN table.date ASC END 
        WHEN 0 THEN table.date DESC END
    END

Is anything like that available in MySQL?

I've seen for MS-SQL Server some solution: how to order 2 SQL Fields in asc and desc dynamically

EDIT : I just saw I made a mistake in the description, fixed.

Answer 1

order by if((select sorting from table2 where table2.id = ?) = 1,
  unix_timestamp(table.date), -unix_timestamp(table.date))

negation works if your column is numeric. if it's a string, you might be able to find another function to map high values to low values...

Answer 2

T-SQL statements can't be constructed conditionally in the manner your suggesting.

You need to construct your query into a varchar, then perform an EXEC against the constructed string, along the lines of the following:

Declare @QueryString varchar(100)
Declare @Direction int

Select @direction = sorting
  from table2
 where table2.id=? //from your original, not clear how you are providing it

Set @QueryString = 'Select * from table order by yourField ' + case when @direction=1 then 'ASC' else 'DESC' end

Exec (@QueryString)

---

EDIT Presuming your order_by field is numeric, one trick you employ (although I'm not sure it would fall into the "best practices" camp) would be to multiply the value of the order by field by -1 to reverse the default order, eg

Select @Direction = sorting
  from table2
 where table2.id=? 

Select * 
  from table
  order by (case when @direction=1 then -1 else 1 end) *yourField