MySQL UNION SELECT语句由两个不同的列顺序

Question

I have a table with a column called "myorder". I want to only order the first 5 elements in ascending order by using the column "myorder" and then the rest of the elements ordererd by id in descending order. I've tried but I don't seem to get this 100%. I have created a sqlfiddle with this simple example. Can anybody help me?

The order in the sqlfiddle should be: Blue, Brown, Yellow, Red, Green, Orange, Gray, Black, White.

Answer 1

Append this to the end of your sql statement:

ORDER BY FIELD(id, 3,4,5,1,2,9,8,7,6)

This will manually sort the results based on the id field in the specified order getting the colours in order.

Alternatively you could:

ORDER BY FIELD(NAME, BLUE,BROWN,YELLOW......)

Answer 2

Union does not preserves order, at least not in all databases. To get this done you need to select a fake column and use order on the results (total)

Here is a solution:

(

SELECT Id, myorder, myorder as fake, name from tbl WHERE myorder!=0) UNION 
(SELECT id, myorder, 2000 as fake,name  from tbl WHERE myorder=0) ORDER BY fake asc, id desc

This Will work in any case, as long as you keep the fake number high enough.

Answer 3

maybe try

SELECT * from tbl ORDER BY IF(myorder=0, 2147483647, myorder) ASC, id DESC

if by "first 5" you mean ones with nonzero myorder

Answer 4

Can we have NULL value instead of zero when myorder is not specified?

If so we can do this:

SELECT * from tbl ORDER BY -myorder DESC, id DESC

Fiddle:

http://sqlfiddle.com/#!2/ef9ee/4

Hint on forcing nulls to sort last: MySQL Orderby a number, Nulls last

Answer 5

Use a CASE statement and the following trick (for example):

SELECT *, 
CASE myorder
    WHEN 0 THEN id
    ELSE 99999999 - myorder
END AS ord
FROM tbl
ORDER BY ord DESC

SQL Fiddle