avoid Sorting by the MYSQL IN Keyword

Question

When querying the db for a set of ids, mysql doesnot provide the results in the order by which the ids were specified. The query i am using is the following:

Answer 1

If you want to order your result by id in the order specified in the in clause you can make use of FIND_IN_SET as:

SELECT id ,title, date 
FROM Table 
WHERE id in (7,1,5,9,3)
ORDER BY FIND_IN_SET(id,'7,1,5,9,3')

Answer 2

The WHERE clause in SQL does not affect the sort order; the ORDER BY clause does that.

If you don't specify a sort order using ORDER BY, SQL will pick its own order, which will typically be the order of the primary key, but could be anything.

If you want the records in a particular order, you need to specify an ORDER BY clause that tells SQL the order you want.

If the order you want is based solely on that odd sequence of IDs, then you'd need to specify that in the ORDER BY clause. It will be tricky to specify exactly that. It is possible, but will need some awkward SQL code, and will slow down the query significantly (due to it no longer using a key to find the records).

If your desired ID sequence is because of some other factor that is more predictable (say for example, you actually want the records in alphabetical name order), you can just do ORDER BY name (or whatever the field is).

If you really want to sort by the ID in an arbitrary sequence, you may need to generate a temporary field which you can use to sort by:

SELECT *,
CASE id
  WHEN 7 THEN 1
  WHEN 1 THEN 2
  WHEN 5 THEN 3
  WHEN 3 THEN 4
  WHEN 9 THEN 5
END AS mysortorder
FROM mytable
WHERE id in (7,1,5,9,3)
ORDER BY mysortorder;

Answer 3

The behaviour you are seeing is a result of query optimisation, I expect that you have an index on id so that the IN statement will use the index to return records in the most efficient way. As an ORDER BY statement has not been specified the database will assume that the order of the return records is not important and will optimise for speed. (Checkout "EXPLAIN SELECT")

CodeAddicts or Spudley's answer will give the result you want. An alternative is assigning a priority to the id's in "mytable" (or another table) and using this to order the records as desired.

Answer 4

There is no auto-sorting or default sorting going on. The sorting you're seeing is most likely the natural sorting of rows within the table, ie. the order they were inserted. If you want the results sorted in some other way, specify it using an ORDER BY clause. There is no way in SQL to specify that a sort order should follow the ordering of items in an IN clause.