Explicitly specify sort order for MySQL query (use an “IN” list)

Question

With a query like the following, the default will return in order of id of least to greatest even if the IN list is not in that order. In my situation the list will be supplied from some c# code.

How can I order the result set by the order of values in the IN list?

What I have:

SELECT * FROM example Where Id in (1,3,2);
returns: 
|---------------|---------------|
|       id      |    Value      |
|---------------|---------------|
|       1       |   example1    |
|---------------|---------------|
|       2       |   example2    |
|---------------|---------------|
|       3       |   example3    |
|---------------|---------------|

What I want is:

SELECT * FROM example Where Id in (1,3,2)
         Order By "Magic code here";
returns: 
|---------------|---------------|
|       id      |    Value      |
|---------------|---------------|
|       1       |   example1    |
|---------------|---------------|
|       3       |   example3    |
|---------------|---------------|
|       2       |   example2    |
|---------------|---------------|

Answer 1

You have two ways of doing this (see the fiddle here):

CREATE TABLE ex
(
  id INTEGER AUTO_INCREMENT PRIMARY KEY,
  value VARCHAR(10) NOT NULL
);

Populate the table:

INSERT INTO ex (value) VALUES
('example1'), ('example2'), ('example3');

And then the "magic sauce"...

SELECT * FROM ex ORDER BY field (id, 1, 3, 2); 

Result:

id  value
1   example1
3   example3
2   example2

This is a non-standard MySQL "trick".

A standards compliant way of doing this would be:

SELECT * FROM ex
ORDER BY 
  CASE id
    WHEN 1 THEN 1
    WHEN 2 THEN 3
    WHEN 3 THEN 2
  END;

Result:

id  value
1   example1
3   example3
2   example2

See the PostgreSQL fiddle here. PostgreSQL is one of the (possibly the) most standards compliant RDBMS systems out there, so that's why I used it for comparison purposesl

p.s. welcome to the forum!