如何排序MySQL搜索结果的相关性？

Question

I'm using PDO to search a MySQL table for search results. My query looks like this

$sql = "SELECT * FROM users WHERE username LIKE :username OR name LIKE :name ORDER BY uniqueid DESC LIMIT 6";
$stmt = $conn->prepare($sql);
$stmt->bindValue(':username', '%'.$query.'%');
$stmt->bindValue(':name', $query.'%');

What I'm trying to accomplish is that in my results array, the results that match like this:

$query.'%'

Should appear before results that match like this:

'%'.$query.'%'

Is there a way to sort results by such relevance without two queries, preferably in pure SQL?

Answer 1

You could order the results by the index of $query in username and name :

SELECT * FROM users
    WHERE username LIKE :username OR name LIKE :name
ORDER BY uniqueid DESC, INSTR(:query, username), INSTR(:query, name) LIMIT 6

Note, however, that ordering by results of a function requires full table scan in MySQL.

Answer 2

您可以轻松使用以下查询：

$SQL = "SELECT * FROM users WHERE username LIKE :username OR name LIKE :name ORDER BY name LIKE :name DESC, uniqueid DESC LIMIT 6"; –

Answer 3

Well, Eugene's answer seems the most appropriate in this case. Provided below is an alternate solution to the problem in general which allows further customizations in terms of sorting the result :

If you have data like this :

Id  Name
1   Aabbee
2   Aabriella
3   Aada
4   bahlelah
5   cailelah
6   daielah
7   gaisha
8   Aisha
9   Aishath
10  dalelh
11  Eleasha

Then, you can use the following query:

select '1' as Relevance,ID, Name from MyTable where Name like 'el%' /*The results with the priority (or relevance) should be first */
union
select '2' as Relevance,ID, Name from MyTable where Name like '%el%' and Name not like 'el%' /* The lower priority results go here*/
order by Relevance

This will result in:

Relevance   ID    Name
    1       11    Eleasha
    2       2     Aabriella
    2       4     bahlelah
    2       5     cailelah
    2       6     daielah
    2       10    dalelh