MySQL sort by number of occurrences

Question

I am doing a search in two text fields called Subject and Text for a specific keyword. To do this I use the LIKE statement. I have encount

Answer 1

// escape $keyword for mysql
$keyword = strtolower('Keyword');
// now build the query
$query = <<<SQL
    SELECT *,
    ((LENGTH(`Subject`) - LENGTH(REPLACE(LOWER(`Subject`), '{$keyword}', ''))) / LENGTH('{$keyword}')) AS `CountInSubject`,
    ((LENGTH(`Text`) - LENGTH(REPLACE(LOWER(`Text`), '{$keyword}', ''))) / LENGTH('{$keyword}')) AS `CountInText`
    FROM `News`
    WHERE (`Text` LIKE '%{$keyword}%' OR `Subject` LIKE '%{$keyword}%')
    ORDER BY (`CountInSubject` + `CountInText`) DESC;
SQL;

Returns number of occurrences in each field and sorts by that.

The 'keyword' needs to be lower cased for this to work. I don't think it's really fast, performance wise as it needs to lower-case fields and there's no case-insensitive search in MySQL afaik.

You could index each news item (subject and text) by words and store in another table with news_id and occurrence count and then match against that.

Answer 2

Below query can give you the no.of occurrences of string appears in both columns i.e text and subject and will sort results by the criteria but this will not be a good solution performance wise its better to sort the results in your application code level

SELECT *,
(LENGTH(`Text`) - LENGTH(REPLACE(`Text`, 'Keyword', ''))) / LENGTH('Keyword')
+
(LENGTH(`Subject`) - LENGTH(REPLACE(`Subject`, 'Keyword', ''))) / LENGTH('Keyword') `occurences`
 FROM 
`Table`
 WHERE (Text LIKE '%Keyword%' OR Subject LIKE '%Keyword%')
ORDER BY `occurences`  DESC

Fiddle Demo

Suggested by @lserni a more cleaner way of calculation of occurrences

SELECT *,
(LENGTH(`Text`) - LENGTH(REPLACE(`Text`, 'test', ''))) / LENGTH('test') `appears_in_text`,

(LENGTH(`Subject`) - LENGTH(REPLACE(`Subject`, 'test', ''))) / LENGTH('test') `appears_in_subject`,

(LENGTH(CONCAT(`Text`,' ',`Subject`)) - LENGTH(REPLACE(CONCAT(`Text`,' ',`Subject`), 'test', ''))) / LENGTH('test') `occurences`
 FROM 
`Table1`
 WHERE (TEXT LIKE '%test%' OR SUBJECT LIKE '%test%')
ORDER BY `occurences`  DESC

Fiddle Demo 2

Answer 3

You want SUM instead. Count will count how many records have non-null values, which means ALL matches and NON-matches will be counted.

SELECT *, SUM(Text LIKE '%Keyword') AS total_matches
...
ORDER BY total_matches

SUM() will count up how many boolean true results the LIKE produces, which will be typecast to integers, so you get a result like 1+1+1+0+1 = 4, instead of the 5 non-nulls count.