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mysqlsql-like

mysql like to match complete word or beginning of word on string


Given a search string I need to select every record where (in the field the search is performed on) there is at least one word that begins with the given text.

For example:

'John Doe'

Have to be be selected with search strings like:

'joh'
'do'
'JOHN doe'

Have not to be selected with

'ohn'
'oe'

I need (possibly) to avoid full text search.

What I've found to work is

$query = 'SELECT * FROM MYTABLE WHERE SEARCHFIELD LIKE "' . $searchText . '%"'
                                . 'OR SEARCHFIELD LIKE "% ' . $searchText . '%"'

I'm asking if there is a better way to do that.

(for "better way" I mean better performance or same performance but more elegant)

Also, as the query will be built up with a prepared statement, how should I unescape LIKE metacharacters in the search string?


Solution

  • As already stated in the question the query

    $query = 'SELECT * FROM MYTABLE WHERE SEARCHFIELD LIKE "' . $searchText . '%"'
                                    . 'OR SEARCHFIELD LIKE "% ' . $searchText . '%"'
    

    works for matching records where the SEARCHFIELD contains a word that begins with (or is equal to) $searchText


    Regarding performance I've made a test on my development machine MBP 2,2 GHz i7 quad core:

    Searching for a word on 4.000 records takes around 40 milliseconds.

    Records are normally indexed (no fulltext).

    I have few thousands records and the query doesn't run very often so for me is good.
    The solution may not be suitable for other contexts.


    To build a prepared statement with the above query I used the technique described here:

    Escaping MySQL wild cards

    The resulting code is as follows:

    function like($s, $e)
    {
        return str_replace(array($e, '_', '%'), array($e . $e, $e . '_', $e . '%'), $s);
    }
    
    /* ... */
    
    /* create a prepared statement */
    $stmt = $mysqli->prepare(
        'SELECT * FROM MYTABLE WHERE SEARCHFIELD LIKE ? ESCAPE "=" OR SEARCHFIELD LIKE ? ESCAPE "="'
    ); 
    
    if( $stmt )
    {
        /* escape the text */
        $escSearchText = like( $searchText, "=" );
    
        /* 'like' parameters */
        $like1 = $escSearchText . "%";
        $like2 = "%" . $escSearchText . "%";
    
        /* bind parameters for markers */
        $stmt->bind_param( "ss", $like1, $like2 );
    
    /* ... */