sql >> データベース >  >> RDS >> Mysql

MySQL-これにはどのハッシュアルゴを使用する必要がありますか?

    おそらく、levenshteinアルゴリズム を実装できます。 ストアド関数としてmysqlに追加します。以下に例を示します。これがお役に立てば幸いです:

    DELIMITER //
    CREATE FUNCTION levenshtein( s1 VARCHAR(255), s2 VARCHAR(255) )
      RETURNS INT
      DETERMINISTIC
      BEGIN
        DECLARE s1_len, s2_len, i, j, c, c_temp, cost INT;
        DECLARE s1_char CHAR;
        -- max strlen=255
        DECLARE cv0, cv1 VARBINARY(256);
        SET s1_len = CHAR_LENGTH(s1), s2_len = CHAR_LENGTH(s2), cv1 = 0x00, j = 1, i = 1, c = 0;
        IF s1 = s2 THEN
          RETURN 0;
        ELSEIF s1_len = 0 THEN
          RETURN s2_len;
        ELSEIF s2_len = 0 THEN
          RETURN s1_len;
        ELSE
          WHILE j <= s2_len DO
            SET cv1 = CONCAT(cv1, UNHEX(HEX(j))), j = j + 1;
          END WHILE;
          WHILE i <= s1_len DO
            SET s1_char = SUBSTRING(s1, i, 1), c = i, cv0 = UNHEX(HEX(i)), j = 1;
            WHILE j <= s2_len DO
              SET c = c + 1;
              IF s1_char = SUBSTRING(s2, j, 1) THEN 
                SET cost = 0; ELSE SET cost = 1;
              END IF;
              SET c_temp = CONV(HEX(SUBSTRING(cv1, j, 1)), 16, 10) + cost;
              IF c > c_temp THEN SET c = c_temp; END IF;
                SET c_temp = CONV(HEX(SUBSTRING(cv1, j+1, 1)), 16, 10) + 1;
                IF c > c_temp THEN 
                  SET c = c_temp; 
                END IF;
                SET cv0 = CONCAT(cv0, UNHEX(HEX(c))), j = j + 1;
            END WHILE;
            SET cv1 = cv0, i = i + 1;
          END WHILE;
        END IF;
        RETURN c;
      END; 
    

    ソース http://www.artfulsoftware.com/infotree/queries.php#552 (DELIMITER //を追加することで修正されました )

    テストサンプルスクリプト

    <?php
    //I inserted these test words into a test database
    $words = 'back, lack, pack, rack, sack, tack, yak, black, knack, quack, slack, smack, snack, stack, track, whack, attack,bale, fail, hail, mail, male, nail, pail, tale, rail, sail, stale, scale, snail, whale, detail, email,air, bare, care, chair, dare, fair, hair, pair, rare, wear, chair, flare, stare, scare, share, spare, square, there, where, aware, beware, compare, declare, despair, prepare, repair, unfair,ache, bake, fake, lake, make, rake, take, brake, break, flake, quake, snake, steak, awake, mistake,all, ball, call, doll, hall, fall, tall, crawl, small, baseball, football,an, can, fan, man, pan, ran, tan, van, plan, scan, span, began,and, band, hand, land, sand, bland, command, demand, expand, stand, understand,cap, gap, map, nap, tap, zap, chap, clap, flap, slap, snap, strap, trap, wrap,are, bar, car, far, jar, tar, star, scar, afar, guitar,at, bat, fat, mat, pat, rat, sat, flat, that, splat, combat,ate, date, fate, mate, late, gate, rate, wait, crate, great, plate, skate, slate, state, straight, trait, weight, create,bed, dead, fed, head, led, read, red, said, bread, fled, spread, thread, tread, instead,bell, fell, sell, well, yell, shell, smell, spell, farewell, hotel, motel,den, hen, men, pen, ten, glen, then, when, wren, again,bet, get, jet, let, met, pet, set, vet, wet, yet, threat, barrette, reset, upset,bin, chin, in, pin, tin, grin, thin, twin, skin, begin, within,king, ring, sing, wing, zing, bring, cling, fling, sling, spring, sting, string, swing, thing,bit, fit, hit, it, kit, lit, pit, sit, flit, knit, quit, skit, slit, spit, split, admit, commit, permit,bite, kite, bright, fight, fright, knight, night, might, right, tight, white, write, delight, tonight,go, hoe, low, mow, row, sew, toe, blow, crow, dough, flow, know, glow, grow, know, show, slow, snow, stow, though, throw, ago, although, below,cot, dot, got, hot, lot, not, pot, rot, tot, bought, fought, knot, taught, shot, spot, squat, forgot,crowned, found, ground, hound, mound, pound, round, sound, wound, around, surround,bows, hose, nose, rose, toes, blows, flows, froze, grows, those,cub, rub, sub, tub, club, stub, scrub, shrub ,bun, fun, gun, one, run, son, sun, ton, won, done, none, begun, outdone, undone';
    
    //A Class for db connection
    Class DB{
        private $db;
    
        function __construct($host,$dbname,$user,$pass){
            $this->dbhost = $host;
            $this->dbname = $dbname;
            $this->dbuser = $user;
            $this->dbpass = $pass;
        }
    
        private function connect(){
            if (!$this->db instanceof PDO){
                $this->db = new PDO('mysql:dbname='.$this->dbname.';host='.$this->dbhost, $this->dbuser, $this->dbpass);
                $this->db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
            }
        }
    
        //A Model method for the levenshtein_query.
        public function levenshtein_query($word,$dist){
            $this->connect();
            $sql = "SELECT `word` FROM `words` WHERE levenshtein( :word ,`word` ) BETWEEN 0 AND $dist";
            $statement = $this->db->prepare($sql);
            $statement->bindParam(':word', $word, PDO::PARAM_STR);
            $statement->execute();
            return $statement->fetchAll(PDO::FETCH_ASSOC);
        }
    }
    
    //ini the model class
    $model = new DB('localhost','test_db','root','');
    
    //The Word posted
    $word = 'eet';
    $result = $model->levenshtein_query($word,1);
    
    print_r($result);
    /*
    //The Result
    Array
    (
        [0] => Array
            (
                [word] => bet
            )
    
        [1] => Array
            (
                [word] => get
            )
    
        [2] => Array
            (
                [word] => jet
            )
    
        [3] => Array
            (
                [word] => let
            )
    
        [4] => Array
            (
                [word] => met
            )
    
        [5] => Array
            (
                [word] => pet
            )
    
        [6] => Array
            (
                [word] => set
            )
    
        [7] => Array
            (
                [word] => vet
            )
    
        [8] => Array
            (
                [word] => wet
            )
    
        [9] => Array
            (
                [word] => yet
            )
    
        [10] => Array
            (
                [word] => meet
            )
    
    )
    
    */
    

    おそらくそれは興味深いものです...




    1. Galera ClusterRecovery101-ネットワークパーティショニングの詳細

    2. SQLite Upper()のしくみ

    3. SQLiteで外部キー違反を見つける

    4. ユニオン対ユニオンオールのパフォーマンス