How to Integrate the Levenshtein Function into MySQL for PHP Search Applications?

Installing the Levenshtein Function in MySQL

Problem:

How can the Levenshtein distance function be incorporated into MySQL for use in PHP-based search applications?

Solution:

Adding the Levenshtein Function

To add the Levenshtein function to MySQL, follow these steps using MySQL Workbench:

1. Connect to your MySQL server.
2. Execute the following statement:

CREATE FUNCTION levenshtein(s1 VARCHAR(255), s2 VARCHAR(255)) RETURNS INT
BEGIN
  DECLARE len1 INT;
  DECLARE len2 INT;
  DECLARE i INT;
  DECLARE j INT;
  DECLARE c INT;
  DECLARE cost INT;
  DECLARE d INT;
  DECLARE tmp INT;

  SET len1 = LENGTH(s1);
  SET len2 = LENGTH(s2);
  DECLARE matrix[len1 + 1][len2 + 1] INT;

  FOR i = 0 TO len1 DO
    SET matrix[i][0] = i;
  END FOR;

  FOR j = 0 TO len2 DO
    SET matrix[0][j] = j;
  END FOR;

  FOR i = 1 TO len1 DO
    FOR j = 1 TO len2 DO
      IF s1[i] = s2[j] THEN
        SET cost = 0;
      ELSE
        SET cost = 1;
      END IF;
      SET d = matrix[i - 1][j] + 1;
      SET c = matrix[i][j - 1] + 1;
      SET tmp = matrix[i - 1][j - 1] + cost;
      IF d < c THEN
        IF d < tmp THEN
          SET matrix[i][j] = d;
        ELSE
          SET matrix[i][j] = tmp;
        END IF;
      ELSE
        IF c < tmp THEN
          SET matrix[i][j] = c;
        ELSE
          SET matrix[i][j] = tmp;
        END IF;
      END IF;
    END FOR;
  END FOR;

  RETURN matrix[len1][len2];
END

Example Usage

Once the Levenshtein function is added, you can use it in PHP as follows:

$query = "SELECT levenshtein('abcde', 'abced')";
$result = mysqli_query($link, $query);
$row = mysqli_fetch_array($result);
echo $row['levenshtein(abcde, abced)']; // Output: 2

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