Unveiling String Distances: A Dive into Levenshtein and Jaro Distances in Databases
Tags: database, distance, oracle, stringdistance
Published: 2023-07-14 20:06:41


Measuring the similarity or dissimilarity between strings is a fundamental task in various domains, including natural language processing, data mining, and database management systems. Particularly in the realm of databases, where dealing with extensive textual data is common, accurately assessing the similarity or dissimilarity between strings becomes crucial for essential operations like data matching, record linkage, and fuzzy searching. In this blog post, we will explore two widely used string distance metrics: the Levenshtein distance and the Jaro distance. Additionally, we will delve into the practical applications of these distances within databases, using Oracle Database as a prime example. Join us as we dive into the intricacies of string distances and uncover their invaluable role in the database landscape!

### **Levenshtein Distance:**
The Levenshtein distance, also known as the edit distance, quantifies the minimum number of operations required to transform one string into another. The allowed operations are typically insertion, deletion, and substitution of a single character. Named after the Soviet mathematician Vladimir Levenshtein, this distance metric has found extensive applications in areas such as spell checking and DNA sequence alignment.

**Calculation of Levenshtein Distance:**
To calculate the Levenshtein distance between two strings, we employ a dynamic programming algorithm. The algorithm constructs a matrix where each cell represents the distance between substrings of the input strings. By populating this matrix iteratively, we can find the Levenshtein distance.

Let's consider an example:
String 1: "kitten"
String 2: "sitting"

Using the Levenshtein algorithm, we construct the following matrix:

  	   	 	   	0	1	2	3	4	5
  	   	 	   	|	s	i	t	t	i	n	g
  	   	 	-------------------------
  	0	|	0	1	2	3	4	5	6	7
  	k	|	1	1	2	3	4	5	6	7
  	i	|	2	2	1	2	3	4	5	6
  	t	|	3	3	2	1	2	3	4	5
  	t	|	4	4	3	2	1	2	3	4
  	e	|	5	5	4	3	2	2	3	4
  	n	|	6	6	5	4	3	3	2	3

The value at the bottom-right corner of the matrix, in this case, 3, represents the Levenshtein distance between "kitten" and "sitting." Thus, a minimum of three operations is required to transform "kitten" into "sitting" (substitute 'k' with 's', substitute 'e' with 'i', and insert 'g' at the end).

### **Jaro Distance:**
The Jaro distance is a measure of similarity between two strings. It considers the number of matching characters and the transpositions of those characters within a certain window. Unlike the Levenshtein distance, the Jaro distance does not involve insertions or deletions. The Jaro distance is commonly used in record linkage and fuzzy searching applications.

**Calculation of Jaro Distance:**
The Jaro distance calculation involves several steps. Firstly, we count the number of matching characters (characters in string 1 that appear in string 2) and the number of transpositions (characters in string 1 that appear in string 2 but are not in the same position). Using these values, we calculate the Jaro similarity coefficient. Finally, the Jaro distance is obtained by subtracting the Jaro similarity coefficient from 1.

### Using String Distances in Databases:
Oracle Database, a widely used relational database management system, provides built-in functionality to leverage string distances for various tasks. The UTL_MATCH package in Oracle Database offers functions such as UTL_MATCH.EDIT_DISTANCE and UTL_MATCH.JARO_WINKLER_DISTANCE, which enable developers to calculate the Levenshtein and Jaro distances respectively.

For instance, UTL_MATCH.EDIT_DISTANCE, which allows for efficient comparison of two strings and computation of their Levenshtein distance. This functionality proves immensely valuable in data matching and record linkage tasks within large datasets, as it aids in the identification of potential duplicates or matches. By defining a threshold for the Levenshtein distance, database professionals can tailor the sensitivity of the matching process to their specific needs. Integrating this function into SQL queries or PL/SQL procedures streamlines the identification and resolution of duplicates, thereby ensuring data accuracy and maintaining data integrity. With the ability to customize and automate the matching process, organizations can effectively manage their data and make informed decisions based on accurate and consolidated information.


Similarly, UTL_MATCH.JARO_WINKLER_DISTANCE can be utilized to measure the similarity between strings using the Jaro distance. This is valuable in fuzzy searching scenarios, where approximate matching is required to handle typos, abbreviations, or variations in data entry.

By utilizing these string distance functions within the context of Oracle Database, developers and database administrators can optimize data matching, record linkage, and fuzzy searching operations. These distances play a pivotal role in the database landscape by improving data quality, enhancing search capabilities, and streamlining data integration processes.



To explore more about string distances, check out [this](https://en.wikipedia.org/wiki/String_metric) comprehensive guide on various distance metrics and distance in [oracle](https://docs.oracle.com/database/121/ARPLS/u_match.htm#ARPLS352)

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