227 UTL_MATCH

The UTL_MATCH package facilitates matching two records. This is typically used to match names, such as two First Names or two Last Names.

This chapter contains the following topics:

Using UTL_MATCH
- Overview
- Security Model
Summary of UTL_MATCH Subprograms

Using UTL_MATCH

Overview
Security Model

Overview

"Edit Distance" also known as "Levenshtein Distance "(named after the Russian scientist Vladimir Levenshtein, who devised the algorithm in 1965), is a measure of Similarity between two strings, s1 and s2. The distance is the number of insertions, deletions or substitutions required to transform s1 to s2.�

The Edit Distance between strings "shackleford" and "shackelford" = 2

The "Jaro-Winkler algorithm" is another way of calculating Edit distance between two strings. This method, developed at the U.S. Census, is a String Comparator measure that gives values of partial agreement between two strings. The string comparator accounts for length of strings and partially accounts for typical human errors made in alphanumeric strings.

Table 227-1 shows similarity values returned by Jaro-Winkler and Edit Distance

Table 227-1 Comparison between normalized values returned by Jaro-Winkler and Edit Distance algorithms

String 1	String 2	Jaro Winkler	Edit Distance
Dunningham	Cunnigham	89	80
Abroms	Abrams	92	83
Lampley	Campley	90	86
Marhta	Martha	96	67
Jonathon	Jonathan	95	88
Jeraldine	Geraldine	92	89

Security Model

The UTL_MATCH package runs with definer's rights. UTL_MATCH must be created under SYS. Operations provided by this package are performed with SYS privileges.

Summary of UTL_MATCH Subprograms

Table 227-2 DBMS_ALERT Package Subprograms

Subprogram	Description
EDIT_DISTANCE Function	Calculates the number of changes required to transform string-1 into string-2
EDIT_DISTANCE_SIMILARITY Function	Calculates the number of changes required to transform string-1 into string-2, returning a value between 0 (no match) and 100 (perfect match)
JARO_WINKLER Function	Calculates the measure of agreement between string-1 and string-2
JARO_WINKLER_SIMILARITY Function	Calculates the measure of agreement between string-1 and string-2, returning a value between 0 (no match) and 100 (perfect match)

EDIT_DISTANCE Function

This function calculates the number of insertions, deletions or substitutions required to transform string-1 into string-2.

Syntax

UTL_MATCH.EDIT_DISTANCE (
   s1  IN  VARCHAR2, 
   s2  IN  VARCHAR2) 
 RETURN PLS_INTEGER;�

Parameters

Table 227-3 EDIT_DISTANCE Function Parameters

Parameter	Description
`s1`	The string to be transformed
`s2`	The string into which `s1` is to be transformed

Examples

SELECT UTL_MATCH.EDIT_DISTANCE('shackleford', 'shackelford') FROM DUAL;  
-------------
returns 2

EDIT_DISTANCE_SIMILARITY Function

This function calculates the number of insertions, deletions or substations required to transform string-1 into string-2, and returns the Normalized value of the Edit Distance between two Strings. The value is typically between 0 (no match) and 100 (perfect match).�

Syntax

UTL_MATCH.EDIT_DISTANCE_SIMILARITY (
   s1  IN  VARCHAR2, 
   s2  IN  VARCHAR2) 
 RETURN PLS_INTEGER;�

Parameters

Table 227-4 EDIT_DISTANCE_SIMILARITY Function Parameters

Parameter	Description
`s1`	The string to be transformed
`s2`	The string into which `s1` is to be transformed

Examples

SELECT UTL_MATCH.EDIT_DISTANCE_SIMILARITY('shackleford', 'shackelford') FROM DUAL;
--------------
returns 82

JARO_WINKLER Function

This function calculates the measure of agreement between two strings.�

Syntax

UTL_MATCH.JARO_WINKLER (
   s1  IN  VARCHAR2, 
   s2  IN  VARCHAR2) 
 RETURN BINARY_DOUBLE;�

Parameters

Table 227-5 JARO_WINKLER Function Parameters

Parameter	Description
`s1`	Input
`s2`	input

Examples

SELECT UTL_MATCH.JARO_WINKLER('shackleford', 'shackelford') FROM DUAL;
--------------
returns 9.818E-001

JARO_WINKLER_SIMILARITY Function

This function calculates the measure of agreement between two strings, and returns a score between 0 (no match) and 100 (perfect match).�

Syntax

UTL_MATCH.JARO_WINKLER (
   s1  IN  VARCHAR2, 
   s2  IN  VARCHAR2) 
 RETURN PLS_INTEGER;�

Parameters

Table 227-6 JARO_WINKLER Function Parameters

Parameter	Description
`s1`	Input
`s2`	input

Examples

SELECT UTL_MATCH.JARO_WINKLER_SIMILARITY('shackleford', 'shackelford') FROM DUAL;
--------------
returns 98