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Home 2017 May PostgreSQL: Compare two String Similarity in percentage (pg_trgm module)

PostgreSQL: Compare two String Similarity in percentage (pg_trgm module)

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In this post, I am sharing small demonstration on, how to find similarity between Postgres strings in percentage?
PostgreSQL is a well known for a variety of string functions which are used for data analysis.

One of our developers is generating random token string manually for two columns, and now he is required to find similarity between this string.

In the PostgreSQL, you can use a pg_trgm module to find similarity based on trigram matching.

Below is a demonstration of this:

Create a table with sample data:

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CREATE TABLE tbl_SimilarString
(
Str1 TEXT
,Str2 TEXT
);
 
INSERT INTO tbl_SimilarString VALUES
('Anvesh Patel','Anvesh Pat')
,('dbrnd','dbrnd blog')
,('database dev','database developer')
,('postgres database','database postgres');

Install pg_trgm module:

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CREATE EXTENSION pg_trgm;

Use similarity():

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SELECT similarity(Str1,Str2) FROM tbl_SimilarString;

The result:

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similarity
------------
0.714286
0.545455
0.578947
1
(4 rows)

May 20, 2017Anvesh Patel
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Comments: 3
  1. Tony
    October 24, 2017 at 10:49 am

    There is an ability to use dbForge Data Compare for PostgreSQL https://www.devart.com/dbforge/postgresql/datacompare/ for data comparison and synchronization.

    ReplyCancel
  2. Akansha
    September 11, 2019 at 11:32 am

    Thanks for the solution.

    I have a similar problem with single column. there are millions of addresses in a single column and i want a match percentage of one value with others. How can i do that?

    ReplyCancel
  3. Akansha
    September 11, 2019 at 12:38 pm

    How to use similarity function on single column. I have a column with address values. I want to check similarity within column.

    ReplyCancel

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Anvesh Patel
Anvesh Patel

Database Engineer

May 20, 2017 3 Comments PostgreSQLAnvesh Patel, database, database research and development, dbrnd, pg_trgm, plpgsql, Postgres Query, postgresql, PostgreSQL Administrator, PostgreSQL Error, PostgreSQL Monitoring, PostgreSQL Performance Tuning, PostgreSQL Programming, PostgreSQL Tips and Tricks, similarity
About Me!

I'm Anvesh Patel, a Database Engineer certified by Oracle and IBM. I'm working as a Database Architect, Database Optimizer, Database Administrator, Database Developer. Providing the best articles and solutions for different problems in the best manner through my blogs is my passion. I have more than six years of experience with various RDBMS products like MSSQL Server, PostgreSQL, MySQL, Greenplum and currently learning and doing research on BIGData and NoSQL technology. -- Hyderabad, India.

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