Introduction to PostgreSQL REVERSE() function

TheREVERSE() function accepts a string and returns a new string with the order of all characters reversed.

Here’s the syntax of theREVERSE() function:

REVERSE(text)

In this syntax:

• text: The input string that you want to reverse.

TheREVERSE() function returns a string with the order of all the characters reversed.

TheREVERSE() function returnsNULL if thetext isNULL.

MySQL REVERSE() function examples

Let’s explore some examples of using theREVERSE() function.

1) Basic PostgreSQL REVERSE() function example

The following example uses theREVERSE() function to reverse the string"SQL":

SELECT REVERSE('SQL');

Output:

reverse--------- LQS(1 row)

2) Using the PostgreSQL REVERSE() function with table data

We’ll use thecustomer table from thesample database:

The following example uses theREVERSE() function to reverse the first names of customers:

SELECT  first_name,  REVERSE(first_name)FROM  customerORDER BY  first_name;

Output:

first_name  |   reverse-------------+------------- Aaron       | noraA Adam        | madA Adrian      | nairdA Agnes       | sengA

3) Using REVERSE() function to detect palindromes

A palindrome is a string that reads the same forward and backward such as"radar".

You can use theREVERSE() function to reverse a string and then compare the reversed string with the original string to determine if it is a palindrome. For example:

First,create a new table calledwords to store the words:

CREATE TABLE words(  idSERIAL PRIMARY KEY,  wordVARCHAR(255)NOT NULL);

Second,insert some rows into thewords table:

INSERT INTO words(word)VALUES('radar'), ('level'),('civic'),('man'),('12321'),('madam')RETURNING*;

Output:

id | word----+-------  1 | radar  2 | level  3 | civic  4 | man  5 | 12321  6 | madam(6 rows)

Third, determine if a value in theword column is a palindrome using theREVERSE() function:

SELECT  word,  REVERSE(word),  (    word = REVERSE(word)  )palindromeFROM  words;

Output:

word  | reverse | palindrome-------+---------+------------ radar | radar   | t level | level   | t civic | civic   | t man   | nam     | f 12321 | 12321   | t madam | madam   | t(6 rows)

Summary

• Use the PostgreSQLREVERSE() function to reverse the order of characters within a string.

Last updated onJanuary 28, 2024

On this page

• Introduction to PostgreSQL REVERSE() function
• MySQL REVERSE() function examples
• Summary