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PostgreSQL REVERSE() Function |
PostgreSQL REVERSE() Function |
In this tutorial, you will learn how to use the PostgreSQL REVERSE() function to reverse the characters within a string. |
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2024-01-28T10:36:42+00:00 |
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Summary: in this tutorial, you will learn how to use the PostgreSQL REVERSE()
function to reverse the characters within a string.
The REVERSE()
function accepts a string and returns a new string with the order of all characters reversed.
Here’s the syntax of the REVERSE()
function:
REVERSE(text)
In this syntax:
text
: The input string that you want to reverse.
The REVERSE()
function returns a string with the order of all the characters reversed.
The REVERSE()
function returns NULL
if the text
is NULL
.
Let’s explore some examples of using the REVERSE()
function.
The following example uses the REVERSE()
function to reverse the string "SQL"
:
SELECT REVERSE('SQL');
Output:
reverse
---------
LQS
(1 row)
We’ll use the customer
table from the sample database:
The following example uses the
REVERSE()
function to reverse the first names of customers:
SELECT
first_name,
REVERSE(first_name)
FROM
customer
ORDER BY
first_name;
Output:
first_name | reverse
-------------+-------------
Aaron | noraA
Adam | madA
Adrian | nairdA
Agnes | sengA
A palindrome is a string that reads the same forward and backward such as "radar"
.
You can use the REVERSE()
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 called words
to store the words:
CREATE TABLE words(
id SERIAL PRIMARY KEY,
word VARCHAR(255) NOT NULL
);
Second, insert some rows into the words
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 the word
column is a palindrome using the REVERSE()
function:
SELECT
word,
REVERSE(word),
(
word = REVERSE(word)
) palindrome
FROM
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)
- Use the PostgreSQL
REVERSE()
function to reverse the order of characters within a string.