REPLACE()

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Overview

The REPLACE() function looks for and replaces a substring with a new one in a string. This function is often used to update the outdated or spelling mistakes in data that require an amendment.

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Syntax

The syntax for REPLACE() function is as follows:

REPLACE(string, old_substring, new_substring)

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Parameters

The syntax requires three parameters, explained below:

• string: string that you want to replace
• old_substring: substring that you want to replace (all parts will be replaced if it appears multiple times in the string)
• new_substring: new substring that will replace the old one

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Examples

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Basic usage

In this example we will focus on a basic usage of the REPLACE() function, so we can understand on real example how it works.

SELECT REPLACE ('NewDatabase', 'New', 'Oxla');

The REPLACE() function will find all occurrences of the ‘New’ substring in the ‘NewDatabase’ string and replace it with the ‘Oxla’ substring, producing the following output:

+---------------------+
| f                   |
+---------------------+
| OxlaDatabase        |
+---------------------+

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Replacing specified values in a table

This example shows how to replace the values of a specific column in a table. For the needs of this example, we will create a new table named extracurriculars with club and category columns and insert the values into the respective columns.

CREATE TABLE hobby (
  club text,
  category text
);
INSERT INTO hobby 
    (club, category) 
VALUES 
    ('Bridge','group'),
    ('Painting','individual'),
    ('Basketball','group'),
    ('Volleyball','group');

Once that is done, we can retrieve all values from the table using the following query:

SELECT * FROM hobby;

+------------+---------------+
| club       | category      |
+------------+---------------+
| Bridge     | group         |
| Painting   | individual    |
| Basketball | group         |
| Volleyball | group         |
+--------------+-------------+

What we would do here is to replace the ‘group’ values in the category column with ‘sports’:

SELECT REPLACE(category, 'group', 'sports') from hobby;
``` 

```sql
+--------------+
| f            |
+--------------+
| sports       |
| individual   |
| sports       |
| sports       |
+--------------+

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Removing a substring from a stirng

In the following example, we will show how to remove a substring from a string using the REPLACE() function. In this case we want to find all occurences of ‘Friends’ substring in ‘Hello Friends’ string and get rid of it:

SELECT REPLACE('Hello Friends', 'Friends', '');

+-----------+
| f         |
+-----------+
| Hello     |
+-----------+

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Replacing multiple patterns

The following example uses the REPLACE() function to replace multiple patterns of the given string:

SELECT REPLACE(REPLACE(REPLACE(REPLACE('2*[9-5]/{4+8}', '[', '('), ']', ')'), '{', '('), '}', ')');

We can see that the REPLACE() function is called multiple times to replace the corresponding string as specified:

• [] into ()
• {} into ()

+------------------+
| f                |
+------------------+
| 2*(9-5)/(4-8)    |
+------------------+