In databases, manipulating, querying, and transforming data is fundamental. SQL Server provides us with many functions to help in these tasks.
Among them is the REVERSE function – a simple yet valuable function that allows us to reverse the characters of a string.
SQL Server Reverse Function
As the name suggests, the REVERSE function returns the reverse of a string value. For instance, if your input is DATABASE, the function will return ESABATAD.
Function Syntax
The following shows the syntax of the reverse() function in SQL Server
REVERSE(input_string)
- input_string - The string value we want to reverse.
Examples
Example 1 - Basic Usage
Let us start with a basic example
SELECT REVERSE('DATABASE') AS Result;
Output:
Result
--------------
ESABATAD
Example 2 - Reversing Data from a Table
Suppose we have a table named Users with a column FirstName:
| UserID | FirstName |
|---|---|
| 1 | Alice |
| 2 | Bob |
| 3 | Charlie |
To reverse the FirstName of each user, we can run a query as:
SELECT UserID, FirstName, REVERSE(FirstName) AS Results
FROM Users;
The resulting table is as shown:
| UserID | FirstName | Results |
|---|---|---|
| 1 | Alice | ecilA |
| 2 | Bob | boB |
| 3 | Charlie | eilrahC |
Example 3 - Detecting Palindromes
A palindrome is a word, phrase, number, or other sequence of characters that reads the same forward and backward (ignoring spaces, punctuation, and capitalization). Using the REVERSE function, we can easily identify palindromic words:
SELECT Word
FROM table
WHERE Word = REVERSE(Word);
Example 4 - Reversing Numbers
While the REVERSE function is primarily used with strings, it can also reverse numbers, but remember, numbers are implicitly converted to strings before reversing.
SELECT REVERSE(12345) AS Result;
Output:
Result
--------------
54321
Creative Uses
Password Strength
You can introduce an additional layer of complexity in passwords by storing a combination of the original password and its reversed version.
Data Obfuscation:
While it's not a secure encryption method, reversing strings can be one of the multiple steps in obfuscating data.
NOTE: Be cautious when reversing Unicode strings, especially those combining characters, as reversing might lead to unexpected results.
Conclusion
The SQL Server REVERSE function offers a handy way to manipulate string data. While it may seem like a simple tool, it can become an influential asset in your SQL toolkit when combined with other SQL functions and constructs.
