? CONCAT Function in SQL

The CONCAT() function is used to concatenate (join) two or more strings into one single string.

? Syntax

CONCAT(string1, string2, ..., stringN)

• Takes two or more string arguments.

• Returns a single string that is the combination of all input strings.

• If any argument is NULL, in most databases, it treats it as an empty string (behavior may vary).

? Examples

1. Concatenate two strings

SELECT CONCAT('Hello', ' ', 'World') AS greeting;-- Result: 'Hello World'

2. Concatenate columns

Suppose you have a table employees with columns first_name and last_name:

SELECT CONCAT(first_name, ' ', last_name) AS full_name FROM employees;

3. Handling NULL values (in MySQL)

SELECT CONCAT('Name: ', NULL, ' Smith') AS result;-- Result: 'Name:  Smith' (NULL treated as empty string)

? Notes

• In some databases (like SQL Server), use the + operator or CONCAT() (from SQL Server 2012+).

• For Oracle, use || operator for string concatenation:

SELECT first_name || ' ' || last_name AS full_name FROM employees;

If you want, I can provide examples for a specific database or show alternatives for concatenation!