SQL CONCAT Function
Quick summary: The SQL CONCAT() function joins multiple strings into one.
SQL CONCAT Syntax
CONCAT(string1, string2, ...)SQL
SQL CONCAT Basic examples
SELECT CONCAT(first_name, ' ', last_name) FROM users;SQL
Output:
Full namesConcatenates string values.
SQL CONCAT Real-world usage
SELECT CONCAT('Order #', id) FROM orders;SQL
Output:
Order labelsBuilds human-readable strings.
SQL CONCAT Edge cases
SELECT CONCAT(NULL, 'abc');SQL
Output:
NULLIf any argument is NULL, result is NULL (MySQL behavior).
SQL CONCAT Common mistakes
Concatenating NULL values
NULL propagates through CONCAT.
Incorrect
CONCAT(first_name, last_name)Correct
CONCAT(COALESCE(first_name,''), COALESCE(last_name,''))Use COALESCE to avoid NULL results.
SQL CONCAT Frequently Asked Questions
What does CONCAT() do in SQL?
Combines multiple strings into one.
Use case of CONCAT()?
Building full names or messages.
Syntax?
CONCAT(str1, str2, ...).
Handles NULL?
Returns NULL if any argument is NULL (depends on DB).
Common mistake?
Not handling NULL values.
Alternative?
|| operator (DB-specific).
Return type?
String.
Performance?
Fast.
Supports numbers?
Yes, auto-cast.
Used in SELECT?
Yes.
Used in formatting?
Yes.
Best practice?
Handle NULL with COALESCE.