As with any other data type in SQL, strings can be worked on and joined through a process called concatenation, which combines strings. Although some SQL dialects support the use of the + operator for this purpose, it is best to use the CONCAT() function, which is more universally accepted.
In this blog, we’ll explain which SQL versions and platforms support the CONCAT() function and why it is considered the best approach.
What is CONCAT() in SQL?
The CONCAT() function joins two or more strings into one. It is an ANSI SQL standard and supported by most modern relational database systems.
Syntax:
Example:
Why Use CONCAT() Instead of +?
1. Cross-Database Compatibility
Not all SQL databases use + for string concatenation:
| Database | Supports + for strings? | Supports CONCAT()? |
|---|---|---|
| SQL Server | ✅ Yes | ✅ Yes (2012+) |
| MySQL | ❌ No (+ is numeric) | ✅ Yes |
| PostgreSQL | ❌ No (+ is numeric) | ✅ Yes (since 9.1) |
| Oracle | ❌ No (+ is numeric) | ✅ Yes (from 10g) |
| SQLite | ❌ No (+ is numeric) | ✅ Yes (from 3.8.3) |
+ might work in SQL Server, but it will fail in MySQL or PostgreSQL. So for portable SQL queries, CONCAT() is the safer choice.Automatic NULL Handling:
With +, if any value is NULL, the result becomes NULL in some databases:
This makes CONCAT() more robust when working with nullable columns.
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