String concatenation with MySQL - Part 1String concatenation with MySQL - Part 1

Posted March 4th, 2009 in MySql (Updated December 16th, 2009)

MySQL has a number of string handling functions including functions to concatenate text or database columns into a single column in the resultset. I'm always forgetting that the function is CONCAT and not CONCATENATE so maybe by writing about it I will actually remember...

Example data

The example table used in this post is called "products" and contains the following data:

+------------+------+--------------------+--------+
| product_id | name | description        | price  |
+------------+------+--------------------+--------+
|          1 | Foo  | Blah blah foo blah |  55.00 |
|          2 | Bar  | Blah blah bar blah | 102.00 |
|          3 | Baz  | Blah blah baz blah |  87.50 |
|          4 | Bat  | Blah blah bat blah |  42.00 |
+------------+------+--------------------+--------+

Using concat to concatenate fields and strings

To return a resultset which contains the name and description columns as a single string column where the name and description values are separated by a dash, you could do this:

SELECT CONCAT(name, ' - ', description) FROM products;

which would give us a resultset like this:

+----------------------------------+
| CONCAT(name, ' - ', description) |
+----------------------------------+
| Foo - Blah blah foo blah         |
| Bar - Blah blah bar blah         |
| Baz - Blah blah baz blah         |
| Bat - Blah blah bat blah         |
+----------------------------------+

Note that the column name is "CONCAT(name, ' - ', description)" so you'd either want to access the column using a numeric index or use "AS" syntax to give it a more user friendly name:

 SELECT CONCAT(name, ' - ', description) AS name_description FROM products;
+--------------------------+
| name_description         |
+--------------------------+
| Foo - Blah blah foo blah |
| Bar - Blah blah bar blah |
| Baz - Blah blah baz blah |
| Bat - Blah blah bat blah |
+--------------------------+

And finally, don't make my mistake and think the function is called CONCATENATE otherwise you'll get this error:

ERROR 1305 (42000): FUNCTION test.CONCATENATE does not exist

So that's how to use the CONCAT function in MySQL to concatenate strings. While this probably isn't a very realistic example to have used it does illustrate how to use the function and I've had to use it a number of times in my own projects.

CONCAT_WS

Be sure to read the follow up post to this one which looks at the CONCAT_WS function which uses a glue string to join the fields together.

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