How Can MySQL's GROUP BY Clause Concatenate Strings?

MySQL's GROUP BY Clause: Combining Strings

MySQL's powerful GROUP BY clause isn't limited to numerical aggregation. It can also efficiently concatenate strings associated with grouped data. This is especially helpful when dealing with tables containing multiple rows sharing a common identifier.

Consider this example table:

foo_id	foo_name
1	A
1	B
2	C

Our goal is to combine foo_name values for each unique foo_id, resulting in:

foo_id	foo_name
1	A, B
2	C

This transformation is achieved using the following SQL query:

<code class="language-sql">SELECT foo_id, GROUP_CONCAT(foo_name SEPARATOR ', ') FROM table GROUP BY foo_id;</code>

Query Explanation:

• GROUP BY foo_id: This groups rows based on the foo_id column, bringing together all foo_name values for each unique ID.
• GROUP_CONCAT(foo_name SEPARATOR ', '): This function concatenates the foo_name values within each group, using a comma and space as the separator.

The GROUP_CONCAT() function offers a SEPARATOR argument, allowing flexible customization of the delimiter between concatenated strings. For comprehensive details, refer to the official MySQL documentation: https://www.php.cn/link/18fc3b6cc1e55ccea877c161e2e9ba27

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