Abstract: This article introduces the concept and usage of the GROUP_CONCAT() function in MySQL database in detail. Through examples and output results, it shows how to use the GROUP_CONCAT() function to splice the grouped data into strings, helping readers better understand and apply this function.
1. What is GROUP_CONCAT()
GROUP_CONCAT() is an aggregate function provided by the MySQL database, which is used to concatenate grouped data into strings in a specified order. It can combine multiple lines of data into a single string, optionally adding separators.
2. Use GROUP_CONCAT()
Using the GROUP_CONCAT() function is very simple, just use it in the SELECT statement and specify the columns to be concatenated. Here is an example:
SELECT department, GROUP_CONCAT(employee_name ORDER BY hire_date SEPARATOR ', ') AS employee_list FROM employees GROUP BY department;
In the above example, we group by department from the "employees" table, and use the GROUP_CONCAT() function to sort the employee names under each department according to the date of entry, and use commas as delimiters for splicing, and the splicing results as a new The columns of "employee_list" are returned.
3. Output the result
Next, let us show the actual effect of the GROUP_CONCAT() function through a table of output results:
| Department | Employee List |
|---|---|
| HR | John Smith, Lisa Johnson, David Lee |
| Sales | Sarah Brown, Tom Wilson, Jessica Taylor |
In the above example, we concatenate employee names according to departments and use commas as separators to get a list of employees corresponding to each department.
4. Summary
Through the GROUP_CONCAT() function, we can conveniently splice the grouped data together in string form. This is very useful in scenarios such as generating reports, merging data, etc. This article introduces the concept and usage of the GROUP_CONCAT() function, and shows readers the specific operation steps and effects through examples and output results.
Hope this article helps you understand and apply the GROUP_CONCAT() function!