How to resolve the issue of invalid usage with oracle wm_concat?

After version 11g, Oracle removed the wm_concat function, so it can no longer be used directly in newer versions.

If you need to concatenate multiple lines of data into a single string, you can achieve this by using the LISTAGG function. The syntax of the LISTAGG function is as follows:

LISTAGG(column_name, separator) WITHIN GROUP (ORDER BY column_name)

In this case, column_name is the name of the column to be joined, and separator is the delimiter for the join. If you need to sort by a specific column, you can use the WITHIN GROUP (ORDER BY column_name) clause. Here is an example using the LISTAGG function:

SELECT department_id, LISTAGG(employee_name, ',') WITHIN GROUP (ORDER BY employee_name)
FROM employees
GROUP BY department_id;

If you are using an older version of Oracle, you can also consider using alternative methods to achieve string concatenation, such as using the XMLAGG function or custom functions.