How to Replace MySQL's GROUP_CONCAT in Oracle?

Oracle's Equivalent to MySQL's GROUP_CONCAT

MySQL's GROUP_CONCAT function efficiently combines multiple rows into a single string. Oracle offers several ways to achieve the same result, depending on your database version.

LISTAGG: The Preferred Method (Oracle 11g and later)

The LISTAGG function is the recommended approach for modern Oracle versions (11g and above). It provides a clean and efficient solution for concatenating values within groups:

<code class="language-sql">SELECT
    col1,
    LISTAGG(col2, ', ') WITHIN GROUP (ORDER BY col2) AS names
FROM table_x
GROUP BY col1</code>

This query groups rows by col1 and concatenates the corresponding col2 values, separated by commas and spaces, ordered by col2.

Custom Function: For Older Oracle Versions (10g and earlier)

For Oracle 10g and earlier versions lacking LISTAGG, a custom function is necessary:

<code class="language-sql">CREATE OR REPLACE FUNCTION get_concatenated_values (input_val IN NUMBER)
  RETURN VARCHAR2
IS
  concatenated_text VARCHAR2(10000) := NULL;
BEGIN
  FOR x IN (SELECT col2 FROM table_name WHERE col1 = input_val) LOOP
    concatenated_text := concatenated_text || ',' || x.col2;
  END LOOP;
  RETURN LTRIM(concatenated_text, ',');
END;
/</code>

Usage:

<code class="language-sql">SELECT col1, get_concatenated_values(col1) FROM table_name;</code>

This function iterates through rows matching the input value and appends the col2 values to a string. The LTRIM function removes the leading comma.

WM_CONCAT: Use with Caution

Some older Oracle versions might include WM_CONCAT. However, it's an unsupported function and its behavior may be inconsistent across versions. Therefore, it's strongly advised to avoid WM_CONCAT and use LISTAGG or a custom function instead:

<code class="language-sql">SELECT col1, WM_CONCAT(col2) FROM table_name GROUP BY col1;</code>

Choose the method appropriate for your Oracle version. LISTAGG is the preferred and most reliable solution for newer versions. For older versions, the custom function provides a robust alternative. Avoid WM_CONCAT unless absolutely necessary and understand its limitations.

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