How to Concatenate Multiple Rows into a Single Row in Oracle Without Stored Procedures?

Concatenating Multiple Rows into a Single Row in Oracle Without Stored Procedures

The issue at hand seeks a method in Oracle to concatenate multiple rows into one without resorting to stored procedures. The given data set consists of question_id and element_id columns with duplicate question_id values. The desired result is to merge the element_id values associated with the same question_id into a single row.

Achieving this can be accomplished using the LISTAGG clause, introduced in Oracle 11gR2. Here's the syntax:

SELECT question_id,
       LISTAGG(element_id, ',') WITHIN GROUP (ORDER BY element_id)
FROM YOUR_TABLE
GROUP BY question_id;

This clause concatenates the element_id values for each question_id, separated by the specified delimiter (a comma in this case). Note that the WITHIN GROUP clause ensures that the values are ordered before concatenation.

For Oracle versions 12cR2 and later, the ON OVERFLOW TRUNCATE/ERROR clauses can be used to handle potential issues with string length limitations:

SELECT question_id,
       LISTAGG(element_id, ',') WITHIN GROUP (ORDER BY element_id)
       ON OVERFLOW TRUNCATE
FROM YOUR_TABLE
GROUP BY question_id;

or

SELECT question_id,
       LISTAGG(element_id, ',') WITHIN GROUP (ORDER BY element_id)
       ON OVERFLOW ERROR
FROM YOUR_TABLE
GROUP BY question_id;

By adhering to the syntax and using the appropriate options, developers can concatenate multiple rows into a single row without creating stored procedures in Oracle.

The above is the detailed content of How to Concatenate Multiple Rows into a Single Row in Oracle Without Stored Procedures?. For more information, please follow other related articles on the PHP Chinese website!