How to Split Comma-Separated Values into Rows in MySQL?

Transforming Comma-Separated Data in MySQL

This guide explains how to efficiently convert comma-separated values within a MySQL column into individual rows. We'll leverage MySQL functions and a clever technique:

1. Creating a Number Sequence: First, generate a temporary table (or use an existing one) containing a sequence of integers. This sequence should be larger than the maximum number of comma-separated values in your target column. This sequence will act as an index for extracting individual values.

2. Leveraging SUBSTRING_INDEX: The SUBSTRING_INDEX function is key here. It extracts substrings based on a delimiter and a specified occurrence. We'll use it twice, in conjunction with the number sequence, to isolate each value.

Here's an example illustrating this approach:

SELECT SUBSTRING_INDEX(SUBSTRING_INDEX(t.values, ',', n.n), ',', -1) AS value
FROM table1 t
CROSS JOIN (SELECT a.N + b.N * 10 + c.N * 100 AS n FROM
    (SELECT 0 AS N UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) a
    ,(SELECT 0 AS N UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) b
    ,(SELECT 0 AS N UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) c
) n
WHERE n.n <= LENGTH(t.values) - LENGTH(REPLACE(t.values, ',', '')) + 1;

Explanation:

• The nested SELECT statement creates a number sequence (adjust as needed for your data).
• CROSS JOIN combines this sequence with your table (table1).
• SUBSTRING_INDEX(t.values, ',', n.n) extracts the substring up to the nth comma.
• SUBSTRING_INDEX(..., ',', -1) then extracts the value from the previous result to the end of the string.
• WHERE clause ensures we only process values within the bounds of the comma-separated string. The condition LENGTH(t.values) - LENGTH(REPLACE(t.values, ',', '')) 1 dynamically calculates the number of values.

This method effectively splits your comma-separated values into individual rows, providing a clean and efficient solution for data manipulation in MySQL. Remember to replace table1 and values with your actual table and column names.

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