How Can I Split Comma-Separated Values in SQL into Separate Rows?

Split comma separated row values ​​in SQL

In database management, it is common to encounter data stored as comma-separated values ​​(CSV). However, for some analysis or reporting purposes, you may want to split these CSVs into separate rows. In this article, we'll explore a SQL-based approach to performing this split operation.

The solution involves utilizing the SUBSTRING_INDEX() function in MySQL. This function allows us to extract a substring from a specified string based on the delimiter character. We also use a cross join with a count table to generate a series of numbers that are used as row indices for splitting the CSV.

The following is the SQL query:

<code class="language-sql">SELECT SUBSTRING_INDEX(SUBSTRING_INDEX(t.values, ',', n.n), ',', -1) value
FROM table1 t CROSS JOIN 
(
   SELECT a.N + b.N * 10 + 1 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
    ORDER BY n
) n
WHERE n.n <= LENGTH(t.values) - LENGTH(REPLACE(t.values, ',', '')) + 1;</code>

This query effectively splits the CSV values ​​of the table1 column in the values table and creates a new row for each value. Count tables allow splitting multiple values ​​in a single row.

Example data and output:

Consider the following data from the table1 table:

values

somethingA,somethingB,somethingC

somethingElseA, somethingElseB

Applying the query to this data will produce the following output:

value

somethingA

somethingB

somethingC

somethingElseA

somethingElseB

By leveraging this technology, data stored in CSV format can be conveniently split into individual rows, allowing for further analysis or processing.

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