How to Reliably Split Comma-Delimited Values into Oracle Table Columns?

Efficiently Parsing Comma-Separated Values in Oracle Tables

Handling large datasets with comma-separated values (CSV) often requires splitting these values into individual columns within an Oracle table for streamlined data analysis and manipulation. While regular expressions offer a solution via the REGEXP_SUBSTR function, a common approach using the expression [^,] can be unreliable.

This is especially true when dealing with CSV data containing null or empty values. To ensure accurate extraction of elements, regardless of nulls or empty strings, a more robust regular expression is necessary. The following expression is recommended:

(.*?)(,|$)

This expression utilizes capture groups to precisely identify the desired element, including any leading or trailing commas. By specifying the capture group index (1) within REGEXP_SUBSTR, you can reliably retrieve the element's value, correctly handling both populated and null values.

Consider this illustrative query:

SELECT
  ROW_NUM,
  REGEXP_SUBSTR(VAL, '(.*?)(,|$)', 1, 1, NULL, 1) AS VAL1,
  REGEXP_SUBSTR(VAL, '(.*?)(,|$)', 1, 2, NULL, 1) AS VAL2
FROM (
  SELECT
    ROWNUM AS ROW_NUM,
    '1.25, 3.87, 2' AS VAL
  FROM dual
  UNION ALL
  SELECT
    ROWNUM,
    '5, 4, 3.3'
  FROM dual
)

This query demonstrates splitting the "VAL" column's comma-separated values into two new columns, "VAL1" and "VAL2," while maintaining data integrity even with null or empty entries. The output clearly shows the separated values. Note the use of ROWNUM and UNION ALL to create sample data, a more standard approach than the original example.

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