How Can I Efficiently Split Comma-Separated Values into Columns in Oracle?

Oracle Database: Efficiently Parsing Comma-Separated Values into Columns

This article tackles a frequent challenge in Oracle: extracting individual values from comma-separated strings (CSV) into distinct columns. Manually processing numerous values (e.g., 255) is impractical; however, Oracle offers efficient solutions.

One effective method employs the REGEXP_SUBSTR function, enabling string splitting using regular expressions. The regular expression's structure is critical for accurate results.

Consider this data:

<code>ROW | VAL
----------- 
1    | 1.25, 3.87, 2, ... 
2    | 5, 4, 3.3, ....</code>

To separate these values into individual columns, we can use this REGEXP_SUBSTR expression:

regexp_substr('1,2,3,,5,6', '(.*?)(,|$)', 1, 5, NULL, 1)

This expression is designed to:

• Locate the 5th occurrence of any character sequence (.) zero or more times (*), followed by a comma (,) or the end of the string ($).
• Extract the first captured group (the data itself, excluding the comma or end-of-string).

This improved expression handles null elements gracefully, preventing them from disrupting the extraction of subsequent values.

For increased reusability, complex regular expressions can be encapsulated within custom functions, as illustrated in this forum discussion: https://www.php.cn/link/ae2cd9938873f32a93b6c858bf62f26b.

In summary, combining REGEXP_SUBSTR with well-crafted regular expressions provides a reliable method for parsing comma-separated values in Oracle, even when dealing with null or missing values.

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