


How Can I Extract Numbers from Strings Using a SQL User-Defined Function?
Extracting Numeric Data from Strings in SQL Using a User-Defined Function
This guide demonstrates how to create a SQL user-defined function (UDF) to efficiently extract only numeric characters from a string. This is a common task in data cleaning and manipulation.
Creating the UDF:
The following SQL code defines a UDF named dbo.udf_GetNumeric
that takes a string as input and returns the extracted numeric portion:
CREATE FUNCTION dbo.udf_GetNumeric ( @strAlphaNumeric VARCHAR(256) ) RETURNS VARCHAR(256) AS BEGIN DECLARE @intAlpha INT SET @intAlpha = PATINDEX('%[^0-9]%', @strAlphaNumeric) BEGIN WHILE @intAlpha > 0 BEGIN SET @strAlphaNumeric = STUFF(@strAlphaNumeric, @intAlpha, 1, '' ) SET @intAlpha = PATINDEX('%[^0-9]%', @strAlphaNumeric ) END END RETURN ISNULL(TRIM(@strAlphaNumeric), '0') END
Applying the UDF:
Once the UDF is created, use the following SELECT statement to apply it to a column in your table:
SELECT dbo.udf_GetNumeric(column_name) AS ExtractedNumber FROM table_name;
Replace column_name
with the actual name of the column containing the strings and table_name
with your table's name. The result will be a new column, ExtractedNumber
, containing only the numeric values.
Illustrative Example:
Consider this sample data:
String 1 | String 2 | String 3 |
---|---|---|
003Preliminary Examination Plan | Coordination005 | Balance1000sheet |
After applying the UDF, the output will be:
String 1 | String 2 | String 3 |
---|---|---|
003 | 005 | 1000 |
Function Explanation:
The dbo.udf_GetNumeric
function uses PATINDEX
to locate the first non-numeric character. The STUFF
function then removes that character. This process repeats until all non-numeric characters are eliminated, leaving only the numbers. The ISNULL
and TRIM
functions handle potential null values and leading/trailing spaces.
Further Enhancements (Future Update): A more detailed explanation and potential improvements to this function will be added in a future update.
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