If you are a SQL Server user, you may have encountered the need to remove non-numeric characters from a VARCHAR column. This can be a tedious task, especially if the column contains a large number of records. But fear not, as we have discovered the fastest method to achieve this task.
First, let's understand why removing non-numeric characters may be necessary. In many cases, the data stored in a VARCHAR column may contain a mix of numbers and characters. This can be problematic if you need to perform numerical operations on the data, such as sorting or performing calculations. Non-numeric characters can also cause errors when trying to convert the data to a different data type.
So, what is the fastest method to remove these pesky non-numeric characters? The answer lies in the use of the T-SQL function called PATINDEX. This function returns the starting position of a pattern (specified by a regular expression) in a given string. Let's see how we can use this function to our advantage.
Assuming we have a table called "Employee" with a column named "Phone" that contains phone numbers in the format of (xxx) xxx-xxxx, we can use the following query to remove the non-numeric characters and retrieve only the numerical values:
SELECT REPLACE(SUBSTRING(Phone, PATINDEX('%[0-9]%', Phone), LEN(Phone)), ' ', '') AS 'Phone Number'
FROM Employee
Let's break down this query to understand how it works. The PATINDEX function is used to find the starting position of the first numeric character in the "Phone" column. This is achieved by using the regular expression '[0-9]' which matches any single digit from 0 to 9. The SUBSTRING function is then used to extract the substring starting from the found position to the end of the string. Finally, the REPLACE function is used to remove any spaces that may exist in the extracted substring.
This method not only removes non-numeric characters but also takes care of any spaces that may be present in the original string. This is important because spaces can also cause errors when trying to convert the data to a different data type.
But what if you want to remove non-numeric characters from a column that contains a mix of numbers and characters, without the use of a specific pattern? In such cases, we can use the ISNUMERIC function in conjunction with the PATINDEX function. The ISNUMERIC function checks whether a value is numeric or not and returns 1 if the value is numeric and 0 if it is not.
Let's say we have a column called "Salary" that contains values like $50,000 or €75,000. We can use the following query to remove the non-numeric characters and retrieve only the numerical values:
SELECT CAST(REPLACE(SUBSTRING(Salary, PATINDEX('%[0-9]%', Salary), LEN(Salary)), ' ', '') AS NUMERIC) AS 'Salary'
FROM Employee
In this query, the ISNUMERIC function is used to check whether the extracted substring is numeric or not. If it is numeric, it is then converted to the NUMERIC data type using the CAST function. This ensures that all non-numeric characters are removed, and only the numerical values are retrieved.
In conclusion, the fastest method to remove non-numeric characters from a VARCHAR column in SQL Server is by using the PATINDEX function. This method not only removes non-numeric characters but also takes care of any spaces that may be present in the original string. So, next time you face the task of removing non-numeric characters, remember this handy tip and save yourself some time and effort.
