How to Efficiently Split Strings with Optional Delimiters in T-SQL?

Handling string splitting with or without delimiters in T-SQL

SQL queries often require manipulating strings and extracting specific parts based on delimiters. However, handling situations where delimiters may be missing or optional requires careful planning.

In the given scenario, the task is to split a string column containing names (first name and last name) separated by '/' character. The code initially assumes that all lines contain delimiters, but an error occurs for lines that do not.

In order to deal with this problem efficiently, we can implement the following modifications:

SELECT 
    CASE 
        WHEN CHARINDEX('/', myColumn) = 0 THEN myColumn
        ELSE SUBSTRING(myColumn, 1, CHARINDEX('/', myColumn) - 1)
    END AS FirstName,
    CASE 
        WHEN CHARINDEX('/', myColumn) = 0 THEN NULL
        ELSE SUBSTRING(myColumn, CHARINDEX('/', myColumn) + 1, LEN(myColumn))
    END AS LastName
FROM MyTable;

This modified code uses the CASE statement to check whether the '/' character exists (if it does not exist, CHARINDEX('/') returns 0). If found, the string is split as expected; otherwise, it treats the entire string as the first name and sets the last name to NULL.

By adding this logic, the query becomes robust and can handle rows with and without delimiters, giving the desired output:

FirstName	LastName
John	Smith
Jane	Doe
Steve	NULL
Bob	Johnson

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