How Can I Return NULL Instead of an Error When a Database Query Finds No Matching Record?

Handling Null Values in Database Records

When querying a database, it's common to encounter situations where records with specific criteria may not exist. By default, most databases return an error if no matching record is found. However, it's often desirable to return a null value instead.

Consider this example query:

SELECT idnumber FROM dbo.database WHERE number = '9823474'

If the specified number doesn't exist in the table, the query fails. To return null instead, we can utilize a sub-query as follows:

SELECT (SELECT idnumber FROM dbo.database WHERE number = '9823474') AS idnumber;

This encapsulates the original query within a sub-query, allowing us to treat "no row" as a null value. This technique has been tested and verified in various databases, including PostgreSQL, SQLite, SQL Server, MySQL, Oracle, Firebird, DB2, and SQLite.

In Oracle, the syntax requires selecting from the dummy 1-row table DUAL:

SELECT (SELECT idnumber FROM dbo.database WHERE number = '9823474') AS idnumber FROM DUAL;

In MySQL and Firebird, you can use a similar approach by selecting from RDB$DATABASE or SYSIBM.SYSDUMMY1, respectively.

This solution provides a simple and consistent method for handling null values in database queries, ensuring that your code can gracefully handle both valid and non-existent records.

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