sql select default value if no rows returned

In SQL, when querying a database, you might encounter situations where no rows match the criteria specified in your SELECT statement. In such cases, the query returns an empty result set. However, there may be scenarios where you’d want a default value returned instead of an empty set, for example, in reporting or data analytics. One way to accomplish this is through the use of the SQL COALESCE function or the CASE statement in combination with subqueries or joins. For instance, you could write a query like SELECT COALESCE((SELECT column_name FROM table_name WHERE condition), ‘default_value’). What this does is attempt to retrieve ‘column_name’ from ‘table_name’ based on the ‘condition’. If no rows are returned, the COALESCE function ensures that ‘default_value’ is returned instead. Another approach is using a UNION to attach a default row that gets selected only when the main query returns no results; however, this may involve more complex logic and could be less efficient. The key idea is to build your SQL query in such a way that it anticipates the possibility of no rows being returned and specifies an alternative default value in those cases. This ensures that your applications or reports that rely on the SQL query will have consistent outputs, even when the data is not available in the expected format.