casewhen

CASE WHEN is a conditional expression used in SQL and other database query languages. It allows for the creation of an if-then-else logic within a query. This means that based on specified conditions, different values can be returned.

The basic syntax of a CASE WHEN statement involves the keyword CASE, followed by one or more WHEN clauses, each with a condition and a corresponding result. Optionally, an ELSE clause can be included to specify a default result if none of the WHEN conditions are met. Finally, the statement is terminated with the END keyword.

For example, a CASE WHEN statement could be used to categorize sales data. If a sale amount is greater than 1000, it might be labeled "High Value". If it's between 500 and 1000, it could be "Medium Value". Otherwise, it would be "Low Value". This allows for more dynamic and insightful data analysis directly within the database.

CASE WHEN expressions are highly versatile and can be used in SELECT statements, WHERE clauses, ORDER BY clauses, and even within aggregate functions. They are a fundamental tool for data manipulation and conditional logic in relational databases.