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For example, you can use the CASE expression in statements such as SELECT, UPDATE, or DELETE, and in clauses like SELECT, WHERE, HAVING, and ORDDER BY. Oracle CASE expression has two formats: the simple CASE expression and the searched CASE expression. Both formats support an optional ELSE clause.
Script Name Simple SQL CASE example. Description In this simple CASE expression, Oracle Database evaluates the first WHEN and returns the THEN if satisfied. It next considers the next WHEN condition. If none of the when conditions are met the ELSE is taken. Area SQL General. Contributor Mike Hichwa (Oracle) Created Tuesday February 23, 2016.
A WHEN clause can return the result of another CASE expression. This checks if the row is for a genuine result first. If it is, it returns the result of the grading CASE expression. It also has separate CASE expressions to see if a result is for a test exam or student, concatenating their output.
The first thing to note is that CASE expressions are defined in the Expressions chapter of the Oracle SQL Language Reference Manual. This offers our first hint of the power of CASE, because it indicates that we can use it wherever we might use any other expression, in the SELECT, WHERE or ORDER BY clauses for example.
Description PL/SQL offers a CASE statement and CASE expression, which gives you a nice alternative to the traditional IF. The CASE expression is particularly nice, since you can use it inside a statement.
A CASE expression evaluates a list of conditions and returns one of multiple possible result expressions. The result of a CASE expression is a single value whereas the result of a CASE statement is the execution of a sequence of statements.
In a simple CASE expression, Oracle Database searches for the first WHEN... THEN pair for which expr is equal to comparison_expr and returns return_expr. If none of the WHEN... THEN pairs meet this condition, and an ELSE clause exists, then Oracle returns else_expr. Otherwise, Oracle returns null.
