The recursive member query executes until there’s no record produced by a given iteration, which happens when the value of i becomes 5. The first time the recursive member is executed, the i and consecutive_sum columns have the value of 0 because those were provided by the anchor member, and the record produced by the first recursive iteration is going to be:įor the second iteration of the recursive member, the value produced for i is going to be 1 + 1, and consecutive_sum is going to be (1 + 1) + 1: Lines 4 to 6 define the recursive member, which is an SQL query that provides the records to be added on each iteration.īecause the FROM clause of the recursive member is the Recursive CTE itself, it means we are going to pass the previously generated record on each iteration. In fact, the Recursive CTE result set is built iteratively, similarly to a while loop in a procedural programming language: The UNION ALL operator is used because we need to simulate the recursion using relational algebra. The anchor member is responsible for producing the first record of the Recursive CTE result set: The second line defines the anchor member of the Recursive CTE: The very first line defines the name of the Recursive CTE and the columns of this temporary result set, i and consecutive_sum in our case: When running the Recursive CTE query above, we get the following result set: If you’re using Oracle or SQL Server, notice that the RECURSIVE keyword is not supported, so you need to omit it when writing a Recursive CTE query. WITH RECURSIVE consecutive_number_sum (i, consecutive_sum) AS ( To see how Recursive WITH queries work, consider the following example that calculates the consecutive sums until a given threshold: While we can use the WITH clause as an alternative to Derived Tables or Inline Views, the WITH clause allows us to build a result set in a recursive fashion. In SQL, the WITH clause allows us to define a Common Table Expression or CTE to assign an alias to a transient query result set. In this article, we are going to see how SQL Recursive WITH CTE (Common Table Expression) queries work and how we can apply them for processing hierarchical data models. So, enjoy spending your time on the things you love rather than fixing performance issues in your production system on a Saturday night! Well, Hypersistence Optimizer is that tool!Īnd it works with Spring Boot, Spring Framework, Jakarta EE, Java EE, Quarkus, or Play Framework. Follow having a tool that can automatically detect JPA and Hibernate performance issues.

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