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1 Μαΐ 2018 · If I wanted to write a recursive query that travelled up this family tree, collecting all parents until origin, how should I go about this? Use a hierarchical query and the SYS_CONNECT_BY_PATH( column_name, delimiter ) function:
This articles gives an overview of how to query hierarchical data in Oracle databases using recursive subquery factoring. This functionality was introduced in Oracle 11g Release 2, giving an alternative to the method of performing hierarchical queries from previous versions. Setup; Basic Hierarchical Query; Implement Equivalent of LEVEL
Using recursive with you can choose any columns in your query to mark a "loop". This allows you to stop processing before you get back to the same row. For example, you can cycle on department_id.
If your RDBMS is PostgreSQL, IBM DB2, MS SQL Server, Oracle (only from 11g release 2), or MySQL (only from release 8.0.1) you can use WITH queries, known as Common Table Expressions (CTEs). Generally speaking, they allow you to split complicated queries into a set of simpler ones which makes a query easier to read.
subquery_factoring_clause, which supports recursive subquery factoring (recursive WITH) and lets you query hierarchical data. This feature is more powerful than CONNECT BY in that it provides depth-first search and breadth-first search, and supports multiple recursive branches.
This articles gives an overview of how to query hierarchical data in Oracle databases using SQL. Setup; Basic Hierarchical Query; Cyclic Hierarchical Query; Related articles. Hierarchical Queries in Oracle (CONNECT BY) Hierarchical Queries in Oracle (Recursive WITH Clause) Recursive Subquery Factoring : Hierarchical Queries Using Recursive WITH ...
The WITH clause, or subquery factoring clause, is part of the SQL-99 standard and was added into the Oracle SQL syntax in Oracle 9.2. The WITH clause may be processed as an inline view or resolved as a temporary table.
