![]() Recursive WITH or Hierarchical queries, is a form of CTE where a CTE can reference to itself, i.e., a WITH query can refer to its own output, hence the name recursive. This allows you to perform several different operations in the same query. ![]() You can use data-modifying statements (INSERT, UPDATE or DELETE) in WITH. The name_for_summary_data can be the same as an existing table name and will take precedence. Where name_for_summary_data is the name given to the WITH clause. The guide has some other good tips on how to speed up the process, like removing indexes and foreign keys before loading the data (and adding them back afterwards). The basic syntax of WITH query is as follows − 12 Answers Sorted by: 292 PostgreSQL has a guide on how to best populate a database initially, and they suggest using the COPY command for bulk loading rows. The WITH clause must be defined before it is used in the query. It computes the aggregation once and allows us to reference it by its name (may be multiple times) in the queries. ![]() It is equally helpful in place of temporary tables. Each auxiliary statement in a WITH clause can be a SELECT, INSERT, UPDATE, or DELETE and the WITH clause itself is attached to a primary statement that can be a SELECT, INSERT, UPDATE, DELETE, or MERGE. The WITH query being CTE query, is particularly useful when subquery is executed multiple times. If the INSERT command contains a RETURNING clause, the result will be similar to that of a SELECT statement containing the columns and values defined in the RETURNING list, computed over the row(s) inserted or updated by the command. These statements often referred to as Common Table Expressions or CTEs, can be thought of as defining temporary tables that exist just for one query. It helps in breaking down complicated and large queries into simpler forms, which are easily readable. One can insert one or more rows specified by value expressions, or zero or more rows resulting from a query. In PostgreSQL, the WITH query provides a way to write auxiliary statements for use in a larger query.
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