![]() ![]() The supplied column name list specifies the row key that is to be used for keeping track of visited rows. ![]() The optional SEARCH clause computes a search sequence column that can be used for ordering the results of a recursive query in either breadth-first or depth-first order. It applies to all queries in the WITH clause, though it has no effect on queries that do not use recursion or forward references. When there are multiple queries in the WITH clause, RECURSIVE should be written only once, immediately after WITH. (However, circular references, or mutual recursion, are not implemented.) Without RECURSIVE, WITH queries can only reference sibling WITH queries that are earlier in the WITH list. See Section 7.8 for an example.Īnother effect of RECURSIVE is that WITH queries need not be ordered: a query can reference another one that is later in the list. Recursive data-modifying statements are not supported, but you can use the results of a recursive SELECT query in a data-modifying statement. Only one recursive self-reference is permitted per query. ![]() ![]() Where the recursive self-reference must appear on the right-hand side of the UNION. Such a subquery must have the form non_recursive_term UNION recursive_term If RECURSIVE is specified, it allows a SELECT subquery to reference itself by name. Optionally, a list of column names can be specified if this is omitted, the column names are inferred from the subquery. If RETURNING is omitted, the statement is still executed, but it produces no output so it cannot be referenced as a table by the primary query.Ī name (without schema qualification) must be specified for each WITH query. It is the output of RETURNING, not the underlying table that the statement modifies, that forms the temporary table that is read by the primary query. When writing a data-modifying statement ( INSERT, UPDATE or DELETE) in WITH, it is usual to include a RETURNING clause. Each subquery can be a SELECT, TABLE, VALUES, INSERT, UPDATE or DELETE statement. The subqueries effectively act as temporary tables or views for the duration of the primary query. The WITH clause allows you to specify one or more subqueries that can be referenced by name in the primary query. The use of FOR NO KEY UPDATE, FOR UPDATE, FOR SHARE or FOR KEY SHARE requires UPDATE privilege as well (for at least one column of each table so selected). You must have SELECT privilege on each column used in a SELECT command. If FOR UPDATE, FOR NO KEY UPDATE, FOR SHARE or FOR KEY SHARE is specified, the SELECT statement locks the selected rows against concurrent updates. If the LIMIT (or FETCH FIRST) or OFFSET clause is specified, the SELECT statement only returns a subset of the result rows. If ORDER BY is not given, the rows are returned in whatever order the system finds fastest to produce. If the ORDER BY clause is specified, the returned rows are sorted in the specified order. (See UNION Clause, INTERSECT Clause, and EXCEPT Clause below.) Notice that DISTINCT is the default behavior here, even though ALL is the default for SELECT itself. The noise word DISTINCT can be added to explicitly specify eliminating duplicate rows. In all three cases, duplicate rows are eliminated unless ALL is specified. The EXCEPT operator returns the rows that are in the first result set but not in the second. The INTERSECT operator returns all rows that are strictly in both result sets. The UNION operator returns all rows that are in one or both of the result sets. Using the operators UNION, INTERSECT, and EXCEPT, the output of more than one SELECT statement can be combined to form a single result set. SELECT ALL (the default) will return all candidate rows, including duplicates. SELECT DISTINCT ON eliminates rows that match on all the specified expressions. SELECT DISTINCT eliminates duplicate rows from the result. The actual output rows are computed using the SELECT output expressions for each selected row or row group. (See GROUP BY Clause and HAVING Clause below.) If the HAVING clause is present, it eliminates groups that do not satisfy the given condition. If the GROUP BY clause is specified, or if there are aggregate function calls, the output is combined into groups of rows that match on one or more values, and the results of aggregate functions are computed. If the WHERE clause is specified, all rows that do not satisfy the condition are eliminated from the output. (Each element in the FROM list is a real or virtual table.) If more than one element is specified in the FROM list, they are cross-joined together. (See WITH Clause below.)Īll elements in the FROM list are computed. A WITH query that is referenced more than once in FROM is computed only once, unless specified otherwise with NOT MATERIALIZED. These effectively serve as temporary tables that can be referenced in the FROM list. SET cycle_mark_col_name USING cycle_path_col_name ]Īll queries in the WITH list are computed. ![]()
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