![]() Then all rows generated by both the initial-select and the Repeated rows are discarded before beingĪdded to the queue even if the repeated rows have already been extractedįrom the queue by the recursion step. ![]() Recursive-select, then only add rows to the queue ifīeen previously added to the queue. If a UNION operator connects the initial-select with the The basic procedure above may modified by the following additional rules: Row in the recursive table and run the recursive-select, Pretend that the single row just extracted is the only.Insert that single row into the recursive table.Run the initial-select and add the results to a queue.The basic algorithm for computing the content of the recursive table SQLite, the recursive-select could only be a single The ability for the recursive-select to be a compound ORDER BY, LIMIT, and/or OFFSET but may not use The recursive-select is allowed to include an The same UNION or UNION ALL operator that separates ![]() The restriction that all elements of that compound must be separated by The recursive-select may also be a compound select with Top-level SELECT statement in the recursive-selectĪnd must not appear anywhere else in either theĪ compound select, but it may not include an ORDER BY, LIMIT, or OFFSET. Table must appear exactly once in the FROM clause of each In the recursive-cte bubble diagram above, the recursive Recursive-select but more than one of each is allowed.Ĭall the table named by the cte-table-name in a recursiveĬommon table expression the "recursive table". To be exactly one initial-select and exactly one Non-recursive SELECT statements and recursive-select means In the diagram above, initial-select means one or more To put it another way, a recursive common table expression must Recursive SELECT statements may not use.The first recursive SELECT from the last non-recursive SELECT statement. If there are two or more recursive SELECT statements, they all mustīe separated from each other using the same operator that separates The recursive SELECT statements must be separated from theĪnd from each other by the UNION or UNION ALL operators.All non-recursive SELECT statements must occur before any.One or more of the SELECT statements in the compound must be.The CTE table (the table named on the left-hand side of the Its FROM clause contains exactly one reference to the One or more of the individual SELECT statements that make up.Separated by compound operators like UNION, UNION ALL, INTERSECT, ![]() The CTE body must be two or more individual SELECT statements The " select-stmt" must be a compound select.A recursive common table expression has the sameīasic syntax as an ordinary common table expression, but with the following The use of RECURSIVE does not forceĬommon table expressions to be recursive.Ī recursive common table expression can be used to write a query that SQL statement easier to read and understand.Ī WITH clause can contain ordinary common table expressions even if Ordinary common tableĮxpressions are useful for factoring out subqueries and making the overall A single WITH clause can specify one or moreĬommon table expressions, some of which are ordinary and some of whichĪn ordinary common table expression works as if it were a view thatĮxists for the duration of a single statement. That is not otherwise available in the SQL language.Īll common table expressions (ordinary and recursive) areĬreated by prepending a WITH clause in front of a SELECT, INSERT, DELETE, Recursive queries of trees and graphs, a capability Provide the ability to do hierarchical or Subqueries out of the main SQL statement. Queries easier to understand by factoring OrdinaryĬommon table expressions are helpful for making There are two kinds ofĬommon table expressions: "ordinary" and "recursive". Only for the duration of a single SQL statement. GROUPS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING RANGE ROWS UNBOUNDED PRECEDING expr PRECEDING CURRENT ROW expr PRECEDING CURRENT ROW expr FOLLOWING expr PRECEDING CURRENT ROW expr FOLLOWING EXCLUDE CURRENT ROW EXCLUDE GROUP EXCLUDE TIES EXCLUDE NO OTHERSĬommon Table Expressions or CTEs act like temporary views that exist
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