> For the complete documentation index, see [llms.txt](https://docs.postgresql.tw/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.postgresql.tw/the-sql-language/functions/functions-srf.md). # 9.26. Set Returning Functions \# This section describes functions that possibly return more than one row. The most widely used functions in this class are series generating functions, as detailed in [Table 9.69](#FUNCTIONS-SRF-SERIES) and [Table 9.70](#FUNCTIONS-SRF-SUBSCRIPTS). Other, more specialized set-returning functions are described elsewhere in this manual. See [Section 7.2.1.4](/the-sql-language/queries/queries-table-expressions.md#QUERIES-TABLEFUNCTIONS) for ways to combine multiple set-returning functions. **Table 9.69. Series Generating Functions** |

Function

Description

| | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | |

generate\_series ( start integer, stop integer \[, step integer ] ) → setof integer

generate\_series ( start bigint, stop bigint \[, step bigint ] ) → setof bigint

generate\_series ( start numeric, stop numeric \[, step numeric ] ) → setof numeric

Generates a series of values from start to stop, with a step size of step. step defaults to 1.

| |

generate\_series ( start timestamp, stop timestamp, step interval ) → setof timestamp

generate\_series ( start timestamp with time zone, stop timestamp with time zone, step interval \[, timezone text ] ) → setof timestamp with time zone

Generates a series of values from start to stop, with a step size of step. In the timezone-aware form, times of day and daylight-savings adjustments are computed according to the time zone named by the timezone argument, or the current TimeZone setting if that is omitted.

|
When *`step`* is positive, zero rows are returned if *`start`* is greater than *`stop`*. Conversely, when *`step`* is negative, zero rows are returned if *`start`* is less than *`stop`*. Zero rows are also returned if any input is `NULL`. It is an error for *`step`* to be zero. Some examples follow: ``` SELECT * FROM generate_series(2,4); generate_series ----------------- 2 3 4 (3 rows) SELECT * FROM generate_series(5,1,-2); generate_series ----------------- 5 3 1 (3 rows) SELECT * FROM generate_series(4,3); generate_series ----------------- (0 rows) SELECT generate_series(1.1, 4, 1.3); generate_series ----------------- 1.1 2.4 3.7 (3 rows) -- this example relies on the date-plus-integer operator: SELECT current_date + s.a AS dates FROM generate_series(0,14,7) AS s(a); dates ------------ 2004-02-05 2004-02-12 2004-02-19 (3 rows) SELECT * FROM generate_series('2008-03-01 00:00'::timestamp, '2008-03-04 12:00', '10 hours'); generate_series --------------------- 2008-03-01 00:00:00 2008-03-01 10:00:00 2008-03-01 20:00:00 2008-03-02 06:00:00 2008-03-02 16:00:00 2008-03-03 02:00:00 2008-03-03 12:00:00 2008-03-03 22:00:00 2008-03-04 08:00:00 (9 rows) -- this example assumes that TimeZone is set to UTC; note the DST transition: SELECT * FROM generate_series('2001-10-22 00:00 -04:00'::timestamptz, '2001-11-01 00:00 -05:00'::timestamptz, '1 day'::interval, 'America/New_York'); generate_series ------------------------ 2001-10-22 04:00:00+00 2001-10-23 04:00:00+00 2001-10-24 04:00:00+00 2001-10-25 04:00:00+00 2001-10-26 04:00:00+00 2001-10-27 04:00:00+00 2001-10-28 04:00:00+00 2001-10-29 05:00:00+00 2001-10-30 05:00:00+00 2001-10-31 05:00:00+00 2001-11-01 05:00:00+00 (11 rows) ``` **Table 9.70. Subscript Generating Functions** |

Function

Description

generate\_subscripts ( array anyarray, dim integer ) → setof integer

Generates a series comprising the valid subscripts of the dim'th dimension of the given array.

| |

generate\_subscripts ( array anyarray, dim integer, reverse boolean ) → setof integer

Generates a series comprising the valid subscripts of the dim'th dimension of the given array. When reverse is true, returns the series in reverse order.

|
`generate_subscripts` is a convenience function that generates the set of valid subscripts for the specified dimension of the given array. Zero rows are returned for arrays that do not have the requested dimension, or if any input is `NULL`. Some examples follow: ``` -- basic usage: SELECT generate_subscripts('{NULL,1,NULL,2}'::int[], 1) AS s; s --- 1 2 3 4 (4 rows) -- presenting an array, the subscript and the subscripted -- value requires a subquery: SELECT * FROM arrays; a -------------------- {-1,-2} {100,200,300} (2 rows) SELECT a AS array, s AS subscript, a[s] AS value FROM (SELECT generate_subscripts(a, 1) AS s, a FROM arrays) foo; array | subscript | value ---------------+-----------+------- {-1,-2} | 1 | -1 {-1,-2} | 2 | -2 {100,200,300} | 1 | 100 {100,200,300} | 2 | 200 {100,200,300} | 3 | 300 (5 rows) -- unnest a 2D array: CREATE OR REPLACE FUNCTION unnest2(anyarray) RETURNS SETOF anyelement AS $$ select $1[i][j] from generate_subscripts($1,1) g1(i), generate_subscripts($1,2) g2(j); $$ LANGUAGE sql IMMUTABLE; CREATE FUNCTION SELECT * FROM unnest2(ARRAY[[1,2],[3,4]]); unnest2 --------- 1 2 3 4 (4 rows) ``` When a function in the `FROM` clause is suffixed by `WITH ORDINALITY`, a `bigint` column is appended to the function's output column(s), which starts from 1 and increments by 1 for each row of the function's output. This is most useful in the case of set returning functions such as `unnest()`. ``` -- set returning function WITH ORDINALITY: SELECT * FROM pg_ls_dir('.') WITH ORDINALITY AS t(ls,n); ls | n -----------------+---- pg_serial | 1 pg_twophase | 2 postmaster.opts | 3 pg_notify | 4 postgresql.conf | 5 pg_tblspc | 6 logfile | 7 base | 8 postmaster.pid | 9 pg_ident.conf | 10 global | 11 pg_xact | 12 pg_snapshots | 13 pg_multixact | 14 PG_VERSION | 15 pg_wal | 16 pg_hba.conf | 17 pg_stat_tmp | 18 pg_subtrans | 19 (19 rows) ``` *** 原文：[PostgreSQL 18.6 Documentation](https://www.postgresql.org/docs/18/functions-srf.html)（英文原文，待翻譯） --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://docs.postgresql.tw/the-sql-language/functions/functions-srf.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.