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As mentioned above, here is my contrib/tablefunc patch. It includes
three functions which exercise the tablefunc API.
show_all_settings()
- returns the same information as SHOW ALL, but as a query result
normal_rand(int numvals, float8 mean, float8 stddev, int seed)
- returns a set of normally distributed float8 values
- This routine implements Algorithm P (Polar method for normal
deviates) from Knuth's _The_Art_of_Computer_Programming_, Volume 2,
3rd ed., pages 122-126. Knuth cites his source as "The polar
method", G. E. P. Box, M. E. Muller, and G. Marsaglia,
_Annals_Math,_Stat._ 29 (1958), 610-611.
crosstabN(text sql)
- returns a set of row_name plus N category value columns
- crosstab2(), crosstab3(), and crosstab4() are defined for you,
but you can create additional crosstab functions per directions
in the README.
Joe Conway
This commit is contained in:
Bruce Momjian
272
contrib/tablefunc/README.tablefunc
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contrib/tablefunc/README.tablefunc
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/*
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* tablefunc
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*
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* Sample to demonstrate C functions which return setof scalar
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* and setof composite.
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* Joe Conway <mail@joeconway.com>
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*
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* Copyright 2002 by PostgreSQL Global Development Group
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*
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* Permission to use, copy, modify, and distribute this software and its
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* documentation for any purpose, without fee, and without a written agreement
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* is hereby granted, provided that the above copyright notice and this
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* paragraph and the following two paragraphs appear in all copies.
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*
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* IN NO EVENT SHALL THE AUTHORS OR DISTRIBUTORS BE LIABLE TO ANY PARTY FOR
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* DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING
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* LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS
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* DOCUMENTATION, EVEN IF THE AUTHOR OR DISTRIBUTORS HAVE BEEN ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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* THE AUTHORS AND DISTRIBUTORS SPECIFICALLY DISCLAIM ANY WARRANTIES,
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* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
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* AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS
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* ON AN "AS IS" BASIS, AND THE AUTHOR AND DISTRIBUTORS HAS NO OBLIGATIONS TO
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* PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
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*
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*/
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Version 0.1 (20 July, 2002):
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First release
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Release Notes:
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Version 0.1
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- initial release
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Installation:
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Place these files in a directory called 'tablefunc' under 'contrib' in the
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PostgreSQL source tree. Then run:
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make
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make install
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You can use tablefunc.sql to create the functions in your database of choice, e.g.
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psql -U postgres template1 < tablefunc.sql
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installs following functions into database template1:
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show_all_settings()
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- returns the same information as SHOW ALL, but as a query result
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normal_rand(int numvals, float8 mean, float8 stddev, int seed)
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- returns a set of normally distributed float8 values
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crosstabN(text sql)
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- returns a set of row_name plus N category value columns
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- crosstab2(), crosstab3(), and crosstab4() are defined for you,
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but you can create additional crosstab functions per the instructions
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in the documentation below.
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Documentation
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==================================================================
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Name
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show_all_settings() - returns the same information as SHOW ALL,
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but as a query result.
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Synopsis
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show_all_settings()
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Inputs
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none
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Outputs
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Returns setof tablefunc_config_settings which is defined by:
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CREATE VIEW tablefunc_config_settings AS
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SELECT
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''::TEXT AS name,
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''::TEXT AS setting;
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Example usage
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test=# select * from show_all_settings();
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name | setting
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-------------------------------+---------------------------------------
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australian_timezones | off
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authentication_timeout | 60
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checkpoint_segments | 3
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.
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.
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.
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wal_debug | 0
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wal_files | 0
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wal_sync_method | fdatasync
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(94 rows)
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==================================================================
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Name
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normal_rand(int, float8, float8, int) - returns a set of normally
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distributed float8 values
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Synopsis
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normal_rand(int numvals, float8 mean, float8 stddev, int seed)
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Inputs
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numvals
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the number of random values to be returned from the function
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mean
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the mean of the normal distribution of values
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stddev
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the standard deviation of the normal distribution of values
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seed
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a seed value for the pseudo-random number generator
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Outputs
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Returns setof float8, where the returned set of random values are normally
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distributed (Gaussian distribution)
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Example usage
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test=# SELECT * FROM
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test=# normal_rand(1000, 5, 3, EXTRACT(SECONDS FROM CURRENT_TIME(0))::int);
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normal_rand
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----------------------
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1.56556322244898
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9.10040991424657
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5.36957140345079
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-0.369151492880995
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0.283600703686639
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.
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.
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.
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4.82992125404908
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9.71308014517282
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2.49639286969028
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(1000 rows)
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Returns 1000 values with a mean of 5 and a standard deviation of 3.
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==================================================================
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Name
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crosstabN(text) - returns a set of row_name plus N category value columns
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Synopsis
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crosstabN(text sql)
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Inputs
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sql
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A SQL statement which produces the source set of data. The SQL statement
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must return one row_name column, one category column, and one value
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column.
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e.g. provided sql must produce a set something like:
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row_name cat value
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----------+-------+-------
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row1 cat1 val1
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row1 cat2 val2
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row1 cat3 val3
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row1 cat4 val4
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row2 cat1 val5
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row2 cat2 val6
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row2 cat3 val7
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row2 cat4 val8
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Outputs
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Returns setof tablefunc_crosstab_N, which is defined by:
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CREATE VIEW tablefunc_crosstab_N AS
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SELECT
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''::TEXT AS row_name,
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''::TEXT AS category_1,
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''::TEXT AS category_2,
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.
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.
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.
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''::TEXT AS category_N;
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for the default installed functions, where N is 2, 3, or 4.
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e.g. the provided crosstab2 function produces a set something like:
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<== values columns ==>
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row_name category_1 category_2
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---------+------------+------------
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row1 val1 val2
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row2 val5 val6
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Notes
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1. The sql result must be ordered by 1,2.
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2. The number of values columns depends on the tuple description
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of the function's declared return type.
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3. Missing values (i.e. not enough adjacent rows of same row_name to
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fill the number of result values columns) are filled in with nulls.
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4. Extra values (i.e. too many adjacent rows of same row_name to fill
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the number of result values columns) are skipped.
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5. Rows with all nulls in the values columns are skipped.
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6. The installed defaults are for illustration purposes. You
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can create your own return types and functions based on the
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crosstab() function of the installed library.
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The return type must have a first column that matches the data
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type of the sql set used as its source. The subsequent category
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columns must have the same data type as the value column of the
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sql result set.
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Create a VIEW to define your return type, similar to the VIEWS
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in the provided installation script. Then define a unique function
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name accepting one text parameter and returning setof your_view_name.
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For example, if your source data produces row_names that are TEXT,
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and values that are FLOAT8, and you want 5 category columns:
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CREATE VIEW my_crosstab_float8_5_cols AS
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SELECT
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''::TEXT AS row_name,
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0::FLOAT8 AS category_1,
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0::FLOAT8 AS category_2,
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0::FLOAT8 AS category_3,
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0::FLOAT8 AS category_4,
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0::FLOAT8 AS category_5;
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CREATE OR REPLACE FUNCTION crosstab_float8_5_cols(text)
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RETURNS setof my_crosstab_float8_5_cols
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AS '$libdir/tablefunc','crosstab' LANGUAGE 'c' STABLE STRICT;
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Example usage
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create table ct(id serial, rowclass text, rowid text, attribute text, value text);
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insert into ct(rowclass, rowid, attribute, value) values('group1','test1','att1','val1');
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insert into ct(rowclass, rowid, attribute, value) values('group1','test1','att2','val2');
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insert into ct(rowclass, rowid, attribute, value) values('group1','test1','att3','val3');
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insert into ct(rowclass, rowid, attribute, value) values('group1','test1','att4','val4');
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insert into ct(rowclass, rowid, attribute, value) values('group1','test2','att1','val5');
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insert into ct(rowclass, rowid, attribute, value) values('group1','test2','att2','val6');
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insert into ct(rowclass, rowid, attribute, value) values('group1','test2','att3','val7');
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insert into ct(rowclass, rowid, attribute, value) values('group1','test2','att4','val8');
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select * from crosstab3(
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'select rowid, attribute, value
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from ct
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where rowclass = ''group1''
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and (attribute = ''att2'' or attribute = ''att3'') order by 1,2;');
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row_name | category_1 | category_2 | category_3
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----------+------------+------------+------------
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test1 | val2 | val3 |
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test2 | val6 | val7 |
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(2 rows)
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==================================================================
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-- Joe Conway
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