Skip to content

G
Gpdb

Greenplum / Gpdb

通知 7
Star 1
Fork 0
G
Gpdb

体验新版 GitCode，发现更多精彩内容 >>

提交 8295c27c 编写于 作者: N Neil Conway
浏览文件
操作

Add documentation for the new "dollar quoting" feature, and update existing 

examples to use dollar quoting when appropriate. Original patch from David
Fetter, additional work and editorializing by Neil Conway.
上级 2871f60f
展开全部 隐藏空白更改
内联 并排
Showing with 371 addition and 253 deletion
doc/src/sgml/plperl.sgml
浏览文件 @ 8295c27c
<!--
$PostgreSQL: pgsql/doc/src/sgml/plperl.sgml,v 2.22 2003/12/14 00:10:32 neilc Exp $
$PostgreSQL: pgsql/doc/src/sgml/plperl.sgml,v 2.23 2004/05/16 23:22:06 neilc Exp $
-->
<chapter id="plperl">
......@@ -46,11 +46,17 @@ $PostgreSQL: pgsql/doc/src/sgml/plperl.sgml,v 2.22 2003/12/14 00:10:32 neilc Exp
<para>
To create a function in the PL/Perl language, use the standard syntax:
<programlisting>
CREATE FUNCTION <replaceable>funcname</replaceable> (<replaceable>argument-types</replaceable>) RETURNS <replaceable>return-type</replaceable> AS '
CREATE FUNCTION <replaceable>funcname</replaceable>
(<replaceable>argument-types</replaceable>) RETURNS <replaceable>return-type</replaceable> AS $$
# PL/Perl function body
' LANGUAGE plperl;
$$ LANGUAGE plperl;
</programlisting>
The body of the function is ordinary Perl code.
The body of the function is ordinary Perl code. Since the body of
the function is treated as a string by
<productname>PostgreSQL</productname>, it can be specified using
dollar quoting (as shown above), or via the usual single quote
syntax (see <xref linkend="sql-syntax-strings"> for more
information).
</para>
<para>
......@@ -65,10 +71,10 @@ CREATE FUNCTION <replaceable>funcname</replaceable> (<replaceable>argument-types
could be defined as:
<programlisting>
CREATE FUNCTION perl_max (integer, integer) RETURNS integer AS '
CREATE FUNCTION perl_max (integer, integer) RETURNS integer AS $$
if ($_[0] > $_[1]) { return $_[0]; }
return $_[1];
' LANGUAGE plperl;
$$ LANGUAGE plperl;
</programlisting>
</para>
......@@ -88,7 +94,7 @@ CREATE FUNCTION perl_max (integer, integer) RETURNS integer AS '
rather than a null value:
<programlisting>
CREATE FUNCTION perl_max (integer, integer) RETURNS integer AS '
CREATE FUNCTION perl_max (integer, integer) RETURNS integer AS $$
my ($a,$b) = @_;
if (! defined $a) {
if (! defined $b) { return undef; }
......@@ -97,7 +103,7 @@ CREATE FUNCTION perl_max (integer, integer) RETURNS integer AS '
if (! defined $b) { return $a; }
if ($a > $b) { return $a; }
return $b;
' LANGUAGE plperl;
$$ LANGUAGE plperl;
</programlisting>
</para>
......@@ -119,10 +125,10 @@ CREATE TABLE employee (
bonus integer
);
CREATE FUNCTION empcomp(employee) RETURNS integer AS '
CREATE FUNCTION empcomp(employee) RETURNS integer AS $$
my ($emp) = @_;
return $emp->{''basesalary''} + $emp->{''bonus''};
' LANGUAGE plperl;
return $emp->{'basesalary'} + $emp->{'bonus'};
$$ LANGUAGE plperl;
SELECT name, empcomp(employee) FROM employee;
</programlisting>
......@@ -136,12 +142,12 @@ SELECT name, empcomp(employee) FROM employee;
<tip>
<para>
Because the function body is passed as an SQL string literal to
<command>CREATE FUNCTION</command>, you have to escape single
quotes and backslashes within your Perl source, typically by
doubling them as shown in the above example. Another possible
approach is to avoid writing single quotes by using Perl's
extended quoting operators (<literal>q[]</literal>,
<literal>qq[]</literal>, <literal>qw[]</literal>).
<command>CREATE FUNCTION</command>, you have to use dollar quoting
or escape single quotes and backslashes within your Perl source,
typically by doubling them. Another possible approach is to avoid
writing single quotes by using Perl's extended quoting operators
(<literal>q[]</literal>, <literal>qq[]</literal>,
<literal>qw[]</literal>).
</para>
</tip>
</sect1>
......@@ -226,11 +232,11 @@ SELECT name, empcomp(employee) FROM employee;
Here is an example of a function that will not work because file
system operations are not allowed for security reasons:
<programlisting>
CREATE FUNCTION badfunc() RETURNS integer AS '
CREATE FUNCTION badfunc() RETURNS integer AS $$
open(TEMP, ">/tmp/badfile");
print TEMP "Gotcha!\n";
return 1;
' LANGUAGE plperl;
$$ LANGUAGE plperl;
</programlisting>
The creation of the function will succeed, but executing it will not.
</para>
......
doc/src/sgml/plpgsql.sgml
浏览文件 @ 8295c27c
此差异已折叠。
doc/src/sgml/plpython.sgml
浏览文件 @ 8295c27c
<!-- $PostgreSQL: pgsql/doc/src/sgml/plpython.sgml,v 1.22 2003/11/29 19:51:37 pgsql Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/plpython.sgml,v 1.23 2004/05/16 23:22:07 neilc Exp $ -->
<chapter id="plpython">
<title>PL/Python - Python Procedural Language</title>
......@@ -230,14 +230,14 @@ rv = plpy.execute(plan, [ "name" ], 5)
<literal>SD</literal> or <literal>GD</literal> (see
<xref linkend="plpython-funcs">). For example:
<programlisting>
CREATE FUNCTION usesavedplan() RETURNS trigger AS '
CREATE FUNCTION usesavedplan() RETURNS trigger AS $$
if SD.has_key("plan"):
plan = SD["plan"]
else:
plan = plpy.prepare("SELECT 1")
SD["plan"] = plan
# rest of function
' LANGUAGE plpythonu;
$$ LANGUAGE plpythonu;
</programlisting>
</para>
</sect1>
......
doc/src/sgml/pltcl.sgml
浏览文件 @ 8295c27c
<!--
$PostgreSQL: pgsql/doc/src/sgml/pltcl.sgml,v 2.29 2004/01/24 23:06:29 tgl Exp $
$PostgreSQL: pgsql/doc/src/sgml/pltcl.sgml,v 2.30 2004/05/16 23:22:07 neilc Exp $
-->
<chapter id="pltcl">
......@@ -77,9 +77,10 @@ $PostgreSQL: pgsql/doc/src/sgml/pltcl.sgml,v 2.29 2004/01/24 23:06:29 tgl Exp $
To create a function in the <application>PL/Tcl</> language, use the standard syntax:
<programlisting>
CREATE FUNCTION <replaceable>funcname</replaceable> (<replaceable>argument-types</replaceable>) RETURNS <replaceable>return-type</replaceable> AS '
CREATE FUNCTION <replaceable>funcname</replaceable>
(<replaceable>argument-types</replaceable>) RETURNS <replaceable>return-type</replaceable> AS $$
# PL/Tcl function body
' LANGUAGE pltcl;
$$ LANGUAGE pltcl;
</programlisting>
<application>PL/TclU</> is the same, except that the language has to be specified as
......@@ -100,10 +101,10 @@ CREATE FUNCTION <replaceable>funcname</replaceable> (<replaceable>argument-types
returning the greater of two integer values could be defined as:
<programlisting>
CREATE FUNCTION tcl_max(integer, integer) RETURNS integer AS '
CREATE FUNCTION tcl_max(integer, integer) RETURNS integer AS $$
if {$1 > $2} {return $1}
return $2
' LANGUAGE pltcl STRICT;
$$ LANGUAGE pltcl STRICT;
</programlisting>
Note the clause <literal>STRICT</>, which saves us from
......@@ -122,7 +123,7 @@ CREATE FUNCTION tcl_max(integer, integer) RETURNS integer AS '
argument, rather than null:
<programlisting>
CREATE FUNCTION tcl_max(integer, integer) RETURNS integer AS '
CREATE FUNCTION tcl_max(integer, integer) RETURNS integer AS $$
if {[argisnull 1]} {
if {[argisnull 2]} { return_null }
return $2
......@@ -130,7 +131,7 @@ CREATE FUNCTION tcl_max(integer, integer) RETURNS integer AS '
if {[argisnull 2]} { return $1 }
if {$1 > $2} {return $1}
return $2
' LANGUAGE pltcl;
$$ LANGUAGE pltcl;
</programlisting>
</para>
......@@ -154,7 +155,7 @@ CREATE TABLE employee (
age integer
);
CREATE FUNCTION overpaid(employee) RETURNS boolean AS '
CREATE FUNCTION overpaid(employee) RETURNS boolean AS $$
if {200000.0 < $1(salary)} {
return "t"
}
......@@ -162,7 +163,7 @@ CREATE FUNCTION overpaid(employee) RETURNS boolean AS '
return "t"
}
return "f"
' LANGUAGE pltcl;
$$ LANGUAGE pltcl;
</programlisting>
</para>
......@@ -359,25 +360,24 @@ spi_exec -array C "SELECT * FROM pg_class" {
Here's an example of a PL/Tcl function using a prepared plan:
<programlisting>
CREATE FUNCTION t1_count(integer, integer) RETURNS integer AS '
CREATE FUNCTION t1_count(integer, integer) RETURNS integer AS $$
if {![ info exists GD(plan) ]} {
# prepare the saved plan on the first call
set GD(plan) [ spi_prepare \\
"SELECT count(*) AS cnt FROM t1 WHERE num &gt;= \\$1 AND num &lt;= \\$2" \\
set GD(plan) [ spi_prepare \
"SELECT count(*) AS cnt FROM t1 WHERE num &gt;= \$1 AND num &lt;= \$2" \
[ list int4 int4 ] ]
}
spi_execp -count 1 $GD(plan) [ list $1 $2 ]
return $cnt
' LANGUAGE pltcl;
$$ LANGUAGE pltcl;
</programlisting>
Note that each backslash that Tcl should see must be doubled when
we type in the function, since the main parser processes
backslashes, too, in <command>CREATE FUNCTION</>. We need backslashes inside
the query string given to <function>spi_prepare</> to ensure that
the <literal>$<replaceable>n</replaceable></> markers will be passed through to
<function>spi_prepare</> as-is, and not
replaced by Tcl variable substitution.
We need backslashes inside the query string given to
<function>spi_prepare</> to ensure that the
<literal>$<replaceable>n</replaceable></> markers will be passed
through to <function>spi_prepare</> as-is, and not replaced by Tcl
variable substitution.
</para>
</listitem>
</varlistentry>
......@@ -425,7 +425,7 @@ SELECT 'doesn't' AS ret
The submitted command should contain
<programlisting>
SELECT 'doesn''t' AS ret
SELECT $q$doesn't$q$ AS ret
</programlisting>
which can be formed in PL/Tcl using
......@@ -611,7 +611,7 @@ SELECT 'doesn''t' AS ret
incremented on every update operation.
<programlisting>
CREATE FUNCTION trigfunc_modcount() RETURNS trigger AS '
CREATE FUNCTION trigfunc_modcount() RETURNS trigger AS $$
switch $TG_op {
INSERT {
set NEW($1) 0
......@@ -625,7 +625,7 @@ CREATE FUNCTION trigfunc_modcount() RETURNS trigger AS '
}
}
return [array get NEW]
' LANGUAGE pltcl;
$$ LANGUAGE pltcl;
CREATE TABLE mytab (num integer, description text, modcnt integer);
......
doc/src/sgml/queries.sgml
浏览文件 @ 8295c27c
<!-- $PostgreSQL: pgsql/doc/src/sgml/queries.sgml,v 1.29 2004/03/03 22:22:24 neilc Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/queries.sgml,v 1.30 2004/05/16 23:22:07 neilc Exp $ -->
<chapter id="queries">
<title>Queries</title>
......@@ -631,9 +631,9 @@ FROM (SELECT * FROM table1) AS alias_name
<programlisting>
CREATE TABLE foo (fooid int, foosubid int, fooname text);
CREATE FUNCTION getfoo(int) RETURNS SETOF foo AS '
CREATE FUNCTION getfoo(int) RETURNS SETOF foo AS $$
SELECT * FROM foo WHERE fooid = $1;
' LANGUAGE SQL;
$$ LANGUAGE SQL;
SELECT * FROM getfoo(1) AS t1;
......
doc/src/sgml/ref/create_function.sgml
浏览文件 @ 8295c27c
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/create_function.sgml,v 1.55 2003/11/29 19:51:38 pgsql Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/create_function.sgml,v 1.56 2004/05/16 23:22:07 neilc Exp $
-->
<refentry id="SQL-CREATEFUNCTION">
......@@ -54,10 +54,10 @@ CREATE [ OR REPLACE ] FUNCTION <replaceable class="parameter">name</replaceable>
To update the definition of an existing function, use
<command>CREATE OR REPLACE FUNCTION</command>. It is not possible
to change the name or argument types of a function this way (if you
tried, you'd just be creating a new, distinct function). Also,
<command>CREATE OR REPLACE FUNCTION</command> will not let you
change the return type of an existing function. To do that, you
must drop and recreate the function.
tried, you would actually be creating a new, distinct function).
Also, <command>CREATE OR REPLACE FUNCTION</command> will not let
you change the return type of an existing function. To do that,
you must drop and recreate the function.
</para>
<para>
......@@ -250,7 +250,14 @@ CREATE [ OR REPLACE ] FUNCTION <replaceable class="parameter">name</replaceable>
<para>
A string defining the function; the meaning depends on the
language. It may be an internal function name, the path to an
object file, an SQL command, or text in a procedural language.
object file, an SQL command, or text in a procedural
language. When this string contains the text of a procedural
language function definition, it may be helpful to use dollar
quoting to specify this string, rather than the normal single
quote syntax (this avoids the need to escape any single quotes
that occur in the function definition itself). For more
information on dollar quoting, see <xref
linkend="sql-syntax-strings">.
</para>
</listitem>
</varlistentry>
......@@ -350,13 +357,14 @@ CREATE [ OR REPLACE ] FUNCTION <replaceable class="parameter">name</replaceable>
</para>
<para>
Use <command>DROP FUNCTION</command>
to remove user-defined functions.
Use <xref linkend="sql-dropfunction"
endterm="sql-dropfunction-title"> to remove user-defined
functions.
</para>
<para>
Any single quotes or backslashes in the function definition must be
escaped by doubling them.
Unless dollar quoting is used, any single quotes or backslashes in
the function definition must be escaped by doubling them.
</para>
<para>
......@@ -374,7 +382,7 @@ CREATE [ OR REPLACE ] FUNCTION <replaceable class="parameter">name</replaceable>
information and examples, see <xref linkend="xfunc">.
<programlisting>
CREATE FUNCTION add(integer, integer) RETURNS integer
AS 'select $1 + $2;'
AS $$select $1 + $2;$$
LANGUAGE SQL
IMMUTABLE
RETURNS NULL ON NULL INPUT;
......
doc/src/sgml/ref/create_type.sgml
浏览文件 @ 8295c27c
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/create_type.sgml,v 1.49 2004/02/12 23:41:02 tgl Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/create_type.sgml,v 1.50 2004/05/16 23:22:07 neilc Exp $
PostgreSQL documentation
-->
......@@ -466,8 +466,9 @@ CREATE TYPE <replaceable class="parameter">name</replaceable> (
a function definition:
<programlisting>
CREATE TYPE compfoo AS (f1 int, f2 text);
CREATE FUNCTION getfoo() RETURNS SETOF compfoo AS
'SELECT fooid, fooname FROM foo' LANGUAGE SQL;
CREATE FUNCTION getfoo() RETURNS SETOF compfoo AS $$
SELECT fooid, fooname FROM foo
$$ LANGUAGE SQL;
</programlisting>
</para>
......
doc/src/sgml/ref/select.sgml
浏览文件 @ 8295c27c
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/select.sgml,v 1.76 2004/03/09 16:57:47 neilc Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/select.sgml,v 1.77 2004/05/16 23:22:08 neilc Exp $
PostgreSQL documentation
-->
......@@ -938,18 +938,18 @@ SELECT actors.name
clause, both with and without a column definition list:
<programlisting>
CREATE FUNCTION distributors(int) RETURNS SETOF distributors AS '
CREATE FUNCTION distributors(int) RETURNS SETOF distributors AS $$
SELECT * FROM distributors WHERE did = $1;
' LANGUAGE SQL;
$$ LANGUAGE SQL;
SELECT * FROM distributors(111);
did | name
-----+-------------
111 | Walt Disney
CREATE FUNCTION distributors_2(int) RETURNS SETOF record AS '
CREATE FUNCTION distributors_2(int) RETURNS SETOF record AS $$
SELECT * FROM distributors WHERE did = $1;
' LANGUAGE SQL;
$$ LANGUAGE SQL;
SELECT * FROM distributors_2(111) AS (f1 int, f2 text);
f1 | f2
......
doc/src/sgml/rules.sgml
浏览文件 @ 8295c27c
<!-- $PostgreSQL: pgsql/doc/src/sgml/rules.sgml,v 1.34 2004/03/09 05:05:40 momjian Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/rules.sgml,v 1.35 2004/05/16 23:22:07 neilc Exp $ -->
<Chapter Id="rules">
<Title>The Rule System</Title>
......@@ -343,9 +343,9 @@ For the example, we need a little <literal>min</literal> function that
returns the lower of 2 integer values. We create that as
<ProgramListing>
CREATE FUNCTION min(integer, integer) RETURNS integer AS '
CREATE FUNCTION min(integer, integer) RETURNS integer AS $$
SELECT CASE WHEN $1 < $2 THEN $1 ELSE $2 END
' LANGUAGE SQL STRICT;
$$ LANGUAGE SQL STRICT;
</ProgramListing>
</Para>
......
doc/src/sgml/syntax.sgml
浏览文件 @ 8295c27c
<!--
$PostgreSQL: pgsql/doc/src/sgml/syntax.sgml,v 1.91 2004/05/10 22:44:43 tgl Exp $
$PostgreSQL: pgsql/doc/src/sgml/syntax.sgml,v 1.92 2004/05/16 23:22:07 neilc Exp $
-->
<chapter id="sql-syntax">
......@@ -240,15 +240,73 @@ UPDATE "my_table" SET "a" = 5;
<primary>quotation marks</primary>
<secondary>escaping</secondary>
</indexterm>
A string constant in SQL is an arbitrary sequence of characters
bounded by single quotes (<literal>'</literal>), e.g., <literal>'This
is a string'</literal>. SQL allows single quotes to be embedded
in strings by typing two adjacent single quotes, e.g.,
<literal>'Dianne''s horse'</literal>. In
<productname>PostgreSQL</productname> single quotes may
alternatively be escaped with a backslash (<literal>\</literal>),
e.g., <literal>'Dianne\'s horse'</literal>.
</para>
<indexterm>
<primary>dollar quoting</primary>
</indexterm>
<productname>PostgreSQL</productname> provides two ways to
specify a string constant. The first way is to enclose the
sequence of characters that constitute the string in single
quotes (<literal>'</literal>), e.g. <literal>'This is a
string'</literal>. This method of specifying a string constant
is defined by the SQL standard. The standard-compliant way of
embedding single-quotes these kinds of string constants is by
typing two adjacent single quotes, e.g. <literal>'Dianne''s
house'</literal>. In addition,
<productname>PostgreSQL</productname> allows single quotes
to be escaped with a backslash (<literal>\</literal>),
e.g. <literal>'Dianne\'s horse'</literal>.
</para>
<para>
While this syntax for specifying string constants is usually
convenient, it can be difficult to comprehend the content of the
string if it consists of many single quotes, each of which must
be doubled. To allows more readable queries in these situations,
<productname>PostgreSQL</productname> allows another way to
specify string constants known as <quote>dollar
quoting</quote>. A string constant specified via dollar quoting
consists of a dollar sign (<literal>$</literal>), an optional
<quote>tag</quote> of zero or more characters, another dollar
sign, an arbitrary sequence of characters that makes up the
string content, a dollar sign, the same tag that began this
dollar quote, and a dollar sign. For example, here are two
different ways to specify the previous example using dollar
quoting:
<programlisting>
$$Dianne's horse$$
$SomeTag$Dianne's horse$SomeTag$
</programlisting>
Note that inside the dollar-quoted string, single quotes can be
used without needing to be escaped.
</para>
<para>
Dollar quotes are case sensitive, so <literal>$tag$String
content$tag$</literal> is valid, but <literal>$TAG$String
content$tag$</literal> is not. Also, dollar quotes can
nest. For example:
<programlisting>
CREATE OR REPLACE FUNCTION has_bad_chars(text) RETURNS boolean AS
$function$
BEGIN
RETURN ($1 ~ $q$[\t\r\n\v|\\]$q$);
END;
$function$ LANGUAGE plpgsql;
</programlisting>
Note that nesting requires a different tag for each nested
dollar quote, as shown above. Furthermore, nested dollar quotes
can only be used when the content of the string that is being
quoted will be re-parsed by <productname>PostgreSQL</>.
</para>
<para>
Dollar quoting is not defined by the SQL standard, but it is
often a more convenient way to write long string literals (such
as procedural function definitions) than the standard-compliant
single quote syntax. Which quoting technique is most appropriate
for a particular circumstance is a decision that is left to the
user.
</para>
<para>
C-style backslash escapes are also available:
......@@ -1008,7 +1066,7 @@ $<replaceable>number</replaceable>
<programlisting>
CREATE FUNCTION dept(text) RETURNS dept
AS 'SELECT * FROM dept WHERE name = $1'
AS $$SELECT * FROM dept WHERE name = $1$$
LANGUAGE SQL;
</programlisting>
......
doc/src/sgml/xfunc.sgml
浏览文件 @ 8295c27c
<!--
$PostgreSQL: pgsql/doc/src/sgml/xfunc.sgml,v 1.83 2004/05/14 21:42:27 neilc Exp $
$PostgreSQL: pgsql/doc/src/sgml/xfunc.sgml,v 1.84 2004/05/16 23:22:07 neilc Exp $
-->
<sect1 id="xfunc">
......@@ -104,13 +104,13 @@ $PostgreSQL: pgsql/doc/src/sgml/xfunc.sgml,v 1.83 2004/05/14 21:42:27 neilc Exp
<para>
The body of an SQL function should be a list of one or more SQL
statements separated by semicolons. Note that because the syntax
of the <command>CREATE FUNCTION</command> command requires the body of the
function to be enclosed in single quotes, single quote marks
(<literal>'</>) used
in the body of the function must be escaped, by writing two single
quotes (<literal>''</>) or a backslash (<literal>\'</>) where each
quote is desired.
statements separated by semicolons. Although dollar quoting
obviates this, note that because the syntax of the <command>CREATE
FUNCTION</command> command, if you choose not to use dollar
quoting, i.e. the body of the function is enclosed in single quotes,
you must escape single quote marks (<literal>'</>) used in the body of
the function, either by writing two single quotes (<literal>''</>) or
with a backslash (<literal>\'</>) where you desire each quote to be.
</para>
<para>
......@@ -130,6 +130,11 @@ $PostgreSQL: pgsql/doc/src/sgml/xfunc.sgml,v 1.83 2004/05/14 21:42:27 neilc Exp
simply returns a base type, such as <type>integer</type>:
<screen>
CREATE FUNCTION one() RETURNS integer AS $$
SELECT 1 AS result;
$$ LANGUAGE SQL;
-- Alternative syntax:
CREATE FUNCTION one() RETURNS integer AS '
SELECT 1 AS result;
' LANGUAGE SQL;
......@@ -156,9 +161,9 @@ SELECT one();
and <literal>$2</>.
<screen>
CREATE FUNCTION add_em(integer, integer) RETURNS integer AS '
CREATE FUNCTION add_em(integer, integer) RETURNS integer AS $$
SELECT $1 + $2;
' LANGUAGE SQL;
$$ LANGUAGE SQL;
SELECT add_em(1, 2) AS answer;
......@@ -173,12 +178,12 @@ SELECT add_em(1, 2) AS answer;
bank account:
<programlisting>
CREATE FUNCTION tf1 (integer, numeric) RETURNS integer AS '
CREATE FUNCTION tf1 (integer, numeric) RETURNS integer AS $$
UPDATE bank
SET balance = balance - $2
WHERE accountno = $1;
SELECT 1;
' LANGUAGE SQL;
$$ LANGUAGE SQL;
</programlisting>
A user could execute this function to debit account 17 by $100.00 as
......@@ -195,12 +200,12 @@ SELECT tf1(17, 100.0);
is
<programlisting>
CREATE FUNCTION tf1 (integer, numeric) RETURNS numeric AS '
CREATE FUNCTION tf1 (integer, numeric) RETURNS numeric AS $$
UPDATE bank
SET balance = balance - $2
WHERE accountno = $1;
SELECT balance FROM bank WHERE accountno = $1;
' LANGUAGE SQL;
$$ LANGUAGE SQL;
</programlisting>
which adjusts the balance and returns the new balance.
......@@ -221,10 +226,10 @@ CREATE FUNCTION tf1 (integer, numeric) RETURNS numeric AS '
For example:
<screen>
CREATE FUNCTION clean_emp() RETURNS void AS '
CREATE FUNCTION clean_emp() RETURNS void AS $$
DELETE FROM emp
WHERE salary &lt;= 0;
' LANGUAGE SQL;
$$ LANGUAGE SQL;
SELECT clean_emp();
......@@ -258,9 +263,9 @@ CREATE TABLE emp (
cubicle point
);
CREATE FUNCTION double_salary(emp) RETURNS numeric AS '
CREATE FUNCTION double_salary(emp) RETURNS numeric AS $$
SELECT $1.salary * 2 AS salary;
' LANGUAGE SQL;
$$ LANGUAGE SQL;
SELECT name, double_salary(emp.*) AS dream
FROM emp
......@@ -304,12 +309,12 @@ SELECT name, double_salary(row(name, salary*1.1, age, cubicle)) AS dream
that returns a single <type>emp</type> row:
<programlisting>
CREATE FUNCTION new_emp() RETURNS emp AS '
SELECT text ''None'' AS name,
CREATE FUNCTION new_emp() RETURNS emp AS $$
SELECT text 'None' AS name,
1000 AS salary,
25 AS age,
point ''(2,2)'' AS cubicle;
' LANGUAGE SQL;
point '(2,2)' AS cubicle;
$$ LANGUAGE SQL;
</programlisting>
In this example we have specified each of the attributes
......@@ -405,9 +410,9 @@ SELECT name(emp) AS youngster
result of the first function to it:
<screen>
CREATE FUNCTION getname(emp) RETURNS text AS '
CREATE FUNCTION getname(emp) RETURNS text AS $$
SELECT $1.name;
' LANGUAGE SQL;
$$ LANGUAGE SQL;
SELECT getname(new_emp());
getname
......@@ -439,9 +444,9 @@ INSERT INTO foo VALUES (1, 1, 'Joe');
INSERT INTO foo VALUES (1, 2, 'Ed');
INSERT INTO foo VALUES (2, 1, 'Mary');
CREATE FUNCTION getfoo(int) RETURNS foo AS '
CREATE FUNCTION getfoo(int) RETURNS foo AS $$
SELECT * FROM foo WHERE fooid = $1;
' LANGUAGE SQL;
$$ LANGUAGE SQL;
SELECT *, upper(fooname) FROM getfoo(1) AS t1;
......@@ -478,9 +483,9 @@ SELECT *, upper(fooname) FROM getfoo(1) AS t1;
table <literal>foo</> has the same contents as above, and we say:
<programlisting>
CREATE FUNCTION getfoo(int) RETURNS SETOF foo AS '
CREATE FUNCTION getfoo(int) RETURNS SETOF foo AS $$
SELECT * FROM foo WHERE fooid = $1;
' LANGUAGE SQL;
$$ LANGUAGE SQL;
SELECT * FROM getfoo(1) AS t1;
</programlisting>
......@@ -505,9 +510,9 @@ SELECT * FROM getfoo(1) AS t1;
select list:
<screen>
CREATE FUNCTION listchildren(text) RETURNS SETOF text AS
'SELECT name FROM nodes WHERE parent = $1'
LANGUAGE SQL;
CREATE FUNCTION listchildren(text) RETURNS SETOF text AS $$
SELECT name FROM nodes WHERE parent = $1
$$ LANGUAGE SQL;
SELECT * FROM nodes;
name | parent
......@@ -558,9 +563,9 @@ SELECT name, listchildren(name) FROM nodes;
function <function>make_array</function> that builds up an array
from two arbitrary data type elements:
<screen>
CREATE FUNCTION make_array(anyelement, anyelement) RETURNS anyarray AS '
CREATE FUNCTION make_array(anyelement, anyelement) RETURNS anyarray AS $$
SELECT ARRAY[$1, $2];
' LANGUAGE SQL;
$$ LANGUAGE SQL;
SELECT make_array(1, 2) AS intarray, make_array('a'::text, 'b') AS textarray;
intarray | textarray
......@@ -589,9 +594,9 @@ ERROR: could not determine "anyarray"/"anyelement" type because input has type
It is permitted to have polymorphic arguments with a deterministic
return type, but the converse is not. For example:
<screen>
CREATE FUNCTION is_greater(anyelement, anyelement) RETURNS boolean AS '
CREATE FUNCTION is_greater(anyelement, anyelement) RETURNS boolean AS $$
SELECT $1 > $2;
' LANGUAGE SQL;
$$ LANGUAGE SQL;
SELECT is_greater(1, 2);
is_greater
......@@ -599,9 +604,9 @@ SELECT is_greater(1, 2);
f
(1 row)
CREATE FUNCTION invalid_func() RETURNS anyelement AS '
CREATE FUNCTION invalid_func() RETURNS anyelement AS $$
SELECT 1;
' LANGUAGE SQL;
$$ LANGUAGE SQL;
ERROR: cannot determine result data type
DETAIL: A function returning "anyarray" or "anyelement" must have at least one argument of either type.
</screen>
......@@ -659,7 +664,7 @@ DETAIL: A function returning "anyarray" or "anyelement" must have at least one
create an alias for the <function>sqrt</function> function:
<programlisting>
CREATE FUNCTION square_root(double precision) RETURNS double precision
AS 'dsqrt'
AS $$dsqrt$$
LANGUAGE internal
STRICT;
</programlisting>
......
Markdown is supported
0% 或 .
You are about to add 0 people to the discussion. Proceed with caution.
先完成此消息的编辑！
想要评论请 注册 或