diff options
| author | Andrew Dunstan <andrew@dunslane.net> | 2025-08-04 08:56:48 -0400 |
|---|---|---|
| committer | Andrew Dunstan <andrew@dunslane.net> | 2025-08-04 09:04:56 -0400 |
| commit | 4e23c9ef65accde7eb3e56aa28d50ae5cf79b64b (patch) | |
| tree | e56f52b0d1b8409794a5ac0cc54ee7a322c58c6a /doc/src/sgml/func/func-logical.sgml | |
| parent | 6ae268cf284c5a706455e164f8879bd721296535 (diff) | |
Split func.sgml into more manageable pieces
func.sgml has grown over the years to the point where it is very
difficult to manage. This commit splits out each sect1 piece into its
own file, which is then included in the main file, so that the built
documentation should be identical to the pre-split documentation. All
these new files are placed in a new "func" subdirectory, and the
previous func.sgml is removed.
Done using scripts developed by:
Author: jian he <jian.universality@gmail.com>
Discussion: https://postgr.es/m/CACJufxFgAh1--EMwOjMuANe=VTmjkNaZjH+AzSe04-8ZCGiESA@mail.gmail.com
Diffstat (limited to 'doc/src/sgml/func/func-logical.sgml')
| -rw-r--r-- | doc/src/sgml/func/func-logical.sgml | 146 |
1 files changed, 146 insertions, 0 deletions
diff --git a/doc/src/sgml/func/func-logical.sgml b/doc/src/sgml/func/func-logical.sgml new file mode 100644 index 00000000000..65e50e65a81 --- /dev/null +++ b/doc/src/sgml/func/func-logical.sgml @@ -0,0 +1,146 @@ + <sect1 id="functions-logical"> + <title>Logical Operators</title> + + <indexterm zone="functions-logical"> + <primary>operator</primary> + <secondary>logical</secondary> + </indexterm> + + <indexterm> + <primary>Boolean</primary> + <secondary>operators</secondary> + <see>operators, logical</see> + </indexterm> + + <para> + The usual logical operators are available: + + <indexterm> + <primary>AND (operator)</primary> + </indexterm> + + <indexterm> + <primary>OR (operator)</primary> + </indexterm> + + <indexterm> + <primary>NOT (operator)</primary> + </indexterm> + + <indexterm> + <primary>conjunction</primary> + </indexterm> + + <indexterm> + <primary>disjunction</primary> + </indexterm> + + <indexterm> + <primary>negation</primary> + </indexterm> + +<synopsis> +<type>boolean</type> <literal>AND</literal> <type>boolean</type> <returnvalue>boolean</returnvalue> +<type>boolean</type> <literal>OR</literal> <type>boolean</type> <returnvalue>boolean</returnvalue> +<literal>NOT</literal> <type>boolean</type> <returnvalue>boolean</returnvalue> +</synopsis> + + <acronym>SQL</acronym> uses a three-valued logic system with true, + false, and <literal>null</literal>, which represents <quote>unknown</quote>. + Observe the following truth tables: + + <informaltable> + <tgroup cols="4"> + <thead> + <row> + <entry><replaceable>a</replaceable></entry> + <entry><replaceable>b</replaceable></entry> + <entry><replaceable>a</replaceable> AND <replaceable>b</replaceable></entry> + <entry><replaceable>a</replaceable> OR <replaceable>b</replaceable></entry> + </row> + </thead> + + <tbody> + <row> + <entry>TRUE</entry> + <entry>TRUE</entry> + <entry>TRUE</entry> + <entry>TRUE</entry> + </row> + + <row> + <entry>TRUE</entry> + <entry>FALSE</entry> + <entry>FALSE</entry> + <entry>TRUE</entry> + </row> + + <row> + <entry>TRUE</entry> + <entry>NULL</entry> + <entry>NULL</entry> + <entry>TRUE</entry> + </row> + + <row> + <entry>FALSE</entry> + <entry>FALSE</entry> + <entry>FALSE</entry> + <entry>FALSE</entry> + </row> + + <row> + <entry>FALSE</entry> + <entry>NULL</entry> + <entry>FALSE</entry> + <entry>NULL</entry> + </row> + + <row> + <entry>NULL</entry> + <entry>NULL</entry> + <entry>NULL</entry> + <entry>NULL</entry> + </row> + </tbody> + </tgroup> + </informaltable> + + <informaltable> + <tgroup cols="2"> + <thead> + <row> + <entry><replaceable>a</replaceable></entry> + <entry>NOT <replaceable>a</replaceable></entry> + </row> + </thead> + + <tbody> + <row> + <entry>TRUE</entry> + <entry>FALSE</entry> + </row> + + <row> + <entry>FALSE</entry> + <entry>TRUE</entry> + </row> + + <row> + <entry>NULL</entry> + <entry>NULL</entry> + </row> + </tbody> + </tgroup> + </informaltable> + </para> + + <para> + The operators <literal>AND</literal> and <literal>OR</literal> are + commutative, that is, you can switch the left and right operands + without affecting the result. (However, it is not guaranteed that + the left operand is evaluated before the right operand. See <xref + linkend="syntax-express-eval"/> for more information about the + order of evaluation of subexpressions.) + </para> + </sect1> |