diff options
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/func.sgml | 43 |
1 files changed, 38 insertions, 5 deletions
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml index 8ecc02f2b90..93b0bc2bc6e 100644 --- a/doc/src/sgml/func.sgml +++ b/doc/src/sgml/func.sgml @@ -1865,6 +1865,39 @@ SELECT NOT(ROW(table.*) IS NOT NULL) FROM TABLE; -- detect at least one null in <row> <entry role="func_table_entry"><para role="func_signature"> <indexterm> + <primary>random</primary> + </indexterm> + <function>random</function> ( <parameter>min</parameter> <type>integer</type>, <parameter>max</parameter> <type>integer</type> ) + <returnvalue>integer</returnvalue> + </para> + <para role="func_signature"> + <function>random</function> ( <parameter>min</parameter> <type>bigint</type>, <parameter>max</parameter> <type>bigint</type> ) + <returnvalue>bigint</returnvalue> + </para> + <para role="func_signature"> + <function>random</function> ( <parameter>min</parameter> <type>numeric</type>, <parameter>max</parameter> <type>numeric</type> ) + <returnvalue>numeric</returnvalue> + </para> + <para> + Returns a random value in the range + <parameter>min</parameter> <= x <= <parameter>max</parameter>. + For type <type>numeric</type>, the result will have the same number of + fractional decimal digits as <parameter>min</parameter> or + <parameter>max</parameter>, whichever has more. + </para> + <para> + <literal>random(1, 10)</literal> + <returnvalue>7</returnvalue> + </para> + <para> + <literal>random(-0.499, 0.499)</literal> + <returnvalue>0.347</returnvalue> + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <indexterm> <primary>random_normal</primary> </indexterm> @@ -1906,19 +1939,19 @@ SELECT NOT(ROW(table.*) IS NOT NULL) FROM TABLE; -- detect at least one null in </table> <para> - The <function>random()</function> function uses a deterministic - pseudo-random number generator. + The <function>random()</function> and <function>random_normal()</function> + functions listed in <xref linkend="functions-math-random-table"/> use a + deterministic pseudo-random number generator. It is fast but not suitable for cryptographic applications; see the <xref linkend="pgcrypto"/> module for a more secure alternative. If <function>setseed()</function> is called, the series of results of - subsequent <function>random()</function> calls in the current session + subsequent calls to these functions in the current session can be repeated by re-issuing <function>setseed()</function> with the same argument. Without any prior <function>setseed()</function> call in the same - session, the first <function>random()</function> call obtains a seed + session, the first call to any of these functions obtains a seed from a platform-dependent source of random bits. - These remarks hold equally for <function>random_normal()</function>. </para> <para> |