Author: paul
Date: 2006-01-20 05:33:02 +0100 (Fri, 20 Jan 2006)
New Revision: 943
Log:
r6471@frost: paul | 2006-01-19 21:20:42 -0600
Set up explicit type-conversion section.
Modified:
trunk/
trunk/refman-4.1/functions.xml
trunk/refman-5.0/functions.xml
trunk/refman-5.1/functions.xml
Property changes on: trunk
___________________________________________________________________
Name: svk:merge
- b5ec3a16-e900-0410-9ad2-d183a3acac99:/mysqldoc-local/mysqldoc/trunk:6470
bf112a9c-6c03-0410-a055-ad865cd57414:/mysqldoc-local/mysqldoc/trunk:2335
+ b5ec3a16-e900-0410-9ad2-d183a3acac99:/mysqldoc-local/mysqldoc/trunk:6471
bf112a9c-6c03-0410-a055-ad865cd57414:/mysqldoc-local/mysqldoc/trunk:2335
Modified: trunk/refman-4.1/functions.xml
===================================================================
--- trunk/refman-4.1/functions.xml 2006-01-20 04:32:46 UTC (rev 942)
+++ trunk/refman-4.1/functions.xml 2006-01-20 04:33:02 UTC (rev 943)
@@ -169,45 +169,50 @@
</section>
- <section id="comparison-operators">
+ <section id="type-conversion">
- <title>&title-comparison-operators;</title>
+ <title>&title-type-conversion;</title>
- <indexterm type="function">
- <primary>comparison operators</primary>
+ <indexterm>
+ <primary>type conversions</primary>
</indexterm>
- <remark role="help-category" condition="Comparison operators@Functions"/>
-
<indexterm>
<primary>casts</primary>
</indexterm>
- <indexterm>
- <primary>type conversions</primary>
- </indexterm>
-
<para>
- Comparison operations result in a value of <literal>1</literal>
- (<literal>TRUE</literal>), <literal>0</literal>
- (<literal>FALSE</literal>), or <literal>NULL</literal>. These
- operations work for both numbers and strings. Strings are
- automatically converted to numbers and numbers to strings as
- necessary.
+ When an operator is used with operands of different types, type
+ conversion occurs to make the operands compatible. Some
+ conversions occur implicitly. For example, MySQL automatically
+ converts numbers to strings as necessary, and vice versa.
</para>
+<programlisting>
+mysql> <userinput>SELECT 1+'1';</userinput>
+ -> 2
+mysql> <userinput>SELECT CONCAT(2,' test');</userinput>
+ -> '2 test'
+</programlisting>
+
<para>
- Some of the functions in this section (such as
- <literal>LEAST()</literal> and <literal>GREATEST()</literal>)
- return values other than <literal>1</literal>
- (<literal>TRUE</literal>), <literal>0</literal>
- (<literal>FALSE</literal>), or <literal>NULL</literal>. However,
- the value they return is based on comparison operations
- performed as described by the following rules.
+ It is also possible to perform explicit conversions. If you want
+ to convert a number to a string explicitly, use the
+ <literal>CAST()</literal> or <literal>CONCAT()</literal>
+ function (<literal>CAST()</literal> is preferable, but is
+ unavailable before MySQL 4.0.2):
</para>
+<programlisting>
+mysql> <userinput>SELECT 38.8, CAST(38.8 AS CHAR);</userinput>
+ -> 38.8, '38.8'
+mysql> <userinput>SELECT 38.8, CONCAT(38.8);</userinput>
+ -> 38.8, '38.8'
+</programlisting>
+
<para>
- MySQL compares values using the following rules:
+ The following rules describe how conversion occurs for
+ comparison operations:
</para>
<itemizedlist>
@@ -218,6 +223,8 @@
result of the comparison is <literal>NULL</literal>, except
for the <literal>NULL</literal>-safe
<literal><=></literal> equality comparison operator.
+ For <literal>NULL <=> NULL</literal>, the result is
+ true.
</para>
</listitem>
@@ -257,8 +264,8 @@
<literal>DATETIME</literal> column and the other argument is
a constant, the constant is converted to a timestamp before
the comparison is performed. This is done to be more
- ODBC-friendly. Note that this is not done for arguments in
- <literal>IN()</literal>! To be safe, always use complete
+ ODBC-friendly. Note that this is not done for the arguments
+ to <literal>IN()</literal>! To be safe, always use complete
datetime/date/time strings when doing comparisons.
</para>
</listitem>
@@ -273,21 +280,6 @@
</itemizedlist>
<para>
- By default, string comparisons are not case sensitive and use
- the current character set. The default is
- <literal>latin1</literal> (cp1252 West European), which also
- works well for English).
- </para>
-
- <para>
- To convert a value to a specific type for comparison purposes,
- you can use the <literal>CAST()</literal> function. String
- values can be converted to a different character set using
- <literal>CONVERT()</literal>. See
- <xref linkend="cast-functions"/>.
- </para>
-
- <para>
The following examples illustrate conversion of strings to
numbers for comparison operations:
</para>
@@ -322,6 +314,61 @@
<literal>'1a'</literal>, ...
</para>
+ </section>
+
+ <section id="comparison-operators">
+
+ <title>&title-comparison-operators;</title>
+
+ <indexterm type="function">
+ <primary>comparison operators</primary>
+ </indexterm>
+
+ <remark role="help-category" condition="Comparison operators@Functions"/>
+
+ <indexterm>
+ <primary>casts</primary>
+ </indexterm>
+
+ <indexterm>
+ <primary>type conversions</primary>
+ </indexterm>
+
+ <para>
+ Comparison operations result in a value of <literal>1</literal>
+ (<literal>TRUE</literal>), <literal>0</literal>
+ (<literal>FALSE</literal>), or <literal>NULL</literal>. These
+ operations work for both numbers and strings. Strings are
+ automatically converted to numbers and numbers to strings as
+ necessary.
+ </para>
+
+ <para>
+ Some of the functions in this section (such as
+ <literal>LEAST()</literal> and <literal>GREATEST()</literal>)
+ return values other than <literal>1</literal>
+ (<literal>TRUE</literal>), <literal>0</literal>
+ (<literal>FALSE</literal>), or <literal>NULL</literal>. However,
+ the value they return is based on comparison operations
+ performed as described by the rules in
+ <xref linkend="type-conversion"/>.
+ </para>
+
+ <para>
+ To convert a value to a specific type for comparison purposes,
+ you can use the <literal>CAST()</literal> function. String
+ values can be converted to a different character set using
+ <literal>CONVERT()</literal>. See
+ <xref linkend="cast-functions"/>.
+ </para>
+
+ <para>
+ By default, string comparisons are not case sensitive and use
+ the current character set. The default is
+ <literal>latin1</literal> (cp1252 West European), which also
+ works well for English.
+ </para>
+
<itemizedlist>
<listitem>
@@ -3887,36 +3934,6 @@
<remark role="help-category" condition="String Functions@Functions"/>
<para>
- MySQL automatically converts numbers to strings as necessary,
- and vice versa.
- </para>
-
-<programlisting>
-mysql> <userinput>SELECT 1+'1';</userinput>
- -> 2
-mysql> <userinput>SELECT CONCAT(2,' test');</userinput>
- -> '2 test'
-</programlisting>
-
- <para>
- If you want to convert a number to a string explicitly, use the
- <literal>CAST()</literal> or <literal>CONCAT()</literal>
- function:
- </para>
-
-<programlisting>
-mysql> <userinput>SELECT 38.8, CAST(38.8 AS CHAR);</userinput>
- -> 38.8, '38.8'
-mysql> <userinput>SELECT 38.8, CONCAT(38.8);</userinput>
- -> 38.8, '38.8'
-</programlisting>
-
- <para>
- <literal>CAST()</literal> is preferable, but it is unavailable
- before MySQL 4.0.2.
- </para>
-
- <para>
If a string function is given a binary string as an argument,
the resulting string is also a binary string. A number converted
to a string is treated as a binary string. This affects only
Modified: trunk/refman-5.0/functions.xml
===================================================================
--- trunk/refman-5.0/functions.xml 2006-01-20 04:32:46 UTC (rev 942)
+++ trunk/refman-5.0/functions.xml 2006-01-20 04:33:02 UTC (rev 943)
@@ -189,45 +189,49 @@
</section>
- <section id="comparison-operators">
+ <section id="type-conversion">
- <title>&title-comparison-operators;</title>
+ <title>&title-type-conversion;</title>
- <indexterm type="function">
- <primary>comparison operators</primary>
+ <indexterm>
+ <primary>type conversions</primary>
</indexterm>
- <remark role="help-category" condition="Comparison operators@Functions"/>
-
<indexterm>
<primary>casts</primary>
</indexterm>
- <indexterm>
- <primary>type conversions</primary>
- </indexterm>
-
<para>
- Comparison operations result in a value of <literal>1</literal>
- (<literal>TRUE</literal>), <literal>0</literal>
- (<literal>FALSE</literal>), or <literal>NULL</literal>. These
- operations work for both numbers and strings. Strings are
- automatically converted to numbers and numbers to strings as
- necessary.
+ When an operator is used with operands of different types, type
+ conversion occurs to make the operands compatible. Some
+ conversions occur implicitly. For example, MySQL automatically
+ converts numbers to strings as necessary, and vice versa.
</para>
+<programlisting>
+mysql> <userinput>SELECT 1+'1';</userinput>
+ -> 2
+mysql> <userinput>SELECT CONCAT(2,' test');</userinput>
+ -> '2 test'
+</programlisting>
+
<para>
- Some of the functions in this section (such as
- <literal>LEAST()</literal> and <literal>GREATEST()</literal>)
- return values other than <literal>1</literal>
- (<literal>TRUE</literal>), <literal>0</literal>
- (<literal>FALSE</literal>), or <literal>NULL</literal>. However,
- the value they return is based on comparison operations
- performed as described by the following rules.
+ It is also possible to perform explicit conversions. If you want
+ to convert a number to a string explicitly, use the
+ <literal>CAST()</literal> or <literal>CONCAT()</literal>
+ function (<literal>CAST()</literal> is preferable):
</para>
+<programlisting>
+mysql> <userinput>SELECT 38.8, CAST(38.8 AS CHAR);</userinput>
+ -> 38.8, '38.8'
+mysql> <userinput>SELECT 38.8, CONCAT(38.8);</userinput>
+ -> 38.8, '38.8'
+</programlisting>
+
<para>
- MySQL compares values using the following rules:
+ The following rules describe how conversion occurs for
+ comparison operations:
</para>
<itemizedlist>
@@ -238,6 +242,8 @@
result of the comparison is <literal>NULL</literal>, except
for the <literal>NULL</literal>-safe
<literal><=></literal> equality comparison operator.
+ For <literal>NULL <=> NULL</literal>, the result is
+ true.
</para>
</listitem>
@@ -277,8 +283,8 @@
<literal>DATETIME</literal> column and the other argument is
a constant, the constant is converted to a timestamp before
the comparison is performed. This is done to be more
- ODBC-friendly. Note that this is not done for arguments in
- <literal>IN()</literal>! To be safe, always use complete
+ ODBC-friendly. Note that this is not done for the arguments
+ to <literal>IN()</literal>! To be safe, always use complete
datetime/date/time strings when doing comparisons.
</para>
</listitem>
@@ -293,21 +299,6 @@
</itemizedlist>
<para>
- By default, string comparisons are not case sensitive and use
- the current character set. The default is
- <literal>latin1</literal> (cp1252 West European), which also
- works well for English).
- </para>
-
- <para>
- To convert a value to a specific type for comparison purposes,
- you can use the <literal>CAST()</literal> function. String
- values can be converted to a different character set using
- <literal>CONVERT()</literal>. See
- <xref linkend="cast-functions"/>.
- </para>
-
- <para>
The following examples illustrate conversion of strings to
numbers for comparison operations:
</para>
@@ -342,6 +333,61 @@
<literal>'1a'</literal>, ...
</para>
+ </section>
+
+ <section id="comparison-operators">
+
+ <title>&title-comparison-operators;</title>
+
+ <indexterm type="function">
+ <primary>comparison operators</primary>
+ </indexterm>
+
+ <remark role="help-category" condition="Comparison operators@Functions"/>
+
+ <indexterm>
+ <primary>casts</primary>
+ </indexterm>
+
+ <indexterm>
+ <primary>type conversions</primary>
+ </indexterm>
+
+ <para>
+ Comparison operations result in a value of <literal>1</literal>
+ (<literal>TRUE</literal>), <literal>0</literal>
+ (<literal>FALSE</literal>), or <literal>NULL</literal>. These
+ operations work for both numbers and strings. Strings are
+ automatically converted to numbers and numbers to strings as
+ necessary.
+ </para>
+
+ <para>
+ Some of the functions in this section (such as
+ <literal>LEAST()</literal> and <literal>GREATEST()</literal>)
+ return values other than <literal>1</literal>
+ (<literal>TRUE</literal>), <literal>0</literal>
+ (<literal>FALSE</literal>), or <literal>NULL</literal>. However,
+ the value they return is based on comparison operations
+ performed as described by the rules in
+ <xref linkend="type-conversion"/>.
+ </para>
+
+ <para>
+ To convert a value to a specific type for comparison purposes,
+ you can use the <literal>CAST()</literal> function. String
+ values can be converted to a different character set using
+ <literal>CONVERT()</literal>. See
+ <xref linkend="cast-functions"/>.
+ </para>
+
+ <para>
+ By default, string comparisons are not case sensitive and use
+ the current character set. The default is
+ <literal>latin1</literal> (cp1252 West European), which also
+ works well for English.
+ </para>
+
<itemizedlist>
<listitem>
@@ -3953,35 +3999,6 @@
<remark role="help-category" condition="String Functions@Functions"/>
<para>
- MySQL automatically converts numbers to strings as necessary,
- and vice versa.
- </para>
-
-<programlisting>
-mysql> <userinput>SELECT 1+'1';</userinput>
- -> 2
-mysql> <userinput>SELECT CONCAT(2,' test');</userinput>
- -> '2 test'
-</programlisting>
-
- <para>
- If you want to convert a number to a string explicitly, use the
- <literal>CAST()</literal> or <literal>CONCAT()</literal>
- function:
- </para>
-
-<programlisting>
-mysql> <userinput>SELECT 38.8, CAST(38.8 AS CHAR);</userinput>
- -> 38.8, '38.8'
-mysql> <userinput>SELECT 38.8, CONCAT(38.8);</userinput>
- -> 38.8, '38.8'
-</programlisting>
-
- <para>
- <literal>CAST()</literal> is preferable.
- </para>
-
- <para>
If a string function is given a binary string as an argument,
the resulting string is also a binary string. A number converted
to a string is treated as a binary string. This affects only
Modified: trunk/refman-5.1/functions.xml
===================================================================
--- trunk/refman-5.1/functions.xml 2006-01-20 04:32:46 UTC (rev 942)
+++ trunk/refman-5.1/functions.xml 2006-01-20 04:33:02 UTC (rev 943)
@@ -188,45 +188,49 @@
</section>
- <section id="comparison-operators">
+ <section id="type-conversion">
- <title>&title-comparison-operators;</title>
+ <title>&title-type-conversion;</title>
- <indexterm type="function">
- <primary>comparison operators</primary>
+ <indexterm>
+ <primary>type conversions</primary>
</indexterm>
- <remark role="help-category" condition="Comparison operators@Functions"/>
-
<indexterm>
<primary>casts</primary>
</indexterm>
- <indexterm>
- <primary>type conversions</primary>
- </indexterm>
-
<para>
- Comparison operations result in a value of <literal>1</literal>
- (<literal>TRUE</literal>), <literal>0</literal>
- (<literal>FALSE</literal>), or <literal>NULL</literal>. These
- operations work for both numbers and strings. Strings are
- automatically converted to numbers and numbers to strings as
- necessary.
+ When an operator is used with operands of different types, type
+ conversion occurs to make the operands compatible. Some
+ conversions occur implicitly. For example, MySQL automatically
+ converts numbers to strings as necessary, and vice versa.
</para>
+<programlisting>
+mysql> <userinput>SELECT 1+'1';</userinput>
+ -> 2
+mysql> <userinput>SELECT CONCAT(2,' test');</userinput>
+ -> '2 test'
+</programlisting>
+
<para>
- Some of the functions in this section (such as
- <literal>LEAST()</literal> and <literal>GREATEST()</literal>)
- return values other than <literal>1</literal>
- (<literal>TRUE</literal>), <literal>0</literal>
- (<literal>FALSE</literal>), or <literal>NULL</literal>. However,
- the value they return is based on comparison operations
- performed as described by the following rules.
+ It is also possible to perform explicit conversions. If you want
+ to convert a number to a string explicitly, use the
+ <literal>CAST()</literal> or <literal>CONCAT()</literal>
+ function (<literal>CAST()</literal> is preferable):
</para>
+<programlisting>
+mysql> <userinput>SELECT 38.8, CAST(38.8 AS CHAR);</userinput>
+ -> 38.8, '38.8'
+mysql> <userinput>SELECT 38.8, CONCAT(38.8);</userinput>
+ -> 38.8, '38.8'
+</programlisting>
+
<para>
- MySQL compares values using the following rules:
+ The following rules describe how conversion occurs for
+ comparison operations:
</para>
<itemizedlist>
@@ -237,6 +241,8 @@
result of the comparison is <literal>NULL</literal>, except
for the <literal>NULL</literal>-safe
<literal><=></literal> equality comparison operator.
+ For <literal>NULL <=> NULL</literal>, the result is
+ true.
</para>
</listitem>
@@ -276,8 +282,8 @@
<literal>DATETIME</literal> column and the other argument is
a constant, the constant is converted to a timestamp before
the comparison is performed. This is done to be more
- ODBC-friendly. Note that this is not done for arguments in
- <literal>IN()</literal>! To be safe, always use complete
+ ODBC-friendly. Note that this is not done for the arguments
+ to <literal>IN()</literal>! To be safe, always use complete
datetime/date/time strings when doing comparisons.
</para>
</listitem>
@@ -292,21 +298,6 @@
</itemizedlist>
<para>
- By default, string comparisons are not case sensitive and use
- the current character set. The default is
- <literal>latin1</literal> (cp1252 West European), which also
- works well for English).
- </para>
-
- <para>
- To convert a value to a specific type for comparison purposes,
- you can use the <literal>CAST()</literal> function. String
- values can be converted to a different character set using
- <literal>CONVERT()</literal>. See
- <xref linkend="cast-functions"/>.
- </para>
-
- <para>
The following examples illustrate conversion of strings to
numbers for comparison operations:
</para>
@@ -341,6 +332,61 @@
<literal>'1a'</literal>, ...
</para>
+ </section>
+
+ <section id="comparison-operators">
+
+ <title>&title-comparison-operators;</title>
+
+ <indexterm type="function">
+ <primary>comparison operators</primary>
+ </indexterm>
+
+ <remark role="help-category" condition="Comparison operators@Functions"/>
+
+ <indexterm>
+ <primary>casts</primary>
+ </indexterm>
+
+ <indexterm>
+ <primary>type conversions</primary>
+ </indexterm>
+
+ <para>
+ Comparison operations result in a value of <literal>1</literal>
+ (<literal>TRUE</literal>), <literal>0</literal>
+ (<literal>FALSE</literal>), or <literal>NULL</literal>. These
+ operations work for both numbers and strings. Strings are
+ automatically converted to numbers and numbers to strings as
+ necessary.
+ </para>
+
+ <para>
+ Some of the functions in this section (such as
+ <literal>LEAST()</literal> and <literal>GREATEST()</literal>)
+ return values other than <literal>1</literal>
+ (<literal>TRUE</literal>), <literal>0</literal>
+ (<literal>FALSE</literal>), or <literal>NULL</literal>. However,
+ the value they return is based on comparison operations
+ performed as described by the rules in
+ <xref linkend="type-conversion"/>.
+ </para>
+
+ <para>
+ To convert a value to a specific type for comparison purposes,
+ you can use the <literal>CAST()</literal> function. String
+ values can be converted to a different character set using
+ <literal>CONVERT()</literal>. See
+ <xref linkend="cast-functions"/>.
+ </para>
+
+ <para>
+ By default, string comparisons are not case sensitive and use
+ the current character set. The default is
+ <literal>latin1</literal> (cp1252 West European), which also
+ works well for English.
+ </para>
+
<itemizedlist>
<listitem>
@@ -3925,35 +3971,6 @@
<remark role="help-category" condition="String Functions@Functions"/>
<para>
- MySQL automatically converts numbers to strings as necessary,
- and vice versa.
- </para>
-
-<programlisting>
-mysql> <userinput>SELECT 1+'1';</userinput>
- -> 2
-mysql> <userinput>SELECT CONCAT(2,' test');</userinput>
- -> '2 test'
-</programlisting>
-
- <para>
- If you want to convert a number to a string explicitly, use the
- <literal>CAST()</literal> or <literal>CONCAT()</literal>
- function:
- </para>
-
-<programlisting>
-mysql> <userinput>SELECT 38.8, CAST(38.8 AS CHAR);</userinput>
- -> 38.8, '38.8'
-mysql> <userinput>SELECT 38.8, CONCAT(38.8);</userinput>
- -> 38.8, '38.8'
-</programlisting>
-
- <para>
- <literal>CAST()</literal> is preferable.
- </para>
-
- <para>
If a string function is given a binary string as an argument,
the resulting string is also a binary string. A number converted
to a string is treated as a binary string. This affects only
| Thread |
|---|
| • svn commit - mysqldoc@docsrva: r943 - in trunk: . refman-4.1 refman-5.0 refman-5.1 | paul | 20 Jan |
