relations.sgml

GLib是GTK+和GNOME工程的基础底层核心程序库

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<title><anchor id="g-relation-count">g_relation_count ()</title>
<programlisting><link linkend="gint">gint</link>        g_relation_count                (<link linkend="GRelation">GRelation</link> *relation,
                                             <link linkend="gconstpointer">gconstpointer</link> key,
                                             <link linkend="gint">gint</link> field);</programlisting>
<para>
Returns the number of tuples in a <link linkend="GRelation">GRelation</link> that have the given value
in the given field.
</para><informaltable pgwide="1" frame="none" role="params">
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<colspec colwidth="2*">
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<tbody>
<row><entry align="right"><parameter>relation</parameter>&nbsp;:</entry>
<entry>a <link linkend="GRelation">GRelation</link>.
</entry></row>
<row><entry align="right"><parameter>key</parameter>&nbsp;:</entry>
<entry>the value to compare with.
</entry></row>
<row><entry align="right"><parameter>field</parameter>&nbsp;:</entry>
<entry>the field of each record to match.
</entry></row>
<row><entry align="right"><emphasis>Returns</emphasis> :</entry><entry>the number of matches.


</entry></row>
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<refsect2>
<title><anchor id="g-relation-select">g_relation_select ()</title>
<programlisting><link linkend="GTuples">GTuples</link>*    g_relation_select               (<link linkend="GRelation">GRelation</link> *relation,
                                             <link linkend="gconstpointer">gconstpointer</link> key,
                                             <link linkend="gint">gint</link> field);</programlisting>
<para>
Returns all of the tuples which have the given key in the given field.
Use <link linkend="g-tuples-index">g_tuples_index</link>() to access the returned records.
The returned records should be freed with <link linkend="g-tuples-destroy">g_tuples_destroy</link>().
</para><informaltable pgwide="1" frame="none" role="params">
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<colspec colwidth="2*">
<colspec colwidth="8*">
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<row><entry align="right"><parameter>relation</parameter>&nbsp;:</entry>
<entry>a <link linkend="GRelation">GRelation</link>.
</entry></row>
<row><entry align="right"><parameter>key</parameter>&nbsp;:</entry>
<entry>the value to compare with.
</entry></row>
<row><entry align="right"><parameter>field</parameter>&nbsp;:</entry>
<entry>the field of each record to match.
</entry></row>
<row><entry align="right"><emphasis>Returns</emphasis> :</entry><entry>the records (tuples) that matched.


</entry></row>
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<title><anchor id="g-relation-delete">g_relation_delete ()</title>
<programlisting><link linkend="gint">gint</link>        g_relation_delete               (<link linkend="GRelation">GRelation</link> *relation,
                                             <link linkend="gconstpointer">gconstpointer</link> key,
                                             <link linkend="gint">gint</link> field);</programlisting>
<para>
Deletes any records from a <link linkend="GRelation">GRelation</link> that have the given key value in
the given field.
</para><informaltable pgwide="1" frame="none" role="params">
<tgroup cols="2">
<colspec colwidth="2*">
<colspec colwidth="8*">
<tbody>
<row><entry align="right"><parameter>relation</parameter>&nbsp;:</entry>
<entry>a <link linkend="GRelation">GRelation</link>.
</entry></row>
<row><entry align="right"><parameter>key</parameter>&nbsp;:</entry>
<entry>the value to compare with.
</entry></row>
<row><entry align="right"><parameter>field</parameter>&nbsp;:</entry>
<entry>the field of each record to match.
</entry></row>
<row><entry align="right"><emphasis>Returns</emphasis> :</entry><entry>the number of records deleted.


</entry></row>
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<title><anchor id="g-relation-destroy">g_relation_destroy ()</title>
<programlisting>void        g_relation_destroy              (<link linkend="GRelation">GRelation</link> *relation);</programlisting>
<para>
Destroys the <link linkend="GRelation">GRelation</link>, freeing all memory allocated.
However, it does not free memory allocated for the
tuple data, so you should free that first if appropriate.
</para><informaltable pgwide="1" frame="none" role="params">
<tgroup cols="2">
<colspec colwidth="2*">
<colspec colwidth="8*">
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<row><entry align="right"><parameter>relation</parameter>&nbsp;:</entry>
<entry>a <link linkend="GRelation">GRelation</link>.


</entry></row>
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<title><anchor id="g-relation-print">g_relation_print ()</title>
<programlisting>void        g_relation_print                (<link linkend="GRelation">GRelation</link> *relation);</programlisting>
<para>
Outputs information about all records in a <link linkend="GRelation">GRelation</link>, as well as the indexes.
It is for debugging.
</para><informaltable pgwide="1" frame="none" role="params">
<tgroup cols="2">
<colspec colwidth="2*">
<colspec colwidth="8*">
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<row><entry align="right"><parameter>relation</parameter>&nbsp;:</entry>
<entry>a <link linkend="GRelation">GRelation</link>.


</entry></row>
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<refsect2>
<title><anchor id="GTuples">struct GTuples</title>
<programlisting>struct GTuples
{
  guint len;
};
</programlisting>
<para>
The <link linkend="GTuples">GTuples</link> struct is used to return records (or tuples) from the
<link linkend="GRelation">GRelation</link> by <link linkend="g-relation-select">g_relation_select</link>().
It only contains one public member - the number of records that matched.
To access the matched records, you must use <link linkend="g-tuples-index">g_tuples_index</link>().
</para><informaltable pgwide="1" frame="none" role="struct">
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<row>
<entry><link linkend="guint">guint</link> <structfield>len</structfield></entry>
<entry>the number of records that matched.

</entry>
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<title><anchor id="g-tuples-destroy">g_tuples_destroy ()</title>
<programlisting>void        g_tuples_destroy                (<link linkend="GTuples">GTuples</link> *tuples);</programlisting>
<para>
Frees the records which were returned by <link linkend="g-relation-select">g_relation_select</link>().
This should always be called after <link linkend="g-relation-select">g_relation_select</link>() when you are
finished with the records.
The records are not removed from the <link linkend="GRelation">GRelation</link>.
</para><informaltable pgwide="1" frame="none" role="params">
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<row><entry align="right"><parameter>tuples</parameter>&nbsp;:</entry>
<entry>the tuple data to free.


</entry></row>
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<title><anchor id="g-tuples-index">g_tuples_index ()</title>
<programlisting><link linkend="gpointer">gpointer</link>    g_tuples_index                  (<link linkend="GTuples">GTuples</link> *tuples,
                                             <link linkend="gint">gint</link> index,
                                             <link linkend="gint">gint</link> field);</programlisting>
<para>
Gets a field from the records returned by <link linkend="g-relation-select">g_relation_select</link>().
It returns the given field of the record at the given index.
The returned value should not be changed.
</para><informaltable pgwide="1" frame="none" role="params">
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<row><entry align="right"><parameter>tuples</parameter>&nbsp;:</entry>
<entry>the tuple data, returned by <link linkend="g-relation-select">g_relation_select</link>().
</entry></row>
<row><entry align="right"><parameter>index</parameter>&nbsp;:</entry>
<entry>the index of the record.
</entry></row>
<row><entry align="right"><parameter>field</parameter>&nbsp;:</entry>
<entry>the field to return.
</entry></row>
<row><entry align="right"><emphasis>Returns</emphasis> :</entry><entry>the field of the record.


</entry></row>
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