104 lines
3.8 KiB
XML
104 lines
3.8 KiB
XML
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<chapter id="querysql">
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<title>Native SQL Queries</title>
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<para>
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You may also express queries in the native SQL dialect of your database. This is useful if you
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want to utilize database specific features such as the CONNECT keyword in Oracle.
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This also allows for a cleaner migration path from a direct SQL/JDBC based application to
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Hibernate.
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</para>
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<sect1 id="querysql-creating">
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<title>Creating a SQL based <literal>Query</literal></title>
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<para>
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SQL queries are exposed through the same <literal>Query</literal> interface, just like ordinary
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HQL queries. The only difference is the use of <literal>Session.createSQLQuery()</literal>.
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</para>
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<programlisting><![CDATA[Query sqlQuery = sess.createSQLQuery("select {cat.*} from cats {cat}", "cat", Cat.class);
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sqlQuery.setMaxResults(50);
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List cats = sqlQuery.list();]]></programlisting>
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<para>
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The three parameters provided to <literal>createSQLQuery()</literal> are:
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</para>
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<itemizedlist>
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<listitem>
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<para>
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the SQL query string
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</para>
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</listitem>
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<listitem>
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<para>
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a table alias name
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</para>
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</listitem>
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<listitem>
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<para>
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the persistent class returned by the query
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</para>
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</listitem>
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</itemizedlist>
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<para>
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The alias name is used inside the sql string to refer to the properties of the mapped class
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(in this case <literal>Cat</literal>). You may retrieve multiple objects per row by supplying
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a <literal>String</literal> array of alias names and a <literal>Class</literal> array of
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corresponding classes.
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</para>
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</sect1>
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<sect1 id="querysql-aliasreferences">
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<title>Alias and property references</title>
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<para>
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The <literal>{cat.*}</literal> notation used above is a shorthand for "all properties". You
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may even list the properties explicity, but you must let Hibernate provide SQL column aliases
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for each property. The placeholders for these column aliases are the property name qualified by
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the table alias. In the following example, we retrieve <literal>Cat</literal>s from a different
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table (<literal>cat_log</literal>) to the one declared in the mapping metadata. Notice that we
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may even use the property aliases in the where clause.
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</para>
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<programlisting><![CDATA[String sql = "select cat.originalId as {cat.id}, "
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+ " cat.mateid as {cat.mate}, cat.sex as {cat.sex}, "
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+ " cat.weight*10 as {cat.weight}, cat.name as {cat.name}"
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+ " from cat_log cat where {cat.mate} = :catId"
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List loggedCats = sess.createSQLQuery(sql, "cat", Cat.class)
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.setLong("catId", catId)
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.list();
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]]></programlisting>
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<para>
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<emphasis>Note:</emphasis> if you list each property explicitly, you must include all
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properties of the class <emphasis>and its subclasses</emphasis>!
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</para>
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</sect1>
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<sect1 id="querysql-namedqueries">
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<title>Named SQL queries</title>
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<para>
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Named SQL queries may be defined in the mapping document and called in exactly the same way
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as a named HQL query.
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</para>
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<programlisting><![CDATA[List people = sess.getNamedQuery("mySqlQuery")
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.setMaxResults(50)
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.list();]]></programlisting>
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<programlisting><![CDATA[<sql-query name="mySqlQuery">
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<return alias="person" class="eg.Person"/>
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SELECT {person}.NAME AS {person.name},
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{person}.AGE AS {person.age},
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{person}.SEX AS {person.sex}
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FROM PERSON {person} WHERE {person}.NAME LIKE 'Hiber%'
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</sql-query>]]></programlisting>
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</sect1>
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</chapter>
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