hibernate-orm/reference/en/modules/query_sql.xml

<?xml version="1.0" encoding="ISO-8859-1"?>
<chapter id="querysql" revision="2">
  <title>Native SQL</title>

  <para>You may also express queries in the native SQL dialect of your
  database. This is useful if you want to utilize database specific features
  such as query hints or the <literal>CONNECT</literal> keyword in Oracle. It
  also provides a clean migration path from a direct SQL/JDBC based
  application to Hibernate.</para>

  <para>Hibernate3 allows you to specify handwritten SQL (including stored
  procedures) for all create, update, delete, and load operations.</para>

  <sect1 id="querysql-creating" revision="3">
    <title>Using a <literal>SQLQuery</literal></title>

    <para>Execution of native SQL queries is controlled via the
    <literal>SQLQuery</literal> interface, which is obtained by calling
    <literal>Session.createSQLQuery()</literal>. In extremely simple cases, we
    can use the following form:</para>

    <programlisting>List cats = sess.createSQLQuery("select * from cats")
    .addEntity(Cat.class)
    .list();</programlisting>

    <para>This query specified:</para>

    <itemizedlist>
      <listitem>
        <para>the SQL query string</para>
      </listitem>

      <listitem>
        <para>the entity returned by the query</para>
      </listitem>
    </itemizedlist>

    <para>Here, the result set column names are assumed to be the same as the
    column names specified in the mapping document. This can be problematic
    for SQL queries which join multiple tables, since the same column names
    may appear in more than one table. The following form is not vulnerable to
    column name duplication:</para>

    <programlisting>List cats = sess.createSQLQuery("select {cat.*} from cats cat")
    .addEntity("cat", Cat.class)
    .list();</programlisting>

    <para>This query specified:</para>

    <itemizedlist>
      <listitem>
        <para>the SQL query string, with a placeholder for Hibernate to inject
        the column aliases</para>
      </listitem>

      <listitem>
        <para>the entity returned by the query, and its SQL table alias</para>
      </listitem>
    </itemizedlist>

    <para>The <literal>addEntity()</literal> method associates the SQL table
    alias with the returned entity class, and determines the shape of the
    query result set.</para>

    <para>The <literal>addJoin()</literal> method may be used to load
    associations to other entities and collections.</para>

    <programlisting>List cats = sess.createSQLQuery(
        "select {cat.*}, {kitten.*} from cats cat, cats kitten where kitten.mother = cat.id"
    )
    .addEntity("cat", Cat.class)
    .addJoin("kitten", "cat.kittens")
    .list();</programlisting>

    <para>A native SQL query might return a simple scalar value or a
    combination of scalars and entities.</para>

    <programlisting>Double max = (Double) sess.createSQLQuery("select max(cat.weight) as maxWeight from cats cat")
        .addScalar("maxWeight", Hibernate.DOUBLE);
        .uniqueResult();</programlisting>

    <para>You can alternatively describe the resultset mapping informations in
    your hbm files and use them for your queries</para>

    <programlisting>List cats = sess.createSQLQuery(
        "select {cat.*}, {kitten.*} from cats cat, cats kitten where kitten.mother = cat.id"
    )
    .setResultSetMapping("catAndKitten")
    .list();</programlisting>
  </sect1>

  <sect1 id="querysql-aliasreferences">
    <title>Alias and property references</title>

    <para>The <literal>{cat.*}</literal> notation used above is a shorthand
    for "all properties". Alternatively, you may list the columns explicity,
    but even this case we let Hibernate inject the SQL column aliases for each
    property. The placeholder for a column alias is just the property name
    qualified by the table alias. In the following example, we retrieve
    <literal>Cat</literal>s from a different table
    (<literal>cat_log</literal>) to the one declared in the mapping metadata.
    Notice that we may even use the property aliases in the where clause if we
    like.</para>

    <para>The <literal>{}</literal>-syntax is <emphasis>not</emphasis>
    required for named queries. See <xref
    linkend="querysql-namedqueries" /></para>

    <programlisting>String sql = "select cat.originalId as {cat.id}, " +
    "cat.mateid as {cat.mate}, cat.sex as {cat.sex}, " +
    "cat.weight*10 as {cat.weight}, cat.name as {cat.name} " +
    "from cat_log cat where {cat.mate} = :catId"
    
List loggedCats = sess.createSQLQuery(sql)
    .addEntity("cat", Cat.class)
    .setLong("catId", catId)
    .list();</programlisting>

    <para><emphasis>Note:</emphasis> if you list each property explicitly, you
    must include all properties of the class <emphasis>and its
    subclasses</emphasis>!</para>

    <para>The following table shows the different possibilities of using the
    alias injection. Note: the alias names in the result are examples, each
    alias will have a unique and probably different name when used.</para>

    <table frame="topbot" id="aliasinjection-summary">
      <title>Alias injection names</title>

      <tgroup cols="4">
        <colspec colwidth="1*" />

        <colspec colwidth="1*" />

        <colspec colwidth="2.5*" />

        <thead>
          <row>
            <entry>Description</entry>

            <entry>Syntax</entry>

            <entry>Example</entry>
          </row>
        </thead>

        <tbody>
          <row>
            <entry>A simple property</entry>

            <entry><literal>{[aliasname].[propertyname]</literal></entry>

            <entry><literal>A_NAME as {item.name}</literal></entry>
          </row>

          <row>
            <entry>A composite property</entry>

            <entry><literal>{[aliasname].[componentname].[propertyname]}</literal></entry>

            <entry><literal>CURRENCY as {item.amount.currency}, VALUE as
            {item.amount.value}</literal></entry>
          </row>

          <row>
            <entry>Discriminator of an entity</entry>

            <entry><literal>{[aliasname].class}</literal></entry>

            <entry><literal>DISC as {item.class}</literal></entry>
          </row>

          <row>
            <entry>All properties of an entity</entry>

            <entry><literal>{[aliasname].*}</literal></entry>

            <entry><literal>{item.*}</literal></entry>
          </row>

          <row>
            <entry>A collection key</entry>

            <entry><literal>{[aliasname].key}</literal></entry>

            <entry><literal>ORGID as {coll.key}</literal></entry>
          </row>

          <row>
            <entry>The id of an collection</entry>

            <entry><literal>{[aliasname].id}</literal></entry>

            <entry><literal>EMPID as {coll.id}</literal></entry>
          </row>

          <row>
            <entry>The element of an collection</entry>

            <entry><literal>{[aliasname].element}</literal></entry>

            <entry><literal>XID as {coll.element}</literal></entry>

            <entry></entry>
          </row>

          <row>
            <entry>Property of the element in the collection</entry>

            <entry><literal>{[aliasname].element.[propertyname]}</literal></entry>

            <entry><literal>NAME as {coll.element.name}</literal></entry>
          </row>

          <row>
            <entry>All properties of the element in the collection</entry>

            <entry><literal>{[aliasname].element.*}</literal></entry>

            <entry><literal>{coll.element.*}</literal></entry>
          </row>

          <row>
            <entry>All properties of the the collection</entry>

            <entry><literal>{[aliasname].*}</literal></entry>

            <entry><literal>{coll.*}</literal></entry>
          </row>
        </tbody>
      </tgroup>
    </table>
  </sect1>

  <sect1 id="querysql-namedqueries" revision="3">
    <title>Named SQL queries</title>

    <para>Named SQL queries may be defined in the mapping document and called
    in exactly the same way as a named HQL query. In this case, we do
    <emphasis>not</emphasis> need to call
    <literal>addEntity()</literal>.</para>

    <programlisting>&lt;sql-query name="persons"&gt;
    &lt;return alias="person" class="eg.Person"/&gt;
    SELECT person.NAME AS {person.name},
           person.AGE AS {person.age},
           person.SEX AS {person.sex}
    FROM PERSON person 
    WHERE person.NAME LIKE :namePattern
&lt;/sql-query&gt;</programlisting>

    <programlisting>List people = sess.getNamedQuery("persons")
    .setString("namePattern", namePattern)
    .setMaxResults(50)
    .list();</programlisting>

    <para>The <literal>&lt;return-join&gt;</literal> and
    <literal>&lt;load-collection&gt;</literal> elements are used to join
    associations and define queries which initialize collections,
    respectively.</para>

    <programlisting>&lt;sql-query name="personsWith"&gt;
    &lt;return alias="person" class="eg.Person"/&gt;
    &lt;return-join alias="address" property="person.mailingAddress"/&gt;
    SELECT person.NAME AS {person.name},
           person.AGE AS {person.age},
           person.SEX AS {person.sex},
           adddress.STREET AS {address.street},
           adddress.CITY AS {address.city},
           adddress.STATE AS {address.state},
           adddress.ZIP AS {address.zip}
    FROM PERSON person 
    JOIN ADDRESS adddress
        ON person.ID = address.PERSON_ID AND address.TYPE='MAILING'
    WHERE person.NAME LIKE :namePattern
&lt;/sql-query&gt;</programlisting>

    <para>A named SQL query may return a scalar value. You must specfy the
    column alias and Hibernate type using the
    <literal>&lt;return-scalar&gt;</literal> element:</para>

    <programlisting>&lt;sql-query name="mySqlQuery"&gt;
    &lt;return-scalar column="name" type="string"/&gt;
    &lt;return-scalar column="age" type="long"/&gt;
    SELECT p.NAME AS name,
           p.AGE AS age,
    FROM PERSON p WHERE p.NAME LIKE 'Hiber%'
&lt;/sql-query&gt;</programlisting>

    <para>You can externalize the resultset mapping informations in a
    <literal>&lt;resultset&gt;</literal> element to either reuse them accross
    several named queries or through the
    <literal>setResultSetMapping()</literal> API.</para>

    <programlisting>&lt;resultset name="personAddress"&gt;
    &lt;return alias="person" class="eg.Person"/&gt;
    &lt;return-join alias="address" property="person.mailingAddress"/&gt;
&lt;/resultset&gt;

&lt;sql-query name="personsWith" resultset-ref="personAddress"&gt;
    SELECT person.NAME AS {person.name},
           person.AGE AS {person.age},
           person.SEX AS {person.sex},
           adddress.STREET AS {address.street},
           adddress.CITY AS {address.city},
           adddress.STATE AS {address.state},
           adddress.ZIP AS {address.zip}
    FROM PERSON person 
    JOIN ADDRESS adddress
        ON person.ID = address.PERSON_ID AND address.TYPE='MAILING'
    WHERE person.NAME LIKE :namePattern
&lt;/sql-query&gt;</programlisting>

    <sect2 id="propertyresults">
      <title>Using return-property to explicitly specify column/alias
      names</title>

      <para>With <literal>&lt;return-property&gt;</literal> you can explicitly
      tell Hibernate what column aliases to use, instead of using the
      <literal>{}</literal>-syntax to let Hibernate inject its own
      aliases.</para>

      <programlisting>&lt;sql-query name="mySqlQuery"&gt;
    &lt;return alias="person" class="eg.Person"&gt;
        &lt;return-property name="name" column="myName"/&gt;
        &lt;return-property name="age" column="myAge"/&gt;
        &lt;return-property name="sex" column="mySex"/&gt;
    &lt;/return&gt;
    SELECT person.NAME AS myName,
           person.AGE AS myAge,
           person.SEX AS mySex,
    FROM PERSON person WHERE person.NAME LIKE :name
&lt;/sql-query&gt;
</programlisting>

      <para><literal>&lt;return-property&gt;</literal> also works with
      multiple columns. This solves a limitation with the
      <literal>{}</literal>-syntax which can not allow fine grained control of
      multi-column properties.</para>

      <programlisting>&lt;sql-query name="organizationCurrentEmployments"&gt;
    &lt;return alias="emp" class="Employment"&gt;            
        &lt;return-property name="salary"&gt; 
            &lt;return-column name="VALUE"/&gt;
            &lt;return-column name="CURRENCY"/&gt;            
        &lt;/return-property&gt;
        &lt;return-property name="endDate" column="myEndDate"/&gt;
    &lt;/return&gt;
        SELECT EMPLOYEE AS {emp.employee}, EMPLOYER AS {emp.employer}, 
        STARTDATE AS {emp.startDate}, ENDDATE AS {emp.endDate},
        REGIONCODE as {emp.regionCode}, EID AS {emp.id}, VALUE, CURRENCY
        FROM EMPLOYMENT
        WHERE EMPLOYER = :id AND ENDDATE IS NULL
        ORDER BY STARTDATE ASC
&lt;/sql-query&gt;</programlisting>

      <para>Notice that in this example we used
      <literal>&lt;return-property&gt;</literal> in combination with the
      <literal>{}</literal>-syntax for injection. Allowing users to choose how
      they want to refer column and properties.</para>

      <para>If your mapping has a discriminator you must use
      <literal>&lt;return-discriminator&gt;</literal> to specify the
      discriminator column.</para>
    </sect2>

    <sect2 id="sp_query">
      <title>Using stored procedures for querying</title>

      <para>Hibernate 3 introduces support for queries via stored procedures.
      The stored procedures must return a resultset as the first out-parameter
      to be able to work with Hibernate. An example of such a stored procedure
      in Oracle 9 and higher is as follows:</para>

      <programlisting>CREATE OR REPLACE FUNCTION selectAllEmployments 
    RETURN SYS_REFCURSOR 
AS 
    st_cursor SYS_REFCURSOR; 
BEGIN 
    OPEN st_cursor FOR 
 SELECT EMPLOYEE, EMPLOYER, 
 STARTDATE, ENDDATE, 
 REGIONCODE, EID, VALUE, CURRENCY 
 FROM EMPLOYMENT; 
      RETURN  st_cursor; 
 END;</programlisting>

      <para>To use this query in Hibernate you need to map it via a named
      query.</para>

      <programlisting>&lt;sql-query name="selectAllEmployees_SP" callable="true"&gt;
    &lt;return alias="emp" class="Employment"&gt;
        &lt;return-property name="employee" column="EMPLOYEE"/&gt;
        &lt;return-property name="employer" column="EMPLOYER"/&gt;            
        &lt;return-property name="startDate" column="STARTDATE"/&gt;
        &lt;return-property name="endDate" column="ENDDATE"/&gt;            
        &lt;return-property name="regionCode" column="REGIONCODE"/&gt;            
        &lt;return-property name="id" column="EID"/&gt;                        
        &lt;return-property name="salary"&gt; 
            &lt;return-column name="VALUE"/&gt;
            &lt;return-column name="CURRENCY"/&gt;            
        &lt;/return-property&gt;
    &lt;/return&gt;
    { ? = call selectAllEmployments() }
&lt;/sql-query&gt;</programlisting>

      <para>Notice stored procedures currently only return scalars and
      entities. <literal>&lt;return-join&gt;</literal> and
      <literal>&lt;load-collection&gt;</literal> are not supported.</para>

      <sect3 id="querysql-limits-storedprocedures">
        <title>Rules/limitations for using stored procedures</title>

        <para>To use stored procedures with Hibernate the procedures have to
        follow some rules. If they do not follow those rules they are not
        usable with Hibernate. If you still want to use these procedures you
        have to execute them via <literal>session.connection()</literal>. The
        rules are different for each database, since database vendors have
        different stored procedure semantics/syntax.</para>

        <para>Stored procedure queries can't be paged with
        <literal>setFirstResult()/setMaxResults()</literal>.</para>

        <para>For Oracle the following rules apply:</para>

        <itemizedlist spacing="compact">
          <listitem>
            <para>The procedure must return a result set. This is done by
            returning a <literal>SYS_REFCURSOR</literal> in Oracle 9 or 10. In
            Oracle you need to define a <literal>REF CURSOR</literal>
            type.</para>
          </listitem>

          <listitem>
            <para>Recommended form is <literal>{ ? = call
            procName(&lt;parameters&gt;) }</literal> or <literal>{ ? = call
            procName }</literal> (this is more an Oracle rule than a Hibernate
            rule).</para>
          </listitem>
        </itemizedlist>

        <para>For Sybase or MS SQL server the following rules apply:</para>

        <itemizedlist spacing="compact">
          <listitem>
            <para>The procedure must return a result set. Note that since
            these servers can/will return multiple result sets and update
            counts, Hibernate will iterate the results and take the first
            result that is a result set as its return value. Everything else
            will be discarded.</para>
          </listitem>

          <listitem>
            <para>If you can enable <literal>SET NOCOUNT ON</literal> in your
            procedure it will probably be more efficient, but this is not a
            requirement.</para>
          </listitem>
        </itemizedlist>
      </sect3>
    </sect2>
  </sect1>

  <sect1 id="querysql-cud">
    <title>Custom SQL for create, update and delete</title>

    <para>Hibernate3 can use custom SQL statements for create, update, and
    delete operations. The class and collection persisters in Hibernate
    already contain a set of configuration time generated strings (insertsql,
    deletesql, updatesql etc.). The mapping tags
    <literal>&lt;sql-insert&gt;</literal>,
    <literal>&lt;sql-delete&gt;</literal>, and
    <literal>&lt;sql-update&gt;</literal> override these strings:</para>

    <programlisting>&lt;class name="Person"&gt;
    &lt;id name="id"&gt;
        &lt;generator class="increment"/&gt;
    &lt;/id&gt;
    &lt;property name="name" not-null="true"/&gt;
    &lt;sql-insert&gt;INSERT INTO PERSON (NAME, ID) VALUES ( UPPER(?), ? )&lt;/sql-insert&gt;
    &lt;sql-update&gt;UPDATE PERSON SET NAME=UPPER(?) WHERE ID=?&lt;/sql-update&gt;
    &lt;sql-delete&gt;DELETE FROM PERSON WHERE ID=?&lt;/sql-delete&gt;
&lt;/class&gt;</programlisting>

    <para>The SQL is directly executed in your database, so you are free to
    use any dialect you like. This will of course reduce the portability of
    your mapping if you use database specific SQL.</para>

    <para>Stored procedures are supported if the <literal>callable</literal>
    attribute is set:</para>

    <programlisting>&lt;class name="Person"&gt;
    &lt;id name="id"&gt;
        &lt;generator class="increment"/&gt;
    &lt;/id&gt;
    &lt;property name="name" not-null="true"/&gt;
    &lt;sql-insert callable="true"&gt;{call createPerson (?, ?)}&lt;/sql-insert&gt;
    &lt;sql-delete callable="true"&gt;{? = call deletePerson (?)}&lt;/sql-delete&gt;
    &lt;sql-update callable="true"&gt;{? = call updatePerson (?, ?)}&lt;/sql-update&gt;
&lt;/class&gt;</programlisting>

    <para>The order of the positional parameters are currently vital, as they
    must be in the same sequence as Hibernate expects them.</para>

    <para>You can see the expected order by enabling debug logging for the
    <literal>org.hibernate.persister.entity</literal> level. With this level
    enabled Hibernate will print out the static SQL that is used to create,
    update, delete etc. entities. (To see the expected sequence, remember to
    not include your custom SQL in the mapping files as that will override the
    Hibernate generated static sql.)</para>

    <para>The stored procedures are in most cases (read: better do it than
    not) required to return the number of rows inserted/updated/deleted, as
    Hibernate has some runtime checks for the success of the statement.
    Hibernate always registers the first statement parameter as a numeric
    output parameter for the CUD operations:</para>

    <programlisting>CREATE OR REPLACE FUNCTION updatePerson (uid IN NUMBER, uname IN VARCHAR2)
    RETURN NUMBER IS
BEGIN

    update PERSON
    set
        NAME = uname,
    where
        ID = uid;

    return SQL%ROWCOUNT;

END updatePerson;</programlisting>
  </sect1>

  <sect1 id="querysql-load">
    <title>Custom SQL for loading</title>

    <para>You may also declare your own SQL (or HQL) queries for entity
    loading:</para>

    <programlisting>&lt;sql-query name="person"&gt;
    &lt;return alias="pers" class="Person" lock-mode="upgrade"/&gt;
    SELECT NAME AS {pers.name}, ID AS {pers.id} 
    FROM PERSON 
    WHERE ID=? 
    FOR UPDATE
&lt;/sql-query&gt;</programlisting>

    <para>This is just a named query declaration, as discussed earlier. You
    may reference this named query in a class mapping:</para>

    <programlisting>&lt;class name="Person"&gt;
    &lt;id name="id"&gt;
        &lt;generator class="increment"/&gt;
    &lt;/id&gt;
    &lt;property name="name" not-null="true"/&gt;
    &lt;loader query-ref="person"/&gt;
&lt;/class&gt;</programlisting>

    <para>This even works with stored procedures.</para>

    <para>You may even define a query for collection loading:</para>

    <programlisting>&lt;set name="employments" inverse="true"&gt;
    &lt;key/&gt;
    &lt;one-to-many class="Employment"/&gt;
    &lt;loader query-ref="employments"/&gt;
&lt;/set&gt;</programlisting>

    <programlisting>&lt;sql-query name="employments"&gt;
    &lt;load-collection alias="emp" role="Person.employments"/&gt;
    SELECT {emp.*}
    FROM EMPLOYMENT emp
    WHERE EMPLOYER = :id
    ORDER BY STARTDATE ASC, EMPLOYEE ASC
&lt;/sql-query&gt;</programlisting>

    <para>You could even define an entity loader that loads a collection by
    join fetching:</para>

    <programlisting>&lt;sql-query name="person"&gt;
    &lt;return alias="pers" class="Person"/&gt;
    &lt;return-join alias="emp" property="pers.employments"/&gt; 
    SELECT NAME AS {pers.*}, {emp.*}
    FROM PERSON pers
    LEFT OUTER JOIN EMPLOYMENT emp 
        ON pers.ID = emp.PERSON_ID
    WHERE ID=?
&lt;/sql-query&gt;</programlisting>
  </sect1>
</chapter>