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## Chapter 18. Native SQL

You can 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 `CONNECT` keyword in Oracle. It also provides a clean migration path from a direct SQL/JDBC based application to Hibernate.

Hibernate3 allows you to specify handwritten SQL, including stored procedures, for all create, update, delete, and load operations.

## 18.1. Using a `SQLQuery`

Execution of native SQL queries is controlled via the `SQLQuery` interface, which is obtained by calling `Session.createSQLQuery()`. The following sections describe how to use this API for querying.

### 18.1.1. Scalar queries

The most basic SQL query is to get a list of scalars (values).

    sess.createSQLQuery("SELECT * FROM CATS").list();
    sess.createSQLQuery("SELECT ID, NAME, BIRTHDATE FROM CATS").list();

These will return a List of Object arrays (Object[]) with scalar values for each column in the CATS table. Hibernate will use ResultSetMetadata to deduce the actual order and types of the returned scalar values.

To avoid the overhead of using `ResultSetMetadata`, or simply to be more explicit in what is returned, one can use `addScalar()`:

    sess.createSQLQuery("SELECT * FROM CATS")
     .addScalar("ID", Hibernate.LONG)
     .addScalar("NAME", Hibernate.STRING)
     .addScalar("BIRTHDATE", Hibernate.DATE)

This query specified:

- the SQL query string

- the columns and types to return

This will return Object arrays, but now it will not use `ResultSetMetadata` but will instead explicitly get the ID, NAME and BIRTHDATE column as respectively a Long, String and a Short from the underlying resultset. This also means that only these three columns will be returned, even though the query is using `*` and could return more than the three listed columns.

It is possible to leave out the type information for all or some of the scalars.

    sess.createSQLQuery("SELECT * FROM CATS")
     .addScalar("ID", Hibernate.LONG)
     .addScalar("NAME")
     .addScalar("BIRTHDATE")

This is essentially the same query as before, but now `ResultSetMetaData` is used to determine the type of NAME and BIRTHDATE, where as the type of ID is explicitly specified.

How the java.sql.Types returned from ResultSetMetaData is mapped to Hibernate types is controlled by the Dialect. If a specific type is not mapped, or does not result in the expected type, it is possible to customize it via calls to `registerHibernateType` in the Dialect.

### 18.1.2. Entity queries

The above queries were all about returning scalar values, basically returning the "raw" values from the resultset. The following shows how to get entity objects from a native sql query via `addEntity()`.

    sess.createSQLQuery("SELECT * FROM CATS").addEntity(Cat.class);
    sess.createSQLQuery("SELECT ID, NAME, BIRTHDATE FROM CATS").addEntity(Cat.class);

This query specified:

- the SQL query string

- the entity returned by the query

Assuming that Cat is mapped as a class with the columns ID, NAME and BIRTHDATE the above queries will both return a List where each element is a Cat entity.

If the entity is mapped with a `many-to-one` to another entity it is required to also return this when performing the native query, otherwise a database specific "column not found" error will occur. The additional columns will automatically be returned when using the * notation, but we prefer to be explicit as in the following example for a `many-to-one` to a `Dog`:

    sess.createSQLQuery("SELECT ID, NAME, BIRTHDATE, DOG_ID FROM CATS").addEntity(Cat.class);

This will allow cat.getDog() to function properly.

### 18.1.3. Handling associations and collections

It is possible to eagerly join in the `Dog` to avoid the possible extra roundtrip for initializing the proxy. This is done via the `addJoin()` method, which allows you to join in an association or collection.

    sess.createSQLQuery("SELECT c.ID, NAME, BIRTHDATE, DOG_ID, D_ID, D_NAME FROM CATS c, DOGS d WHERE c.DOG_ID = d.D_ID")
     .addEntity("cat", Cat.class)
     .addJoin("cat.dog");

In this example, the returned `Cat`'s will have their `dog` property fully initialized without any extra roundtrip to the database. Notice that you added an alias name ("cat") to be able to specify the target property path of the join. It is possible to do the same eager joining for collections, e.g. if the `Cat` had a one-to-many to `Dog` instead.

    sess.createSQLQuery("SELECT ID, NAME, BIRTHDATE, D_ID, D_NAME, CAT_ID FROM CATS c, DOGS d WHERE c.ID = d.CAT_ID")
     .addEntity("cat", Cat.class)
     .addJoin("cat.dogs");

At this stage you are reaching the limits of what is possible with native queries, without starting to enhance the sql queries to make them usable in Hibernate. Problems can arise when returning multiple entities of the same type or when the default alias/column names are not enough.

### 18.1.4. Returning multiple entities

Until now, 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 that join multiple tables, since the same column names can appear in more than one table.

Column alias injection is needed in the following query (which most likely will fail):

    sess.createSQLQuery("SELECT c.*, m.*  FROM CATS c, CATS m WHERE c.MOTHER_ID = c.ID")
     .addEntity("cat", Cat.class)
     .addEntity("mother", Cat.class)

The query was intended to return two Cat instances per row: a cat and its mother. The query will, however, fail because there is a conflict of names; the instances are mapped to the same column names. Also, on some databases the returned column aliases will most likely be on the form "c.ID", "c.NAME", etc. which are not equal to the columns specified in the mappings ("ID" and "NAME").

The following form is not vulnerable to column name duplication:

    sess.createSQLQuery("SELECT {cat.*}, {m.*}  FROM CATS c, CATS m WHERE c.MOTHER_ID = m.ID")
     .addEntity("cat", Cat.class)
     .addEntity("mother", Cat.class)

This query specified:

- the SQL query string, with placeholders for Hibernate to inject column aliases

- the entities returned by the query

The {cat.*} and {mother.*} notation used above is a shorthand for "all properties". Alternatively, you can list the columns explicitly, but even in this case Hibernate injects 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, you retrieve Cats and their mothers from a different table (cat_log) to the one declared in the mapping metadata. You can even use the property aliases in the where clause.

    String sql = "SELECT ID as {c.id}, NAME as {c.name}, " +
             "BIRTHDATE as {c.birthDate}, MOTHER_ID as {c.mother}, {mother.*} " +
             "FROM CAT_LOG c, CAT_LOG m WHERE {c.mother} = c.ID";

    List loggedCats = sess.createSQLQuery(sql)
            .addEntity("cat", Cat.class)
            .addEntity("mother", Cat.class).list()

#### 18.1.4.1. Alias and property references

In most cases the above alias injection is needed. For queries relating to more complex mappings, like composite properties, inheritance discriminators, collections etc., you can use specific aliases that allow Hibernate to inject the proper aliases.

The following table shows the different ways you can use the alias injection. Please note that the alias names in the result are simply examples; each alias will have a unique and probably different name when used.

Table 18.1. Alias injection names

Description | Syntax | Example
--- | --- | ---
A simple property | `{[aliasname].[propertyname]` | `A_NAME as {item.name}`
A composite property | `{[aliasname].[componentname].[propertyname]}` | `CURRENCY as {item.amount.currency}, VALUE as {item.amount.value}`
Discriminator of an entity | `{[aliasname].class}` | `DISC as {item.class}`
All properties of an entity | `{[aliasname].*}` | `{item.*}`
A collection key | `{[aliasname].key}` | `ORGID as {coll.key}`
The id of an collection | `{[aliasname].id}` | `EMPID as {coll.id}`
The element of an collection | `{[aliasname].element}` | `XID as {coll.element}`
property of the element in the collection | `{[aliasname].element.[propertyname]}` | `NAME as {coll.element.name}`
All properties of the element in the collection | `{[aliasname].element.*}` | `{coll.element.*}`
All properties of the collection | `{[aliasname].*}` | `{coll.*}`

### 18.1.5. Returning non-managed entities

It is possible to apply a ResultTransformer to native SQL queries, allowing it to return non-managed entities.

    sess.createSQLQuery("SELECT NAME, BIRTHDATE FROM CATS")
            .setResultTransformer(Transformers.aliasToBean(CatDTO.class))

This query specified:

- the SQL query string

- a result transformer

The above query will return a list of `CatDTO` which has been instantiated and injected the values of NAME and BIRTHNAME into its corresponding properties or fields.

### 18.1.6. Handling inheritance

Native SQL queries which query for entities that are mapped as part of an inheritance must include all properties for the baseclass and all its subclasses.

### 18.1.7. Parameters

Native SQL queries support positional as well as named parameters:

    Query query = sess.createSQLQuery("SELECT * FROM CATS WHERE NAME like ?").addEntity(Cat.class);
    List pusList = query.setString(0, "Pus%").list();

    query = sess.createSQLQuery("SELECT * FROM CATS WHERE NAME like :name").addEntity(Cat.class);
    List pusList = query.setString("name", "Pus%").list();

## 18.2. Named SQL queries

Named SQL queries can also be defined in the mapping document and called in exactly the same way as a named HQL query (see Section 11.4.1.7, “Externalizing named queries”). In this case, you do not need to call `addEntity()`.

Example 18.1. Named sql query using the <sql-query> maping element

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

Example 18.2. Execution of a named query

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

The `<return-join>` element is use to join associations and the `<load-collection>` element is used to define queries which initialize collections,

Example 18.3. Named sql query with association

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

A named SQL query may return a scalar value. You must declare the column alias and Hibernate type using the `<return-scalar>` element:

Example 18.4. Named query returning a scalar

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

You can externalize the resultset mapping information in a `<resultset>` element which will allow you to either reuse them across several named queries or through the `setResultSetMapping()` API.

Example 18.5. <resultset> mapping used to externalize mapping information

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

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

You can, alternatively, use the resultset mapping information in your hbm files directly in java code.

Example 18.6. Programmatically specifying the result mapping information

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

So far we have only looked at externalizing SQL queries using Hibernate mapping files. The same concept is also available with anntations and is called named native queries. You can use `@NamedNativeQuery` (`@NamedNativeQueries`) in conjunction with `@SqlResultSetMapping` (`@SqlResultSetMappings`). Like `@NamedQuery`, `@NamedNativeQuery` and `@SqlResultSetMapping` can be defined at class level, but their scope is global to the application. Lets look at a view examples.

Example 18.7, “Named SQL query using `@NamedNativeQuery` together with `@SqlResultSetMapping`” shows how a `resultSetMapping` parameter is defined in `@NamedNativeQuery`. It represents the name of a defined `@SqlResultSetMapping`. The resultset mapping declares the entities retrieved by this native query. Each field of the entity is bound to an SQL alias (or column name). All fields of the entity including the ones of subclasses and the foreign key columns of related entities have to be present in the SQL query. Field definitions are optional provided that they map to the same column name as the one declared on the class property. In the example 2 entities, `Night` and `Area`, are returned and each property is declared and associated to a column name, actually the column name retrieved by the query.

In Example 18.8, “Implicit result set mapping” the result set mapping is implicit. We only describe the entity class of the result set mapping. The property / column mappings is done using the entity mapping values. In this case the model property is bound to the model_txt column.

Finally, if the association to a related entity involve a composite primary key, a `@FieldResult` element should be used for each foreign key column. The `@FieldResult` name is composed of the property name for the relationship, followed by a dot ("."), followed by the name or the field or property of the primary key. This can be seen in Example 18.9, “Using dot notation in @FieldResult for specifying associations ”.

Example 18.7. Named SQL query using `@NamedNativeQuery` together with `@SqlResultSetMapping`

    @NamedNativeQuery(name="night&area", query="select night.id nid, night.night_duration, "

        + " night.night_date, area.id aid, night.area_id, area.name "

        + "from Night night, Area area where night.area_id = area.id",

                      resultSetMapping="joinMapping")

    @SqlResultSetMapping(name="joinMapping", entities={

        @EntityResult(entityClass=Night.class, fields = {

            @FieldResult(name="id", column="nid"),

            @FieldResult(name="duration", column="night_duration"),

            @FieldResult(name="date", column="night_date"),

            @FieldResult(name="area", column="area_id"),

            discriminatorColumn="disc"

        }),

        @EntityResult(entityClass=org.hibernate.test.annotations.query.Area.class, fields = {

            @FieldResult(name="id", column="aid"),

            @FieldResult(name="name", column="name")

        })

        }

    )

Example 18.8. Implicit result set mapping

    @Entity

    @SqlResultSetMapping(name="implicit",

                         entities=@EntityResult(entityClass=SpaceShip.class))

    @NamedNativeQuery(name="implicitSample",

                      query="select * from SpaceShip",

                      resultSetMapping="implicit")

    public class SpaceShip {

        private String name;

        private String model;

        private double speed;

        @Id

        public String getName() {

            return name;

        }

        public void setName(String name) {

            this.name = name;

        }

        @Column(name="model_txt")

        public String getModel() {

            return model;

        }

        public void setModel(String model) {

            this.model = model;

        }

        public double getSpeed() {

            return speed;

        }

        public void setSpeed(double speed) {

            this.speed = speed;

        }

    }

Example 18.9. Using dot notation in @FieldResult for specifying associations

    @Entity

    @SqlResultSetMapping(name="compositekey",

            entities=@EntityResult(entityClass=SpaceShip.class,

                fields = {

                        @FieldResult(name="name", column = "name"),

                        @FieldResult(name="model", column = "model"),

                        @FieldResult(name="speed", column = "speed"),

                        @FieldResult(name="captain.firstname", column = "firstn"),

                        @FieldResult(name="captain.lastname", column = "lastn"),

                        @FieldResult(name="dimensions.length", column = "length"),

                        @FieldResult(name="dimensions.width", column = "width")

                        }),

            columns = { @ColumnResult(name = "surface"),

                        @ColumnResult(name = "volume") } )

    @NamedNativeQuery(name="compositekey",

        query="select name, model, speed, lname as lastn, fname as firstn, length, width, length * width as surface from SpaceShip",

        resultSetMapping="compositekey")

    } )

    public class SpaceShip {

        private String name;

        private String model;

        private double speed;

        private Captain captain;

        private Dimensions dimensions;

        @Id

        public String getName() {

            return name;

        }

        public void setName(String name) {

            this.name = name;

        }

        @ManyToOne(fetch= FetchType.LAZY)

        @JoinColumns( {

                @JoinColumn(name="fname", referencedColumnName = "firstname"),

                @JoinColumn(name="lname", referencedColumnName = "lastname")

                } )

        public Captain getCaptain() {

            return captain;

        }

        public void setCaptain(Captain captain) {

            this.captain = captain;

        }

        public String getModel() {

            return model;

        }

        public void setModel(String model) {

            this.model = model;

        }

        public double getSpeed() {

            return speed;

        }

        public void setSpeed(double speed) {

            this.speed = speed;

        }

        public Dimensions getDimensions() {

            return dimensions;

        }

        public void setDimensions(Dimensions dimensions) {

            this.dimensions = dimensions;

        }

    }

    @Entity

    @IdClass(Identity.class)

    public class Captain implements Serializable {

        private String firstname;

        private String lastname;

        @Id

        public String getFirstname() {

            return firstname;

        }

        public void setFirstname(String firstname) {

            this.firstname = firstname;

        }

        @Id

        public String getLastname() {

            return lastname;

        }

        public void setLastname(String lastname) {

            this.lastname = lastname;

        }

    }

## Tip

If you retrieve a single entity using the default mapping, you can specify the `resultClass` attribute instead of `resultSetMapping`:

    @NamedNativeQuery(name="implicitSample", query="select * from SpaceShip", resultClass=SpaceShip.class)

    public class SpaceShip {

In some of your native queries, you'll have to return scalar values, for example when building report queries. You can map them in the `@SqlResultsetMapping` through `@ColumnResult`. You actually can even mix, entities and scalar returns in the same native query (this is probably not that common though).

Example 18.10. Scalar values via `@ColumnResult`

    @SqlResultSetMapping(name="scalar", columns=@ColumnResult(name="dimension"))

    @NamedNativeQuery(name="scalar", query="select length*width as dimension from SpaceShip", resultSetMapping="scalar")

An other query hint specific to native queries has been introduced: `org.hibernate.callable` which can be true or false depending on whether the query is a stored procedure or not.

### 18.2.1. Using return-property to explicitly specify column/alias names

You can explicitly tell Hibernate what column aliases to use with `<return-property>`, instead of using the `{}`-syntax to let Hibernate inject its own aliases.For example:

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

`<return-property>` also works with multiple columns. This solves a limitation with the `{}`-syntax which cannot allow fine grained control of multi-column properties.

    <sql-query name="organizationCurrentEmployments">
        <return alias="emp" class="Employment">
            <return-property name="salary">
                <return-column name="VALUE"/>
                <return-column name="CURRENCY"/>
            </return-property>
            <return-property name="endDate" column="myEndDate"/>
        </return>
            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
    </sql-query>

In this example `<return-property>` was used in combination with the `{}`-syntax for injection. This allows users to choose how they want to refer column and properties.

If your mapping has a discriminator you must use `<return-discriminator>` to specify the discriminator column.

### 18.2.2. Using stored procedures for querying

Hibernate3 provides support for queries via stored procedures and functions. Most of the following documentation is equivalent for both. The stored procedure/function must return a resultset as the first out-parameter to be able to work with Hibernate. An example of such a stored function in Oracle 9 and higher is as follows:

    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;

To use this query in Hibernate you need to map it via a named query.

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

Stored procedures currently only return scalars and entities. `<return-join>` and `<load-collection>` are not supported.

#### 18.2.2.1. Rules/limitations for using stored procedures

You cannot use stored procedures with Hibernate unless you follow some procedure/function 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 `session.connection()`. The rules are different for each database, since database vendors have different stored procedure semantics/syntax.

Stored procedure queries cannot be paged with `setFirstResult()/setMaxResults()`.

The recommended call form is standard SQL92: `{ ? = call functionName(<parameters>) }` or `{ ? = call procedureName(<parameters>}`. Native call syntax is not supported.

For Oracle the following rules apply:

- A function must return a result set. The first parameter of a procedure must be an `OUT` that returns a result set. This is done by using a `SYS_REFCURSOR` type in Oracle 9 or 10. In Oracle you need to define a `REF CURSOR` type. See Oracle literature for further information.

For Sybase or MS SQL server the following rules apply:

- The procedure must return a result set. Note that since these servers can 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.

- If you can enable `SET NOCOUNT ON` in your procedure it will probably be more efficient, but this is not a requirement.

## 18.3. Custom SQL for create, update and delete

Hibernate3 can use custom SQL for create, update, and delete operations. The SQL can be overridden at the statement level or inidividual column level. This section describes statement overrides. For columns, see Section 5.6, “Column transformers: read and write expressions”. Example 18.11, “Custom CRUD via annotations” shows how to define custom SQL operatons using annotations.

Example 18.11. Custom CRUD via annotations

    @Entity

    @Table(name="CHAOS")

    @SQLInsert( sql="INSERT INTO CHAOS(size, name, nickname, id) VALUES(?,upper(?),?,?)")

    @SQLUpdate( sql="UPDATE CHAOS SET size = ?, name = upper(?), nickname = ? WHERE id = ?")

    @SQLDelete( sql="DELETE CHAOS WHERE id = ?")

    @SQLDeleteAll( sql="DELETE CHAOS")

    @Loader(namedQuery = "chaos")

    @NamedNativeQuery(name="chaos", query="select id, size, name, lower( nickname ) as nickname from CHAOS where xml:id= ?", resultClass = Chaos.class)

    public class Chaos {

        @Id

        private Long id;

        private Long size;

        private String name;

        private String nickname;

`@SQLInsert`, `@SQLUpdate`, `@SQLDelete`, `@SQLDeleteAll` respectively override the INSERT, UPDATE, DELETE, and DELETE all statement. The same can be achieved using Hibernate mapping files and the `<sql-insert>`, `<sql-update>` and `<sql-delete>` nodes. This can be seen in Example 18.12, “Custom CRUD XML”.

Example 18.12. Custom CRUD XML

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

If you expect to call a store procedure, be sure to set the `callable` attribute to `true`. In annotations as well as in xml.

To check that the execution happens correctly, Hibernate allows you to define one of those three strategies:

- none: no check is performed: the store procedure is expected to fail upon issues

- count: use of rowcount to check that the update is successful

- param: like COUNT but using an output parameter rather that the standard mechanism

To define the result check style, use the `check` parameter which is again available in annoations as well as in xml.

You can use the exact same set of annotations respectively xml nodes to override the collection related statements -see Example 18.13, “Overriding SQL statements for collections using annotations”.

Example 18.13. Overriding SQL statements for collections using annotations

    @OneToMany

    @JoinColumn(name="chaos_fk")

    @SQLInsert( sql="UPDATE CASIMIR_PARTICULE SET chaos_fk = ? where id = ?")

    @SQLDelete( sql="UPDATE CASIMIR_PARTICULE SET chaos_fk = null where id = ?")

    private Set<CasimirParticle> particles = new HashSet<CasimirParticle>();

## Tip

The parameter order is important and is defined by the order Hibernate handles properties. You can see the expected order by enabling debug logging for the `org.hibernate.persister.entity` 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 through annotations or mapping files as that will override the Hibernate generated static sql)

Overriding SQL statements for secondary tables is also possible using `@org.hibernate.annotations.Table` and either (or all) attributes `sqlInsert`, `sqlUpdate`, `sqlDelete`:

Example 18.14. Overriding SQL statements for secondary tables

    @Entity

    @SecondaryTables({

        @SecondaryTable(name = "`Cat nbr1`"),

        @SecondaryTable(name = "Cat2"})

    @org.hibernate.annotations.Tables( {

        @Table(appliesTo = "Cat", comment = "My cat table" ),

        @Table(appliesTo = "Cat2", foreignKey = @ForeignKey(name="FK_CAT2_CAT"), fetch = FetchMode.SELECT,

            sqlInsert=@SQLInsert(sql="insert into Cat2(storyPart2, id) values(upper(?), ?)") )

    } )

    public class Cat implements Serializable {

The previous example also shows that you can give a comment to a given table (primary or secondary): This comment will be used for DDL generation.

## Tip

The SQL is directly executed in your database, so you can use any dialect you like. This will, however, reduce the portability of your mapping if you use database specific SQL.

Last but not least, stored procedures are in most cases required to return the number of rows inserted, updated and deleted. Hibernate always registers the first statement parameter as a numeric output parameter for the CUD operations:

Example 18.15. Stored procedures and their return value

    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;

## 18.4. Custom SQL for loading

You can also declare your own SQL (or HQL) queries for entity loading. As with inserts, updates, and deletes, this can be done at the individual column level as described in Section 5.6, “Column transformers: read and write expressions” or at the statement level. Here is an example of a statement level override:

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

This is just a named query declaration, as discussed earlier. You can reference this named query in a class mapping:

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

This even works with stored procedures.

You can even define a query for collection loading:

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

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

You can also define an entity loader that loads a collection by join fetching:

    <sql-query name="person">
        <return alias="pers" class="Person"/>
        <return-join alias="emp" property="pers.employments"/>
        SELECT NAME AS {pers.*}, {emp.*}
        FROM PERSON pers
        LEFT OUTER JOIN EMPLOYMENT emp
            ON pers.ID = emp.PERSON_ID
        WHERE xml:id=?
    </sql-query>

The annotation equivalent `<loader>` is the @Loader annotation as seen in Example 18.11, “Custom CRUD via annotations”.

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