Hibernate created a new language named Hibernate Query Language (HQL), the syntax is quite similar to database SQL language. The main difference between the two is that HQL uses class name instead of table name, and property names instead of column name.

HQL is extremely simple to learn and use, and the code is always self-explanatory.

1. HQL Select Query Example

Retrieve a stock data where stock code is “7277″.

Query query = session.createQuery("from Stock where stockCode = :code ");
query.setParameter("code", "7277");
List list = query.list();
Query query = session.createQuery("from Stock where stockCode = '7277' ");
List list = query.list();

2. HQL Update Query Example

Update a stock name to “DIALOG1″ where stock code is “7277″.

Query query = session.createQuery("update Stock set stockName = :stockName" +
    				" where stockCode = :stockCode");
query.setParameter("stockName", "DIALOG1");
query.setParameter("stockCode", "7277");
int result = query.executeUpdate();
Query query = session.createQuery("update Stock set stockName = 'DIALOG2'" +
    				" where stockCode = '7277'");
int result = query.executeUpdate();

3. HQL Delete Query Example

Delete a stock where stock code is “7277″.

Query query = session.createQuery("delete Stock where stockCode = :stockCode");
query.setParameter("stockCode", "7277");
int result = query.executeUpdate();
Query query = session.createQuery("delete Stock where stockCode = '7277'");
int result = query.executeUpdate();

4. HQL Insert Query Example

In HQL, only the INSERT INTO … SELECT … is supported; there is no INSERT INTO … VALUES. HQL only support insert from another table. For example

"insert into Object (id, name) select oo.id, oo.name from OtherObject oo";

Insert a stock record from another backup_stock table. This can also called bulk-insert statement.

Query query = session.createQuery("insert into Stock(stock_code, stock_name)" +
    			"select stock_code, stock_name from backup_stock");
int result = query.executeUpdate();

The query.executeUpdate() will return how many number of record has been inserted, updated or deleted.

Reference

1. http://docs.jboss.org/hibernate/core/3.3/reference/en/html/queryhql.htm

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