在JAVA开发中通常碰到这样的需求,如果一条数据在表中已经存在,对其做update,如果不存在,将新的数据插入.
同时性能也不好,要来回数据库两次.
使用merge的话则可以一条SQL语句完成.
下面是JAVA代码的示例:(这里简单起见,没有对异常下连接关闭做处理)
private static void testMerge() throws SQLException {
// create table testtb(id int,val varchar2(10))
String sqlstr = "merge into testtb "
+ "using (select as newid, as newval from dual) newData "
+ "ON (testtb.id=newData.newid) "
+ "WHEN NOT MATCHED THEN "
+ "INSERT VALUES (newid,newval) "
+ "WHEN MATCHED THEN " + "UPDATE SET testtb.val=newData.newval";
Connection conn = NONXADBUtil.getConnection("jdbc:oracle:thin:@147.151.100.19:1521:orcl", "user", "pwd");
PreparedStatement sta = conn.prepareStatement(sqlstr);
sta.setInt(1, 1);
sta.setString(2, "new value");
sta.executeUpdate();
sta.close();
conn.commit();
conn.close();
}