JDBC更新计数行及调用存储过程返回多个结果集是本文我们主要要介绍的内容,在开始本文的时候,我们先了解SQL Server中的一个命令:SET NOCOUNT ON;执行该命令,表示不返回计数行,什么是计数行了,比如我们执行DELETE ,UPDATE,INSERT的时候,对多少条数据进行了修改,计数行的值就是多少?
SET NOCOUNT ON added to prevent extra result sets from interfering with SELECT statements.
在JDBC的操作数据库的过程中,你可以把Statement理解成为指向ResultSet的指针,假如数据库允许返回记数行的话,Statement将指向该计数行,比如
SET NOCOUNT ON; update TABLEA SET A='aa';--假设共100条数据被修改 SELECT * FROM TABLEA;
调用callableStatement.execute();后callableStatement指向受影响的计数行,当你再调用rs = callableStatement.getResultSet(); 的时候,结果集rs 为空。 无法查询出表TABLEA 的数据Statement提供了一个getMoreResults()的方法,该方法能将当前Statement "指针" 移动到下一个结果集。假如callableStatement.getUpdateCount()==-1&&getMoreResults()==true的话表明当前statement对象正指向一个真正的结果集。
For Examle:
package xx.qq.app; import java.sql.CallableStatement; import java.sql.Connection; import java.sql.ResultSet; import org.springframework.beans.factory.BeanFactory; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; import com.mchange.v2.c3p0.ComboPooledDataSource; /** * @author Jack Zhang Email:fish2-2@163.com * @date 2011-08-22 */ public class AppTest { public static void main(String[] args) throws Exception { ApplicationContext context = new ClassPathXmlApplicationContext( new String[] { "applicationContext.xml" }); BeanFactory factory = (BeanFactory) context; ComboPooledDataSource dataSource = (ComboPooledDataSource) factory .getBean("dataSource"); Connection con = dataSource.getConnection(); CallableStatement callableStatement = con .prepareCall("{call GetBasics( , )}"); callableStatement.setString(1, "w"); callableStatement.registerOutParameter(2, java.sql.Types.INTEGER); ResultSet rs=null; // 是否有结果集返回 boolean hasResultSet = callableStatement.execute(); // callableStatement--------->update System.out.println("执行存储过程后Statement是否指向真正的结果集:"+hasResultSet); System.out.println("受影响的行数:"+callableStatement.getUpdateCount()); callableStatement.getMoreResults();//------->select rs = callableStatement.getResultSet(); System.out.println("受影响的行:"+callableStatement.getUpdateCount()); while (rs.next()) { //System.out.println(rs.getObject(1)); } callableStatement.getMoreResults();//-------->update System.out.println("受影响的行:"+callableStatement.getUpdateCount()); callableStatement.getMoreResults();//-------->update System.out.println("受影响的行:"+callableStatement.getUpdateCount()); callableStatement.getMoreResults();//-------->select System.out.println("受影响的行:"+callableStatement.getUpdateCount()); rs = callableStatement.getResultSet();// 获取到真实的结果集 while (rs.next()) { //System.out.println(rs.getObject(1)); } callableStatement.getMoreResults();//--------->update System.out.println("受影响的行:"+callableStatement.getUpdateCount()); if (rs != null) rs.close(); if (callableStatement != null) callableStatement.close(); if (con != null) con.close(); } }
输出:
执行存储过程后是否返回结果集:false
受影响的行数:262 受影响的行:-1 ,此处返回结果集 受影响的行:262 受影响的行:262 受影响的行:-1,此处返回结果集 受影响的行:262存储过程
ALTER PROCEDURE GetBasics( @PERSON_NAME VARCHAR(32), @COUNT INT OUT ) AS BEGIN SET NOCOUNT ON; update TABLE_A SET NAME='aa'; SELECT @COUNTCOUNT = COUNT(*) FROM TABLE_A; update TABLE_A SET NAME='aa'; SELECT * FROM TABLE_A; update TABLE_A SET NAME='aa'; update TABLE_A SET NAME='aa'; SELECT * FROM ORGS; update TABLE_A SET NAME='aa'; END GO
以上就是JDBC更新计数行及调用存储过程返回多个结果集的过程的详细解释及实例说明,本文就介绍到这里了,希望本次的介绍能够对您有所收获!