Oracle分页

自己的练习:

/*****普通的查询(30数据)****/
select * from ENVIRONMENT_APPLY_AUDIT;


/*******查询带行号的数据**/
select ROWNUM ru,AAA.* from (      select * from ENVIRONMENT_APPLY_AUDIT   ) AAA;

/*******查询第一页   每页5条数据***/
select * from (select AAA.*,ROWNUM ru from (select * from ENVIRONMENT_APPLY_AUDIT ) AAA where ROWNUM<6);
select * from (select ROWNUM ru,AAA.* from (select * from ENVIRONMENT_APPLY_AUDIT ) AAA where ROWNUM<6) where ru>0;


/**********查询第二页数据********************/
select * from (select ROWNUM ru,AAA.* from (select * from ENVIRONMENT_APPLY_AUDIT ) AAA where ROWNUM<11) where ru>5;


/**********查询第三页数据********************/
select * from (select ROWNUM ru,AAA.* from (select * from ENVIRONMENT_APPLY_AUDIT ) AAA where ROWNUM<16) where ru>10;

 查询分页就是在原来语句的查询条件上加上根据行号分页的条件，注意与mysql不同的是oracle是从1开始。假设页大小都是5:

mysql分页计算:

页号	起始索引	取几个
1	0	5
2	5	5

　　计算第一页:limit 0,5

　　　　　第二页: limit 5,5

 　　　 　规律: limit (pageNum-1)*pageSize,pageSize

Oracle计算分页:

页号	起始行号	最大行号
1	1	5
2	6	10

　　　　　　

 　　计算第一页:ROWNUM<=5) where ru>0; 

 　　　　第二页:ROWNUM<=10) where ru>5;

　　　　规律:ROWNUM<=pageSize*pageNum)where ru>(pageNum-1)*pageSize;

 mybatis利用oracle进行分页就是在上面原始语句的基础上包装两层之后进行分页查询:

例如一个原生的java分页Oracle:

package daoImpl;

import java.math.BigDecimal;
import java.sql.SQLException;
import java.util.List;

import javax.sql.DataSource;

import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import org.apache.commons.dbutils.handlers.ScalarHandler;
import org.junit.Test;

import bean.Emp;
import dao.Empdao;
import utils.DataSourceUtils;
/**
 * 员工管理模块
* @author: qlq
* @date :  2017年7月14日上午9:59:51
* @description:Empdao的实现类
 */

public class EmpDaoImpl implements Empdao {

    /**
     * 获取总的记录数
     */
    @SuppressWarnings("unchecked")
    @Override
    public int findAllRecord() throws Exception {
        QueryRunner qr = new QueryRunner(DataSourceUtils.getDataSource());
        String sql = "SELECT COUNT(ID) FROM EMP";
        @SuppressWarnings({ "unused", "rawtypes" })
        BigDecimal bg  = qr.query(sql, new ScalarHandler());
        return bg.intValue();
    }

    /**
     * 获取分页记录
     */
    @Override
    public List<Emp> findAllRecord(int start, int end) throws Exception {
        QueryRunner qr = new QueryRunner(DataSourceUtils.getDataSource());
        String sql = " select xx.id,xx.name,xx.hiredate "+
        " from (select rownum xid,emp.* from emp where rownum<?) xx where  xid>?";        
        Object[]  paras={end,start};
        return qr.query(sql, new BeanListHandler<Emp>(Emp.class), paras);
    }
    @Test
    public void test1() throws SQLException{
        EmpDaoImpl eDaoImpl = new EmpDaoImpl();
        try {
            System.out.println("共有"+eDaoImpl.findAllRecord()+"条记录");
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        System.out.println("取第2页数据------------------");
        try {
            System.out.println(eDaoImpl.findAllRecord(5, 11));
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

}

　　 ibatis进行分页的通用(isParameterPresent标签是通用的，可以放在任何需要进行分页查询的sql中)查询:(每次分页都是传一个pagination参数为true(传入起始和结束为止)，然后在原来的查询条件上进行两次包装即可完成分页)

  <select id="ibatorgenerated_selectByExample" resultMap="ibatorgenerated_BaseResultMap" parameterClass="com.tyust.bean.en.EnApplyInfoExample" >
    <!--
      WARNING - This element is automatically generated by Apache iBATIS ibator, do not modify.
    -->
        <isParameterPresent>
        <isEqual property="pagination" compareValue="true">
           <![CDATA[SELECT * FROM
            (
            SELECT A.*, ROWNUM RN
            FROM (
           ]]>
        </isEqual>
    </isParameterPresent>
    select ENVIRONMENT_APPLY_ID, ENVIRONMENT_APPLY_UNIT_ID, ENVIRONMENT_APPLY_USER_ID,
      ENVIRONMENT_APPLY_TEL, ENVIRONMENT_APPLY_STATUS, ENVIRONMENT_APPLY_DATE,
      ENVIRONMENT_APPLY_OPINION, ENVIRONMENT_APPLY_SAMPLY, ENVIRONMENT_APPLY_PRODUCTION,
      ENVIRONMENT_APPLY_USER_NAME
    from ENVIRONMENT_APPLY_INFO
    <isParameterPresent >
      <include refid="ENVIRONMENT_APPLY_INFO.ibatorgenerated_Example_Where_Clause" />
      <isNotNull property="orderByClause" >
        order by $orderByClause$
      </isNotNull>
    </isParameterPresent>
     <isParameterPresent>
        <isEqual property="pagination" compareValue="true">
            <![CDATA[
                ) A
                WHERE ROWNUM <=#limit#
                )
                WHERE RN >#start#
            ]]>
        </isEqual>
    </isParameterPresent>
  </select>