JDBC - 查询执行

Question

Can someone help me executing the following SQL in java using JDBC?

 MERGE INTO ent_emp_policy e 
 USING(select e.ENTEMPPOL_ID,e.emp_id,e.entemppol_start_date,e.ENTEMPPOL_END_DATE, nvl(lead(e.entemppol_start_date,1) over (partition by e.emp_id order by e.emp_id,e.entemppol_start_date)-1,e.ENTEMPPOL_END_DATE) as correct_end_dt from ent_emp_policy e ,(select e1.emp_id from ent_emp_policy e1 where e1.ENTEMPPOL_END_DATE='01-jan-3000' group by e1.emp_id having count(*)>1) P where e.ENTEMPPOL_END_DATE='01-jan-3000'and e.emp_id=p.emp_id )ef ON(e.ENTEMPPOL_ID=ef.ENTEMPPOL_ID)WHEN MATCHED THEN UPDATE SET e.ENTEMPPOL_END_DATE = ef.correct_end_dt; 

The SQL is doing the following steps:

1. Retrieves all emp_ids having more than 1 '01-Jan-3000' end dates;

2. Uses oracle window function to retrieve start date for next row in partition for particular emp id subtracts 1 day from next start date to correct end date.

3. Updates ent_emp_policy using Merge to correct ENT EMPPOL_END_DATE for that particular ENTEMPPOL_ID.

    private void processDupEndDate(long empID, java.util.Date start, DBConnection conn) throws SQLException{ PreparedStatement ps = null; ResultSet rs = null; int result = 0; try { StringBuffer sb = new StringBuffer(); sb.append("MERGE INTO ent_emp_policy e USING ") .append(("select e.ENTEMPPOL_ID,e.emp_id,e.entemppol_start_date,e.ENTEMPPOL_END_DATE, nvl(lead (e.entemppol_start_date,1) over (partition by e.emp_id order by e.emp_id,e.entemppol_start_date)-1,e.ENTEMPPOL_END_DATE) as correct_end_dt") .append(" from ent_emp_policy e , ") .append((" select e1.emp_id from ent_emp_policy e1 ") .append(" where e1.ENTEMPPOL_END_DATE='01-JAN-3000' group by e1.emp_id having count(*)>1) P ") .append(" where e.ENTEMPPOL_END_DATE='01-JAN-3000' ") .append(" and e.emp_id=p.emp_id") .append(" ) ef ") .append(" ON(e.ENTEMPPOL_ID=ef.ENTEMPPOL_ID) ") .append(" WHEN MATCHED THEN UPDATE SET ") .append(" e.ENTEMPPOL_END_DATE = ef.correct_end_dt); "); ps = conn.prepareStatement(sb.toString()); ps.setTimestamp(1,new java.sql.Timestamp(DateHelper.addDays(start,-1).getTime())); ps.setLong(2,empId); ps.setTimestamp(3,new java.sql.Timestamp(start.getTime())); ps.setTimestamp(4,new java.sql.Timestamp(start.getTime())); ps.setLong(5,empId); ps.setTimestamp(6,new java.sql.Timestamp(DateHelper.addDays(start,-1).getTime())); rs = ps.executeQuery(); conn.commit(); } catch (SQLException e) { conn.rollback(); } finally { if (rs != null) rs.close(); if (ps != null) ps.close(); } }

Answer 1

Basic steps are described in the JDBC Getting started guide

You need to:

• Open a connection to your database
• Create a statement object
• Execute the query (using executeUpdate method)
• Commit changes
• Close the statement and the connection

Sample code (copied from the documentation and slightly modified):

public static void main (String args []) throws SQLException
{

    String sql = "MERGE INTO ent_emp_policy e "
      + " USING(select  e.ENTEMPPOL_ID,e.emp_id,e.entemppol_start_date,e.ENTEMPPOL_END_DATE,"
      + " nvl(lead(e.entemppol_start_date,1) over (partition by e.emp_id order by e.emp_id,e.entemppol_start_date)-1,e.ENTEMPPOL_END_DATE) as "
      + " correct_end_dt from ent_emp_policy e ,(select e1.emp_id from ent_emp_policy e1 where e1.ENTEMPPOL_END_DATE='01-jan-3000' group by e1.emp_id having count(*)>1) P "
      + " where e.ENTEMPPOL_END_DATE='01-jan-3000'and e.emp_id=p.emp_id )ef ON(e.ENTEMPPOL_ID=ef.ENTEMPPOL_ID)WHEN MATCHED THEN UPDATE SET e.ENTEMPPOL_END_DATE = ef.correct_end_dt";


    OracleDataSource ods = null;
    Connection conn = null;
    Statement stmt = null;

    // Create DataSource and connect to the local database
    ods = new OracleDataSource();
    ods.setURL("jdbc:oracle:thin:@//myhost:1521/orcl");
    ods.setUser("scott");
    ods.setPassword("tiger");
    conn = ods.getConnection();

    try {
        // Execute the query
        stmt = conn.createStatement (); 
        stmt.executeUpdate (sql);

        // commit changes
        conn.commit();
    } finally {
      if(stmt!=null) stmt.close();
      if(conn!=null) conn.close();
    }
}