Jdbc執行很慢，而PLSQL執行快的問題解決

最近在檢查一方法時發現程序執行SQL查詢時非常慢，但使用PLSQL DEV工具執行查詢語句又很快。

看以下代碼：

public boolean isExistSonoByStoreCode(String storeCode, String soNo, String billId)
    {
    	StringBuffer sql = new StringBuffer();
    	sql.append("select bill_id, so_no from store_in_head where store_code = ? and UPPER(so_no) = UPPER(?) ");
    	
        DBUtil dbu = null;
        PreparedStatement preStmt = null;
        ResultSet rs = null;
        boolean isExistSono = false;
        
        try 
        {
            dbu = new DBUtil();
            preStmt = dbu.getConnection().prepareStatement(sql.toString());
            preStmt.setString(1, storeCode);
            preStmt.setString(2, soNo);
            rs = preStmt.executeQuery();
            while (rs.next()) 
            {
            	String oldBillId = rs.getString("bill_id");
            	
            	if (!oldBillId.equalsIgnoreCase(billId))
            	{
            		isExistSono = true;
            	}
            }
        }
        catch (Exception e) 
        {
            log.error(e.getMessage(),e);
        }
        finally 
        {
            try 
            {
                rs.close();
            }
            catch (Exception e) 
            {
            	;
            }
            
            try 
            {
                preStmt.close();
            }
            catch (Exception e) 
            {
            	;
            }
            closeDButil(dbu);
        }
       
    	return isExistSono;
    }

 經DEBUG發現速度慢確實發生在查詢時，即執行rs = preStmt.executeQuery();時

一開始懷疑是語句使用UPER函數導致的，但是把語句修改爲不使用函數也一樣慢。。懷疑是使用了PreparedStatement 參數需要動態綁定問題，於是將PreparedStatement 改爲Statement ，執行卻很快，修改後的代碼如下：

 public boolean isExistSonoByStoreCode(String storeCode, String soNo, String billId)
    {
    	StringBuffer sql = new StringBuffer();
    	sql.append("select bill_id, so_no from store_in_head where store_code = '" + storeCode + "' and UPPER(so_no) = UPPER('"+ soNo +"') ");
    	
        DBUtil dbu = null;
        Statement preStmt = null;
        ResultSet rs = null;
        boolean isExistSono = false;
        
        try 
        {
            dbu = new DBUtil();
            preStmt = dbu.getConnection().createStatement();
            rs = preStmt.executeQuery(sql.toString());
//            preStmt.setString(1, storeCode);
//            preStmt.setString(2, soNo);
//            rs = preStmt.executeQuery();
            while (rs.next()) 
            {
            	String oldBillId = rs.getString("bill_id");
            	
            	if (!oldBillId.equalsIgnoreCase(billId))
            	{
            		isExistSono = true;
            	}
            }
        }
        catch (Exception e) 
        {
            log.error(e.getMessage(),e);
        }
        finally 
        {
            try 
            {
                rs.close();
            }
            catch (Exception e) 
            {
            	;
            }
            
            try 
            {
                preStmt.close();
            }
            catch (Exception e) 
            {
            	;
            }
            closeDButil(dbu);
        }
       
    	return isExistSono;
    }

 字段類型：STORE_CODE CHAR(3)，SO_NO VARCHAR2(100)

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