这里有两个sql。他们大体相同。但执行效率却是天壤之别。一个1秒就可以查询出结果，而一个需要10多分钟。查看他们的执行计划，发现果然不通。
sql1：
SQL code:
SELECT distinct t.CARD_ID AS CARD_ID,
t.ZONECODE AS ZONECODE,
t.flag as FLAG,
(select zonename from zonecode where zonecode = t.zonecode) as zonename,
(select orgname
from aidszh_sgra_organise
where orgcode = t.orgcode) as orgname,
t.PID_ORG AS PID_ORG,
t.ORGCODE AS ORGCODE,
t.CARD_CODE AS CARD_CODE,
t.EMPID_CREATE_ORG as EMPID_CREATE_ORG,
t.PID AS PID,
t.ANTIN AS ANTIN,
t.PATIENT_NAME AS PATIENT_NAME,
t.ID AS ID,
(select name from aidszh_sgra_dd_sex where id = t.SEX) AS SEX,
to_char(t.BIRTHDAY, 'yyyy-mm-dd') AS BIRTHDAY,
(select name
from aidszh_sgra_dd_chargesrc
where id_dic = t.CHARGESRC) AS CHARGESRC,
to_char(t.DT_ANTIVIRUS, 'yyyy-mm-dd') AS DT_ANTIVIRUS,
(select name from aidszh_sgra_dd_flag where id = t.FLAG) AS FLAGSTATUS,
to_char(t.DT_REPORT, 'yyyy-mm-dd') AS DT_REPORT,
to_char(t.TM
private static final String URL = "jdbc:oracle:thin:@localhost:1521:orcl";
private static final String USERNAME = "sys";
private static final String PASSWORD = "s ......
