????5??????????????????

????-->?????????business_date??????????????????????????

????-->??Ч??

SELECT *
FROM   acc_pos_int_tbl
WHERE  business_date = 20090201??

Execution Plan
----------------------------------------------------------
Plan hash value: 2335235465

-------------------------------------------------------------------------------------
| Id  | Operation         | Name            | Rows  | Bytes | Cost (%CPU)| Time     |
-------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT  |                 | 37516 |  2857K|   106K  (1)| 00:21:17 |
|*  1 |  TABLE ACCESS FULL| ACC_POS_INT_TBL | 37516 |  2857K|   106K  (1)| 00:21:17 |
-------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------
     1 - filter(TO_NUMBER("BUSINESS_DATE")=20090201)    -->???????????????????????

????-->??Ч??

SELECT *
FROM   acc_pos_int_tbl
WHERE  business_date = '20090201'

????6????????????? NULL ?

????IS NULL??IS NOT NULL?????????????????????????????????NULL?????????NULL????????NULL?.??NULL????洢??????????У???????????????????????????NULL?

SELECT acc_num
     ?? pl_cd
     ?? order_qty
     ?? trade_date
FROM   trade_client_tbl
WHERE  input_date IS NOT NULL;

Execution Plan
----------------------------------------------------------
Plan hash value: 901462645
--------------------------------------------------------------------------------------
| Id  | Operation         | Name             | Rows  | Bytes | Cost (%CPU)| Time     |
--------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT  |                  |     1 |    44 |    15   (0)| 00:00:01 |
|*  1 |  TABLE ACCESS FULL| TRADE_CLIENT_TBL |     1 |    44 |    15   (0)| 00:00:01 |
--------------------------------------------------------------------------------------

alter table trade_client_tbl modify (input_date not null);

??????????????????

SELECT * FROM table_name WHERE col IS NOT NULL
SELECT * FROM table_name WHERE col IS NULL

?????????????

SELECT * FROM table_name WHERE col >= 0 --?????????? =?? >=?? <=?? like ???????

???????????

????1????????С??????????????м????????????????????????????????????????????

????2???where????е?ν?????????????·????rowid??????????????

????3????ú????SQLд????????????Oracle????????????????

????4????????????????????????????????????Ч??????????????????????????????????hash??????