日期比较返回异常结果 - SQL Oracle [英] Date comparison returns unusual result - SQL Oracle
问题描述
我有一张结构表:
+---------+--------------+-----------------+---------------+-------+------+
| week_no | long_week_no | week_start_date | week_end_date | month | year |
+---------+--------------+-----------------+---------------+-------+------+
| 1 | 1A | 01/01/2015 | 03/01/2015 | JAN | 2015 |
| 1 | 1B | 04/01/2015 | 10/01/2015 | JAN | 2015 |
| 2 | 2 | 11/01/2015 | 17/01/2015 | JAN | 2015 |
| 3 | 3 | 18/01/2015 | 24/01/2015 | JAN | 2015 |
| .. | .. | .. | .. | .. | .. |
| 51 | 51 | 14/12/2014 | 20/12/2015 | DEC | 2014 |
+---------+--------------+-----------------+---------------+-------+------+当我运行以下语句时:
SELECT *
FROM loy_period
WHERE To_date('15/04/2015', 'DD/MM/YYYY') BETWEEN
To_date(week_start_date, 'DD/MM/YYYY') AND
To_date(week_end_date, 'DD/MM/YYYY');
和
SELECT *
FROM loy_period
WHERE To_date('15/04/2015', 'DD/MM/YYYY') BETWEEN
week_start_date AND
week_end_date;
它返回以下内容:
+---------+--------------+-----------------+---------------+-------+------+
| week_no | long_week_no | week_start_date | week_end_date | month | year |
+---------+--------------+-----------------+---------------+-------+------+
| 51 | 51 | 14/12/2014 | 20/12/2015 | DEC | 2014 |
| 1 | 1A | 01/01/2015 | 03/01/2015 | JAN | 2015 |
+---------+--------------+-----------------+---------------+-------+------+当我使用任何日期运行它时，它会返回正确的时间段以及week_no 51 记录！
And when I run it with any date, it will return the correct period in addition to the week_no 51 record!
我很困惑为什么会发生这种情况.week_start_date 和 week_end_date 列都属于 date 类型.
I'm confused why this is happening. Both columns week_start_date and week_end_date of the type date.
Fiddle 按预期工作.
推荐答案
它非常适合我正确使用TO_DATE和DATE值.
It works perfectly for me with proper use of TO_DATE and DATE values.
切勿在 DATE 上使用 TO_DATE，它会将其隐式转换为字符串，然后使用特定于语言环境的 NLS 格式返回日期em>.
Never use TO_DATE on a DATE, It will implicitly convert it into string and then back to date using locale-specific NLS format.
'01/01/2015' 不是日期，而是字符串.您必须使用 TO_DATE 将其显式转换为 DATE.
'01/01/2015' is NOT a DATE, it is a STRING. You must use TO_DATE to explicitly convert it into DATE.
看看会发生什么:
SQL> explain plan for select * from dual where to_date(sysdate) > to_date(sysdate -1);
Explained.
SQL> select * from table(dbms_xplan.display);
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
Plan hash value: 3752461848
---------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 2 | 2 (0)| 00:00:01 |
|* 1 | FILTER | | | | | |
| 2 | TABLE ACCESS FULL| DUAL | 1 | 2 | 2 (0)| 00:00:01 |
---------------------------------------------------------------------------
Predicate Information (identified by operation id):
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
---------------------------------------------------
1 - filter(TO_DATE(TO_CHAR(SYSDATE@!))>TO_DATE(TO_CHAR(SYSDATE@!-1)))
14 rows selected.
SQL>
因此，实际应用的过滤器是 filter(TO_DATE(TO_CHAR(SYSDATE@!)) 由于基于特定于区域设置的 NLS 格式的隐式转换，您将得到不正确的输出.
So, the actual filter applied is filter(TO_DATE(TO_CHAR(SYSDATE@!)) You will get incorrect output due to the implicit conversion based on locale-specific NLS format.
无论如何，现在回到你最初的问题.
Anyway, now coming back to your original question.
例如
假设您的数据如下所示:
Let's say your data looks like:
设置:
SQL> CREATE TABLE t
2 (week_no VARCHAR2(2), long_week_no VARCHAR2(2), week_start_date DATE, week_end_date DATE, mnth VARCHAR2(3), yr VARCHAR2(4))
3 ;
Table created.
SQL>
SQL>
SQL> INSERT ALL
2 INTO t (week_no, long_week_no, week_start_date, week_end_date, mnth, yr)
3 VALUES ('1', '1A', TO_DATE('01/01/2015','DD/MM/YYYY'), TO_DATE('03/01/2015','DD/MM/YYYY'), 'JAN', '2015')
4 INTO t (week_no, long_week_no, week_start_date, week_end_date, mnth, yr)
5 VALUES ('1', '1B', TO_DATE('04/01/2015','DD/MM/YYYY'), TO_DATE('10/01/2015','DD/MM/YYYY'), 'JAN', '2015')
6 INTO t (week_no, long_week_no, week_start_date, week_end_date, mnth, yr)
7 VALUES ('2', '2', TO_DATE('11/01/2015','DD/MM/YYYY'), TO_DATE('17/01/2015','DD/MM/YYYY'), 'JAN', '2015')
8 INTO t (week_no, long_week_no, week_start_date, week_end_date, mnth, yr)
9 VALUES ('3', '3', TO_DATE('18/01/2015','DD/MM/YYYY'), TO_DATE('24/01/2015','DD/MM/YYYY'), 'JAN', '2015')
10 INTO t (week_no, long_week_no, week_start_date, week_end_date, mnth, yr)
11 VALUES ('51', '51', TO_DATE('20/12/2014','DD/MM/YYYY'), TO_DATE('26/12/2015','DD/MM/YYYY'), 'DEC', '2014')
12 SELECT * FROM dual
13 ;
5 rows created.
SQL>
SQL> COMMIT;
Commit complete.
SQL>
表格:
SQL> SELECT * FROM t;
WE LO WEEK_STAR WEEK_END_ MNT YR
-- -- --------- --------- --- ----
1 1A 01-JAN-15 03-JAN-15 JAN 2015
1 1B 04-JAN-15 10-JAN-15 JAN 2015
2 2 11-JAN-15 17-JAN-15 JAN 2015
3 3 18-JAN-15 24-JAN-15 JAN 2015
51 51 20-DEC-14 26-DEC-15 DEC 2014
SQL>
查询以根据 DATE 范围过滤行:
SQL> SELECT *
2 FROM t
3 WHERE To_date('15/01/2015', 'DD/MM/YYYY') BETWEEN
4 week_start_date AND
5 week_end_date;
WE LO WEEK_STAR WEEK_END_ MNT YR
-- -- --------- --------- --- ----
2 2 11-JAN-15 17-JAN-15 JAN 2015
51 51 20-DEC-14 26-DEC-15 DEC 2014
SQL>
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