我有一个表SCHEDULES，其中包含LDATE列和SCHTYPEID列。如果SCHTYPEID = 1，则LDATE包含数字格式的日期（例如，今天及日期的20170918）。如果SCHTYPEID = 2，则LDATE包含0。
编写查询时，我会经常将LDATE转换为实际日期，并会过滤掉这样的零：
SELECT TO_DATE(LDATE, 'YYYYMMDD') LDATE
FROM SCHEDULES
WHERE SCHTYPEID = 1;
然而，当我把它放到视图中时
CREATE VIEW FOO (THE_DATE)
AS SELECT TO_DATE(LDATE, 'YYYYMMDD')
FROM SCHEDULES
WHERE SCHTYPEID = 1;
并对其进行查询：
SELECT *
FROM FOO
WHERE THE_DATE = TO_DATE(20170918, 'YYYYMMDD');
我收到错误＆＃34; ORA-01840：输入值不足以支持日期格式＆＃34;。像这样查询：
SELECT * FROM FOO;
工作得很好。但是，每当我尝试过滤它时，Oracle似乎忽略了视图中SCHTYPEID上的过滤器，它包含SCHTYPEID = 2的记录，导致错误。
我能做些什么来确保我只会查询填充了LDATE列的行吗？
答案 0 :(得分：2)
您可以让视图处理这两种情况（即使WHERE子句将数据限制为SCHTYPEID = 1），如下所示：
CREATE VIEW FOO(THE_DATE) AS
SELECT CASE WHEN SCHTYPEID = 1 THEN TO_DATE(LDATE, 'YYYYMMDD') ELSE NULL END
FROM SCHEDULES
WHERE SCHTYPEID = 1;
答案 1 :(得分：1)
CREATE VIEW FOO (THE_DATE)
AS SELECT TO_DATE(LDATE, 'YYYYMMDD')
FROM SCHEDULES
WHERE SCHTYPEID = 1
UNION ALL
SELECT TO_DATE('19000101', 'YYYYMMDD')
FROM SCHEDULES
WHERE SCHTYPEID = 2
答案 2 :(得分：0)
将日期纳入DATE列
并不会有什么坏处即使视图定义使用CASE语句来有条件地转换ldate列，sql语句也会导致错误。
DATE列中添加日期。这是最好的方法。假设您无法向表中添加约束，某些应用程序具有分配给各个字段的值集的功能（例如，Oracle Apps描述性弹性域属于此类别）。
假设您可能不希望/可以添加值集，您可以使用自定义实用程序包在事后检查数据。这将不太理想。
以下是我对这个问题的研究：
`SCOTT@dev>CREATE TABLE schedules
2 AS
3 ( SELECT
4 hiredate ldate,
5 to_number(TO_CHAR(hiredate,'YYYYMMDD') ) ldate_number,
6 1 schtypeid
7 FROM
8 emp
9 UNION ALL
10 SELECT
11 TO_DATE(NULL),
12 to_number(NULL),
13 2
14 FROM
15 dual
16 UNION ALL
17 SELECT
18 hiredate,
19 to_number(substr(
20 TO_CHAR(hiredate,'YYYYMMDD'),
21 1,
22 4
23 ) ),
24 1
25 FROM
26 emp
27 );
Table SCHEDULES created.
SCOTT@dev>SELECT
2 COUNT(1)
3 FROM
4 schedules;
COUNT(1)
29
创建一个实用程序包来检查/查看这些转换异常。我借用了许多人使用过的逻辑（见这些链接）：
Justin Cave的解决方案：How to handle to_date exceptions in a SELECT statment to ignore those rows?
Nicholas Krasnov的解决方案：What exact exception to be caugth while calling TO_DATE in pl/sql code
SCOTT@dev>CREATE OR REPLACE PACKAGE util AS
2 FUNCTION to_date_exception (
3 p_char_literal IN VARCHAR2,
4 p_date_format IN VARCHAR2
5 ) RETURN VARCHAR2;
6
7 FUNCTION my_to_date (
8 p_char_literal IN VARCHAR2,
9 p_date_format IN VARCHAR2
10 ) RETURN DATE;
11
12 END;
13 /
Package UTIL compiled
SCOTT@dev>CREATE OR REPLACE PACKAGE BODY util AS
2
3 FUNCTION to_date_exception (
4 p_char_literal IN VARCHAR2,
5 p_date_format IN VARCHAR2
6 ) RETURN VARCHAR2 IS
7 l_check_date DATE;
8 l_error_code VARCHAR(20);
9 l_error_message VARCHAR2(200);
10 BEGIN
11 l_check_date := TO_DATE(p_char_literal,p_date_format);
12 -- NULL will be returned when cast works
13 RETURN NULL;
14 EXCEPTION
15 WHEN OTHERS THEN
16 l_error_code := 'ORA' || TO_CHAR(sqlcode);
17 l_error_message := sqlerrm;
18 RETURN l_error_code;
19 END;
20
21 FUNCTION my_to_date (
22 p_char_literal IN VARCHAR2,
23 p_date_format IN VARCHAR2
24 ) RETURN DATE IS
25 l_date DATE;
26 BEGIN
27 l_date := TO_DATE(p_char_literal,p_date_format);
28 RETURN l_date;
29 EXCEPTION
30 WHEN OTHERS THEN
31 RETURN TO_DATE(NULL);
32 END;
33
34 END;
35 /
Package Body UTIL compiled
SCOTT@dev>SELECT
2 util.to_date_exception(ldate_number,'YYYYMMDD') excptn,
3 util.my_to_date(ldate_number,'YYYYMMDD') the_date_all,
4 ldate
5 FROM
6 schedules
7 WHERE
8 schtypeid = 1;
EXCPTN THE_DATE_ALL LDATE
17-DEC-1980 12:00:00 AM 17-DEC-1980 12:00:00 AM
20-FEB-1981 12:00:00 AM 20-FEB-1981 12:00:00 AM
22-FEB-1981 12:00:00 AM 22-FEB-1981 12:00:00 AM
02-APR-1981 12:00:00 AM 02-APR-1981 12:00:00 AM
28-SEP-1981 12:00:00 AM 28-SEP-1981 12:00:00 AM
01-MAY-1981 12:00:00 AM 01-MAY-1981 12:00:00 AM
09-JUN-1981 12:00:00 AM 09-JUN-1981 12:00:00 AM
09-DEC-1982 12:00:00 AM 09-DEC-1982 12:00:00 AM
17-NOV-1981 12:00:00 AM 17-NOV-1981 12:00:00 AM
08-SEP-1981 12:00:00 AM 08-SEP-1981 12:00:00 AM
12-JAN-1983 12:00:00 AM 12-JAN-1983 12:00:00 AM
03-DEC-1981 12:00:00 AM 03-DEC-1981 12:00:00 AM
03-DEC-1981 12:00:00 AM 03-DEC-1981 12:00:00 AM
23-JAN-1982 12:00:00 AM 23-JAN-1982 12:00:00 AM
ORA-1840 17-DEC-1980 12:00:00 AM
ORA-1840 20-FEB-1981 12:00:00 AM
ORA-1840 22-FEB-1981 12:00:00 AM
ORA-1840 02-APR-1981 12:00:00 AM
ORA-1840 28-SEP-1981 12:00:00 AM
ORA-1840 01-MAY-1981 12:00:00 AM
ORA-1840 09-JUN-1981 12:00:00 AM
ORA-1840 09-DEC-1982 12:00:00 AM
ORA-1840 17-NOV-1981 12:00:00 AM
ORA-1840 08-SEP-1981 12:00:00 AM
ORA-1840 12-JAN-1983 12:00:00 AM
ORA-1840 03-DEC-1981 12:00:00 AM
ORA-1840 03-DEC-1981 12:00:00 AM
ORA-1840 23-JAN-1982 12:00:00 AM
28 rows selected.
原始视图定义：
SCOTT@dev>CREATE OR REPLACE VIEW FOO
2 AS SELECT TO_DATE(ldate_number, 'FXYYYYMMDD') the_date,
3 ldate
4 FROM SCHEDULES
5 WHERE SCHTYPEID = 1;
View FOO created.
SCOTT@dev>SELECT
2 COUNT(1)
3 FROM
4 foo;
COUNT(1)
28
SCOTT@dev>SELECT
2 *
3 FROM
4 foo
5 WHERE
6 the_date = TO_DATE(20170918,'YYYYMMDD');
Error starting at line : 1 in command -
SELECT
*
FROM
foo
WHERE
the_date = TO_DATE(20170918,'YYYYMMDD')
Error report -
ORA-01840: input value not long enough for date format
**************************************
使用CASE语句建议的视图定义：
SCOTT@dev>CREATE OR REPLACE VIEW FOO(THE_DATE) AS
2 SELECT CASE WHEN SCHTYPEID = 1 THEN TO_DATE(ldate_number, 'YYYYMMDD') ELSE NULL END
3 FROM SCHEDULES
4 WHERE SCHTYPEID = 1;
View FOO created.
SCOTT@dev>SELECT
2 COUNT(1)
3 FROM
4 foo;
COUNT(1)
28
SCOTT@dev>list
1 SELECT
2 the_date
3 FROM
4 foo
5 WHERE
6* the_date = TO_DATE(20170918,'YYYYMMDD')
SCOTT@dev>/
Error starting at line : 1 in command -
SELECT
the_date
FROM
foo
WHERE
the_date = TO_DATE(20170918,'YYYYMMDD')
Error report -
ORA-01840: input value not long enough for date format
从这里可以看出（使用Oracle 12c），我认为CASE语句方法存在问题，并且应该通过确保错误数据不会进入此列来解决潜在问题。