您如何选择"HH24:MI:SSxFF6"格式的varchar2字段作为秒间隔(6)? [英] How do you select a varchar2 field in the format of 'HH24:MI:SSxFF6' as an INTERVAL HOUR TO SECOND(6)?

问题描述

以下查询成功:

SELECT INTERVAL '00:00:00.000000' HOUR TO SECOND(6)
FROM DUAL;

以下失败:

SELECT INTERVAL time_field HOUR TO SECOND(6) -- time_field is a VARCHAR2(15)
FROM some_table;

出现以下错误:

ORA-00923: FROM keyword not found where expected

如何解决第二个查询以将HOUR设置为秒间隔?

How do I fix my second query to pull back an HOUR TO SECOND INTERVAL?

当我尝试时:

SELECT cast(time_field AS INTERVAL HOUR TO SECOND(6))
FROM some_table

我得到以下信息:

ORA-00963: unsupported interval type

测试设置:

CREATE TABLE some_table (
   time_field VARCHAR2(50)
);

INSERT ALL
INTO some_table (time_field) VALUES ('10:00:00.000000')
INTO some_table (time_field) VALUES ('12:00:00.000000')
INTO some_table (time_field) VALUES ('15:00:00.000000')
INTO some_table (time_field) VALUES ('17:00:00.000000')
INTO some_table (time_field) VALUES ('20:00:00.000000')
INTO some_table (time_field) VALUES (NULL)
SELECT * FROM DUAL;

推荐答案

您可以使用 TO_DSINTERVAL函数;使用CTE复制表的示例:

You can use the TO_DSINTERVAL function; example here using a CTE to replicate your table:

WITH some_table AS (SELECT '00:00:00.000000' AS time_field FROM dual)
SELECT TO_DSINTERVAL('0 ' || time_field)
FROM some_table;

TO_DSINTERVAL('0'||TIME_FIELD)
---------------------------------------------------------------------------
+000000000 00:00:00.000000000

请注意，要使格式能够被函数识别，您必须提供天"部分，因此必须在虚拟'0 '字符串的前面.

Note that to make the format something the function recognises, you have to supply a 'days' part, hence the prepending of the dummy '0 ' string.

您的固定值查询返回的格式略有不同(或至少显示的格式略有不同；

Your fixed-value query returns a slightly different format (or at least displays slightly differently; interval daa types do not have format models in quite the same way as dates, so not sure how to express that accurately):

SELECT INTERVAL '00:00:00.000000' HOUR TO SECOND(6)
FROM DUAL;

INTERVAL'00:00:00.000000'HOURTOSECOND(6)
---------------------------------------------------------------------------
+00 00:00:00.000000

要进行复制，可以在需要时进行cast

To replicate that you can cast this if you need to:

WITH some_table AS (SELECT '00:00:00.000000' AS time_field FROM dual)
SELECT CAST(TO_DSINTERVAL('0 ' || time_field) AS INTERVAL DAY TO SECOND(6))
FROM some_table;

CAST(TO_DSINTERVAL('0'||TIME_FIELD)ASINTERVALDAYTOSECOND(6))
---------------------------------------------------------------------------
+00 00:00:00.000000

...或者仅仅是:

WITH some_table AS (SELECT '00:00:00.000000' AS time_field FROM dual)
SELECT CAST('0 ' || time_field AS INTERVAL DAY TO SECOND(6))
FROM some_table;

CAST('0'||TIME_FIELDASINTERVALDAYTOSECOND(6))
---------------------------------------------------------------------------
+00 00:00:00.000000

...这几乎是@catcall最初建议的，但这也需要在前面加上'0 '，否则您将得到一个ORA-01867. (或者，如果您尝试使用HOUR TO SECOND，ORA-00963，即使使用预设的日期值).但是，我猜(虽然只是受过很小的教育，但这只是一个猜测)，它正在执行隐式TO_DSINTERVAL或类似操作，并且我认为我更喜欢使用一个显式的TO_DSINTERVAL，因此可以肯定发生了什么.不过那可能只是我...

... which is pretty much what @catcall first suggested, but this also needs the '0 ' prepended, or you get an ORA-01867. (Or, if you try to use HOUR TO SECOND, ORA-00963, even with the prepended day value). However, I guess (and it is just a guess, though very slightly educated) that it's doing an implicit TO_DSINTERVAL or similar, and I think I'd prefer to use an explicit one so I was sure what's happening. That might just be me, though...

使用样本数据我也得到一个ORA-01867，但这是由空值引起的.您可以使用case在结果中将其保留为空:

Using your sample data I too get an ORA-01867, but it's caused by the null value. You can use a case to leave that as null in the result:

SELECT CASE WHEN time_field IS NULL THEN null
    ELSE CAST('0 ' || time_field AS INTERVAL DAY TO SECOND(6)) END
FROM some_table;

CASEWHENTIME_FIELDISNULLTHENNULLELSECAST('0'||TIME_FIELDASINTERVALDAYTOSECO
---------------------------------------------------------------------------
+00 10:00:00.000000
+00 12:00:00.000000
+00 15:00:00.000000
+00 17:00:00.000000
+00 20:00:00.000000


6 rows selected.

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