sql - 在 Oracle 中处理异常
问题描述
我正在尝试将输入的年份解析为字符串(请不要让我开始 - 它就是这样)。然而,有些年份无法解析TO_NUMBER
。
WITH src AS (
SELECT '2000' AS y FROM DUAL
UNION SELECT '1991' AS y FROM DUAL
UNION SELECT '20--' AS y FROM DUAL
UNION SELECT '09' AS y FROM DUAL
UNION SELECT '11' AS y FROM DUAL
UNION SELECT '95' AS y FROM DUAL
)
BEGIN
SELECT
s.y,
TO_NUMBER(s.y) AS p
FROM src s
EXCEPTION
WHEN INVALID_NUMBER THEN NULL
END
我从来没有在 Oracle 中进行过异常处理,所以如果这是一个如此基本的问题,我深表歉意。
在上面运行我的查询时,我得到ORA-00928: missing SELECT keyword
然后它突出显示BEGIN
关键字。通过搜索,我看到人们所做的就是使用BEGIN SELECT
,这也是我正在做的事情。我猜我在其他地方搞砸了?
基本上我想要做的是解析字符串,如果抛出异常,我只需将其设置为NULL
.
编辑
我尝试了一种不同的方法并添加了一些分号,正如@DavidFaber 在下面评论的那样。
BEGIN
SELECT
s.y,
TO_NUMBER(s.y) AS p
FROM (
SELECT '2000' AS y FROM DUAL
UNION SELECT '1991' AS y FROM DUAL
UNION SELECT '20--' AS y FROM DUAL
UNION SELECT '09' AS y FROM DUAL
UNION SELECT '11' AS y FROM DUAL
UNION SELECT '95' AS y FROM DUAL
) s;
EXCEPTION
WHEN INVALID_NUMBER THEN NULL;
END;
我现在得到一个不同的错误ORA-06550: line 2, column 3: PLS-00428: an INTO clause is expected in this SELECT statement
。
解决方案
是的,这是真的,但是有像内联函数(Oracle 12c)这样的解决方法:
WITH FUNCTION safe_to_NUMBER(input IN VARCHAR2)
RETURN NUMBER IS
i NUMBER;
BEGIN
i:= TO_NUMBER(input);
RETURN i;
EXCEPTION
WHEN OTHERS THEN
RETURN NULL;
END;
SELECT sub.y, safe_to_NUMBER(sub.y)
FROM (
SELECT '2000' AS y FROM DUAL UNION ALL
SELECT '1991' AS y FROM DUAL UNION ALL
SELECT '20--' AS y FROM DUAL UNION ALL
SELECT '09' AS y FROM DUAL UNION ALL
SELECT '11' AS y FROM DUAL UNION ALL
SELECT '95' AS y FROM DUAL
) sub;
结果:
Y SAFE_TO_NUMBER(SUB.Y)
---- ---------------------
2000 2000
1991 1991
20--
09 9
11 11
95 95
6 rows selected.
当然我不会写这样的生产代码:)
正确的方法(DEFAULT NULL ON CONVERSION ERROR
- 从 Oracle12cR2 开始可用):
SELECT sub.y, TO_NUMBER(sub.y DEFAULT NULL ON CONVERSION ERROR) AS y
FROM (
SELECT '2000' AS y FROM DUAL UNION ALL
SELECT '1991' AS y FROM DUAL UNION ALL
SELECT '20--' AS y FROM DUAL UNION ALL
SELECT '09' AS y FROM DUAL UNION ALL
SELECT '11' AS y FROM DUAL UNION ALL
SELECT '95' AS y FROM DUAL
) sub;
输出:
Y Y
---- ----------
2000 2000
1991 1991
20--
09 9
11 11
95 95
6 rows selected.