[英]SQL Server Null or missing values in the stored procedure's parameters
我有以下存储过程:
CREATE PROCEDURE oc.add_discount (@course_id INT = '',
@level VARCHAR(100) = '',
@language VARCHAR(100) = '',
@series_name VARCHAR(100) = '',
@discount DECIMAL(5,4) = 0.0)
AS
BEGIN
SET @level = ISNULL(@level,'')
SET @language = ISNULL(@language,'')
SET @series_name = ISNULL(@series_name,'')
UPDATE oc.price
SET discount = @discount,
--discount based always on the original price
price = price/(1-discount)*(1-@discount)
WHERE
(@course_id NOT IN (SELECT course_id FROM oc.courses)
OR course_id IN (@course_id)) AND
(@level NOT IN (SELECT level FROM oc.level)
OR course_id IN (SELECT c.course_id
FROM oc.courses c
JOIN oc.level l ON c.level_id = l.level_id
WHERE l.level = LOWER(@level))) AND
(@language NOT IN (SELECT language FROM oc.language)
OR course_id IN (SELECT c.course_id
FROM oc.courses c
JOIN oc.language l ON c.language_id = l.language_id
WHERE l.language = UPPER(LEFT(@language,1))+LOWER(SUBSTRING(@language,2,LEN(@language))))) AND
(@series_name NOT IN (SELECT series_name FROM oc.series)
OR course_id IN (SELECT c.course_id
FROM oc.courses c
JOIN oc.series s ON c.series_id = s.series_id
WHERE s.series_name = @series_name))
IF @@ROWCOUNT<1
RAISERROR('Ooops something went wrong. No discount has been added. Avoid NULL or missing values, use '' instead!', 16, 0);
END;
我的问题是该过程在大多数情况下都可以正常工作,但是如果参数是 null 它不会更新任何内容,并且如果中间的参数丢失,我会收到错误消息。 我用一条错误消息解决了这个问题,但我想找到一个更优雅的解决方案。 有人可以帮我吗?
EXEC oc.add_discount 0.1, 1 ---- this query gives 10% discount for course ID 1
EXEC oc.add_discount 0.1, '', 'beginner', '', '' ---- this query 10% discount for every beginner course
EXEC oc.add_discount 0.1, NULL, 'beginner', '','' ---- "0 rows affected"
EXEC od.add_discount 0.1, ,'beginner', , ---- "Incorrect syntax near ','."
一般优先按名称调用参数:这样可以任意顺序调用参数。
EXEC oc.add_discount @course_id = 1, @level=''...
如果要使用有序参数调用过程:
您必须按顺序传递参数,并且可以跳过后续参数(前提是它们具有默认值)。
你不能跳过中间的参数。
提出您的问题,如果您想跳过中间参数并使用默认值调用它们,而不是硬编码它们。
EXEC oc.add_discount 0.1, DEFAULT, 'beginner', DEFAULT, DEFAULT
或者,如果你想传递 null 值,传递 null 值并在过程中处理它们
EXEC oc.add_discount 0.1, NULL, 'beginner', NULL, NULL
就您而言,您要处理两次。 我建议您按照以下方式进行。
CREATE PROCEDURE oc.add_discount (@course_id INT = NULL,
@level VARCHAR(100) = NULL,
@language VARCHAR(100) = NULL,
@series_name VARCHAR(100) = NULL,
@discount DECIMAL(5,4) = NULL)
as
SET @level = ISNULL(@level,'')
SET @language = ISNULL(@language,'')
SET @series_name = ISNULL(@series_name,'')
SET @discount = ISNULL(@discount ,0.0)
EXEC oc.add_discount 0.1
DEFAULT
参数调用EXEC oc.add_discount 0.1,DEFAULT,1,DEFAULT,DEFAULT,1
据我了解,您想在某些情况下跳过一些参数。 我建议您在执行存储过程时使用以下方法跳过参数。
EXEC od.add_discount @level='',@language='beginner'
但是,根据您的示例,我不建议对 INT 参数使用引号。 您应该考虑改用 NULL。
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