Question

我正在编写程序，我希望使用从日期到日期的小日期时间来过滤日期。从某个时候起，日期可以为null，而在比较时，To Date也可以为null 当日期或日期可以为空时，过滤日期。

我尝试过以下查询，但它给了我错误。

 SELECT RQ.int_REPS_QUES_DIFF_LEVEL,SUM(1) AS NoOFDificultyQuestion FROM   
 REPS_TEST_QUES_ASSIGNED RQA   
 INNER JOIN REPS_QUESTION RQ ON RQA.int_REPS_TEST_QUES_ASSG_QUESID=RQ.PK_REPS_QUES_ID  
 WHERE int_REPS_TEST_ID IN(  
 SELECT FK_TEST_ID FROM STUDENT_EXAM SE WHERE FK_USER_ID=56 AND SE.FK_REPS_BATCH_ID=466 
    and CASE 
WHEN @FromDate!=NULL AND @ToDate!=NULL     
     THEN dat_STUD_EXAM_FINALEND >= @FromDate AND dat_STUD_EXAM_FINALEND <= @ToDate 
WHEN @FromDate!=NULL AND @ToDate=NULL  
     THEN  dat_STUD_EXAM_FINALEND >= @FromDate  
WHEN @FromDate=NULL AND @ToDate!=NULL  
     THEN  dat_STUD_EXAM_FINALEND <= @ToDate
END
 )   
 strong textGROUP BY RQ.int_REPS_QUES_DIFF_LEVEL

我在

收到错误

THEN dat_STUD_EXAM_FINALEND >= @FromDate AND dat_STUD_EXAM_FINALEND <= @ToDate

这一行请告诉我哪里出错了

Answer 1

而不是

WHEN @FromDate!=NULL AND @ToDate!=NULL

使用

WHEN @FromDate IS NOT NULL AND @ToDate IS NOT NULL

IS [NOT] NULL

如果某些内容为NULL，则在T-SQL中未定义，因此您无法与之进行比较。如果两个（或两个）值中的一个为=，则!=和false都会产生NULL。

Answer 2

请格式化您的查询。阅读会好得多。

SELECT  RQ.int_REPS_QUES_DIFF_LEVEL,
        SUM(1) AS NoOFDificultyQuestion 
FROM    REPS_TEST_QUES_ASSIGNED RQA   
        INNER JOIN REPS_QUESTION RQ 
            ON RQA.int_REPS_TEST_QUES_ASSG_QUESID=RQ.PK_REPS_QUES_ID  
WHERE   int_REPS_TEST_ID IN
        (  
            SELECT  FK_TEST_ID 
            FROM    STUDENT_EXAM SE 
            WHERE   FK_USER_ID=56 
                    AND SE.FK_REPS_BATCH_ID=466 
                    AND (
--If both dates are not NULL then also check dat_STUD_EXAM_FINALEND to be between them
                            (@FromDate IS NOT NULL AND @ToDate IS NOT NULL AND dat_STUD_EXAM_FINALEND >= @FromDate AND dat_STUD_EXAM_FINALEND <= @ToDate )
                            OR
--If @FromDate is not NULL AND @ToDate IS NULL then also check dat_STUD_EXAM_FINALEND to be greater than @FromDate
                            (@FromDate IS NOT NULL AND @ToDate IS NULL AND dat_STUD_EXAM_FINALEND >= @FromDate  )
                            OR
--If @FromDate is NULL AND @ToDate IS NOT NULL then also check dat_STUD_EXAM_FINALEND to be less than @ToDate 
                            (@FromDate IS NULL AND @ToDate IS NOT NULL AND dat_STUD_EXAM_FINALEND <= @ToDate )

--Having AND in each set makes it impossible two sets to be true at the same time. 
--So If both dates are not null the first set will be evaluated. 
--If @ToDate is NULL, then the first and third sets won't be evaluated as they need @ToDate to be not NULL
--If @FromDate is NULL, then the first and second sets won't be evaluated as they need @FromDate to be not NULL
                        )
        ) strongtext GROUP BY RQ.int_REPS_QUES_DIFF_LEVEL

将日期与sql server中的null和datetime值进行比较

2 个答案: