Question

我必须检查任何书籍ID和/或书籍代码是否与唯一的StudentVisitId重复，并且它应该返回单行。如果找到重复，那么它应该返回0，否则为1。

数据：

BookID  StudentVisitId  BookCode    ListOrder
42568   4531            B1162       3
42568   4531            B1162       2
64532   4531            B1178       2
64532   4598            B1178       3
76543   4622            B1178       2
64532   4622            B1178       1

预期输出：

StudentVisitId  DuplicateEntry
4531            0
4598            1
4622            1

0表示StudentVisitId 4531与BookId 42568和BookCode B1162重复。

Answer 1

这可以通过多种方式完成。下面的SQL显示了如何使用CTE实现此目的

;
WITH CTE(StudentVisitId, DuplicateEntry)
AS
(
SELECT StudentVisitId,
       CASE 
       WHEN ROW_NUMBER() OVER (PARTITION BY BookId, StudentVisitId, BookCode ORDER BY StudentVisitId) > 1 
       THEN 0 ELSE 1 
       END 
FROM LibraryData
)SELECT StudentVisitId, MIN(DuplicateEntry) FROM cte 
GROUP BY StudentVisitId

Answer 2

如果我理解正确：

categories

我不确定select studentid, (case when min(bookcode) = max(bookcode) then 1 else 0 end) as isDuplicate from t group by studentid;在这种情况下的真正意义。这似乎是专栏的奇怪名称。更好的名称是isDuplicate。

Answer 3

你可以试试这个

SELECT StudentVisitId, MIN(DuplicateEntry) DuplicateEntry
FROM (
    SELECT BookID,  StudentVisitId,  BookCode, DuplicateEntry = (CASE WHEN COUNT(*) > 1 THEN 0 ELSE 1 END)
    FROM @DATA
    GROUP BY BookID,  StudentVisitId,  BookCode 
) AS A
GROUP BY StudentVisitId

SQL：在库数据库中查找重复条目

3 个答案: