Question

您好我有这样的查询返回过去6个月的注册数据，但是只有至少有1个注册才能显示数据，如何显示没有注册的月份？我知道我可能要对这一行做点什么：

LEFT(CONVERT(varchar, issuedate, 112), 6) BETWEEN 
   LEFT(CONVERT(varchar, DATEADD(MM, -6, GETDATE()), 112), 6) AND 
   LEFT(CONVERT(varchar, GETDATE(), 112), 6)

感谢。

SELECT 
    DateName(month,issuedate) + ' ' + CAST(Year(issuedate) as Char(4)) as IssueDate,
    COUNT(distinct m.ID) AS SignUps
FROM
    Member m 
INNER JOIN 
    Card c ON m.ID = c.MemberID
WHERE 
    m.Deletedby is null 
    AND c.Deletedby is null
    AND LEFT(CONVERT(varchar, issuedate, 112), 6) BETWEEN   
            LEFT(CONVERT(varchar, DATEADD(MM, -6, GETDATE()), 112), 6) 
            AND LEFT(CONVERT(varchar, GETDATE(), 112), 6)
 GROUP BY 
    DateName(month, issuedate) + ' ' + CAST(Year(issuedate) AS  Char(4)), CAST(CAST(YEAR(issuedate) AS VARCHAR) + '/'+ CAST(MONTH(issuedate) AS VARCHAR) +'/1' AS DateTime)

Answer 1

<强>观察：
1.表名并不意味着它们是如何连接的 2.使用你曾经使用过的函数永远不会使用正确的索引 3.所有列引用都应该由表别名限定，以使代码易于理解 4. getdate（）是一个非确定性函数，导致错误的查询计划。将日期传递到sp。

假设当某个成员注册该卡时，会创建Card表中的条目： -

SELECT 
    <month_year_string> as IssueDate,
    COUNT(distinct c.memberid) AS SignUps
FROM
    Member m 
lEFT OUTER JOIN 
    Card c ON m.ID = c.MemberID     AND c.Deletedby is null
WHERE 
    m.Deletedby is null 
    AND c.issuedate BETWEEN  DATEADD(MM, -6, GETDATE()) AND GETDATE()
 GROUP BY <month_year_string>

SQL Server +返回空数据

1 个答案: