Sql server 是否使用SQL Server查询从考勤日志表和员工表中获取空值？

我有这样的查询来提取数据：

SELECT 
    e.EmpName,
    d.DepartmentName,
    l.EnrollNumber,
    v.VerifyModeName,
    CAST(PunchTime as DATE)Check_Date,MIN(CAST(PunchTime as Time))[TimeIN], MAX(Cast(PunchTime as Time))[TimeOUT],
        RIGHT('0' + CAST(DATEDIFF(SECOND, MIN(CAST(PunchTime as Time)), MAX(Cast(PunchTime as Time))) / 3600 AS VARCHAR),2) + ':' +
        RIGHT('0' + CAST((DATEDIFF(SECOND, MIN(CAST(PunchTime as Time)), MAX(Cast(PunchTime as Time))) / 60) % 60 AS VARCHAR),2)  + ':' +
        RIGHT('0' + CAST(DATEDIFF(SECOND, MIN(CAST(PunchTime as Time)), MAX(Cast(PunchTime as Time))) % 60 AS VARCHAR),2) as Duration
FROM 
    Department d, 
    VerifyModes v, 
    Employee e 
FULL OUTER JOIN AttLog l 
    ON e.EnrollNumber=l.EnrollNumber
WHERE
    e.DeptID = d.Id
    AND l.VerifyMode = v.VerifyModeId 
GROUP BY 
    e.EmpName, d.DepartmentName, l.EnrollNumber, v.VerifyModeName, CAST(PunchTime as DATE)
ORDER BY Check_Date

结果如下：

SELECT 
    e.EmpName,
    d.DepartmentName,
    l.EnrollNumber,
    v.VerifyModeName,
    CAST(PunchTime as DATE)Check_Date,MIN(CAST(PunchTime as Time))[TimeIN], MAX(Cast(PunchTime as Time))[TimeOUT],
        RIGHT('0' + CAST(DATEDIFF(SECOND, MIN(CAST(PunchTime as Time)), MAX(Cast(PunchTime as Time))) / 3600 AS VARCHAR),2) + ':' +
        RIGHT('0' + CAST((DATEDIFF(SECOND, MIN(CAST(PunchTime as Time)), MAX(Cast(PunchTime as Time))) / 60) % 60 AS VARCHAR),2)  + ':' +
        RIGHT('0' + CAST(DATEDIFF(SECOND, MIN(CAST(PunchTime as Time)), MAX(Cast(PunchTime as Time))) % 60 AS VARCHAR),2) as Duration
FROM 
    Department d, 
    VerifyModes v, 
    Employee e 
FULL OUTER JOIN AttLog l 
    ON e.EnrollNumber=l.EnrollNumber
WHERE
    e.DeptID = d.Id
    AND l.VerifyMode = v.VerifyModeId 
GROUP BY 
    e.EmpName, d.DepartmentName, l.EnrollNumber, v.VerifyModeName, CAST(PunchTime as DATE)
ORDER BY Check_Date

尽管我已经包含了

完全外部连接

条件

如果我只使用：

select e.EmpName, l.PunchTime 
from Employee e 
full outer join AttLog l 
    on e.EnrollNumber = l.EnrollNumber

结果显示

Employee

和

NULL

PunchTime

：

那么，如何修复上述查询以获得包含

NULL

PunchTime

的结果呢

然后，当我添加日期条件时，查询仍然不会再次显示NULL。如何纠正

SELECT 
            e.EmpName,
            d.DepartmentName,
            l.EnrollNumber,
            v.VerifyModeName,
            CAST(PunchTime as DATE)Check_Date,MIN(CAST(PunchTime as Time))[TimeIN], MAX(Cast(PunchTime as Time))[TimeOUT],
                RIGHT('0' + CAST(DATEDIFF(SECOND, MIN(CAST(PunchTime as Time)), MAX(Cast(PunchTime as Time))) / 3600 AS VARCHAR),2) + ':' +
                RIGHT('0' + CAST((DATEDIFF(SECOND, MIN(CAST(PunchTime as Time)), MAX(Cast(PunchTime as Time))) / 60) % 60 AS VARCHAR),2)  + ':' +
                RIGHT('0' + CAST(DATEDIFF(SECOND, MIN(CAST(PunchTime as Time)), MAX(Cast(PunchTime as Time))) % 60 AS VARCHAR),2) as Duration
        FROM Department d    
        INNER JOIN Employee e
            ON e.DeptID = d.Id
        LEFT JOIN AttLog l 
            ON e.EnrollNumber = l.EnrollNumber
        LEFT JOIN VerifyModes v
            ON l.VerifyMode = v.VerifyModeId 
        WHERE cast(l.PunchTime as Date) between '2015-07-22' and '2015-07-22'
        GROUP BY 
            e.EmpName, d.DepartmentName, l.EnrollNumber, v.VerifyModeName, CAST(PunchTime as DATE)

        ORDER BY Check_Date

---

尝试使用

左连接

：

SELECT 
    e.EmpName,
    d.DepartmentName,
    l.EnrollNumber,
    v.VerifyModeName,
    CAST(PunchTime as DATE)Check_Date,MIN(CAST(PunchTime as Time))[TimeIN], MAX(Cast(PunchTime as Time))[TimeOUT],
        RIGHT('0' + CAST(DATEDIFF(SECOND, MIN(CAST(PunchTime as Time)), MAX(Cast(PunchTime as Time))) / 3600 AS VARCHAR),2) + ':' +
        RIGHT('0' + CAST((DATEDIFF(SECOND, MIN(CAST(PunchTime as Time)), MAX(Cast(PunchTime as Time))) / 60) % 60 AS VARCHAR),2)  + ':' +
        RIGHT('0' + CAST(DATEDIFF(SECOND, MIN(CAST(PunchTime as Time)), MAX(Cast(PunchTime as Time))) % 60 AS VARCHAR),2) as Duration
FROM Department d    
INNER JOIN Employee e
    ON e.DeptID = d.Id
LEFT JOIN AttLog l 
    ON e.EnrollNumber = l.EnrollNumber
LEFT JOIN VerifyModes
    ON l.VerifyMode = v.VerifyModeId 
GROUP BY 
    e.EmpName, d.DepartmentName, l.EnrollNumber, v.VerifyModeName, CAST(PunchTime as DATE)
ORDER BY Check_Date

---

注:

---

编辑： 将日期比较放在

WHERE

子句中，而不是放在

JOIN

条件中：

LEFT JOIN Attlog l
    ON e.DeptID = d.Id
    AND cast(l.PunchTime as Date) between '2015-07-22' and '2015-07-22'

---

将比较放在

WHERE

子句中，将查询转换为

内部联接

，从而删除

NULL

行。

如果我为查询添加日期条件，请提供帮助，它仍然不会显示谁的PunchTime为空。将日期放在

JOIN

条件中，而不是

WHERE

子句中。我将WHERE替换为“JOIN cast（l.PunchTime as DATE）介于'2015-07-22'和'2015-07-22'之间”，但得到错误：关键字'as'附近的语法不正确。没有问题，很高兴我能帮忙。把日期比较放在

ON

子句中。