如何在USQL中使用子查询？</p> <pre><code>@CourseDataExcludingUpdatedCourse = SELECT * FROM @CourseData AS cd WHERE cd.CourseID NOT IN (SELECT CourseID FROM @UpdatedCourseData); </code></pre> <p>这不是让我在子查询中使用<code>NOT IN Clause</code>：

Question

我而使用的u-SQL查询follwowing得到complilation错误。我想要显示@UpdatedCourseData中不存在的所有记录。 如何在U-SQL中实现这一点？

Answer 1

以U-SQL NOT EXISTS实现为ANTISEMIJOIN，这样的事情：

@CourseDataExcludingUpdatedCourse = 
    SELECT cd.* 
    FROM @CourseData AS cd 
     ANTISEMIJOIN 
      @UpdatedCourseData AS us 
     ON cd.courseId == us.courseId; 

这里看到更多的信息：

https://msdn.microsoft.com/en-us/library/azure/mt621330.aspx

Answer 2

@employees = 
    SELECT * FROM 
     (VALUES 
     (1, "Noah", 100, (int?)10000, new DateTime(2012,05,31)), 
     (2, "Sophia", 100, (int?)15000, new DateTime(2012,03,19)), 
     (3, "Liam", 100, (int?)30000, new DateTime(2014,09,14)), 
     (4, "Amy", 100, (int?)35000, new DateTime(1999,02,27)), 
     (5, "Justin", 600, (int?)15000, new DateTime(2015,01,12)), 
     (6, "Emma", 200, (int?)8000, new DateTime(2014,03,08)), 
     (7, "Jacob", 200, (int?)8000, new DateTime(2014,09,02)), 
     (8, "Olivia", 200, (int?)8000, new DateTime(2013,12,11)), 
     (9, "Mason", 300, (int?)50000, new DateTime(2016,01,01)), 
     (10, "Ava", 400, (int?)15000, new DateTime(2014,09,14)) 
     ) AS T(EmpID, EmpName, DeptID, Salary, StartDate); 

@departments = 
    SELECT * FROM 
     (VALUES 
     (100, "Engineering"), 
     (200, "HR"), 
     (300, "Executive"), 
     (400, "Marketing"), 
     (500, "Sales"), 
     (600, "Clerical"), 
     (800, "Reserved") 
     ) AS T(DeptID, DeptName); 

/* T-SQL; Using a subquery with IN 
SELECT * 
FROM @employees 
WHERE DeptID IN 
    (SELECT DeptID FROM @departments WHERE DeptName IN ('Engineering', 'Executive')); 
*/ 

// U-SQL; Using SEMIJOIN 
@result = 
    SELECT * 
    FROM @employees AS e 
    LEFT SEMIJOIN (SELECT DeptID FROM @departments WHERE DeptName IN ("Engineering", "Executive")) AS sc 
    ON e.DeptID == sc.DeptID; 

OUTPUT @result 
TO "/Output/ReferenceGuide/Joins/SemiJoins/SubqueryIN.txt" 
USING Outputters.Tsv(outputHeader: true); 

/* T-SQL; Using a subquery with NOT IN 
SELECT * 
FROM @employees 
WHERE DeptID NOT IN 
    (SELECT DeptID FROM @departments WHERE DeptName IN ('Engineering', 'Executive')); 
*/ 

// U-SQL; Using ANTISEMIJOIN 
@result = 
    SELECT * 
    FROM @employees AS e 
    LEFT ANTISEMIJOIN (SELECT DeptID FROM @departments WHERE DeptName IN ("Engineering", "Executive")) AS sc 
    ON e.DeptID == sc.DeptID; 

OUTPUT @result 
TO "/Output/ReferenceGuide/Joins/AntiSemiJoins/SubqueryNOTIN.txt" 
USING Outputters.Tsv(outputHeader: true); 

// BONUS: Switch "LEFT" to "RIGHT" in the above examples and observe the results.