如何在 USQL 中使用子查询？

Question

我在 u-sql 中使用以下查询时出现编译错误：

@CourseDataExcludingUpdatedCourse = SELECT * FROM @CourseData AS cd 
WHERE cd.CourseID NOT IN (SELECT CourseID FROM @UpdatedCourseData);

它不允许我在子查询中使用 NOT IN Clause。我想显示所有那些不在@UpdatedCourseData 中的记录。我怎样才能在 U-SQL?

中实现这个

Answer 1

在 U-SQL 中 NOT EXISTS 实现为 ANTISEMIJOIN，类似这样：

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

查看此处了解更多信息：

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.

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