For each of the following pairs of expressions, give instances of relations thatshow the expressions are not equivalent. (r ⟖s)⟖t and r ⟖(s⟖ t) In other words, the natural right outer join is not associative.

What benefits does the GROUPING SETS function offer over traditional GROUP BY clauses?

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Solve the following:

no relatIYCS 3. Give a Z expression for the set of all people in the database who have no siblings in the database. arations through which

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xplain the code below in a step-by-step manner. Also explain what the two join statements intend to achieve.                                                          emp = [(1,"Smith",-1,"2018","10","M",3000), \     (2,"Rose",1,"2010","20","M",4000), \     (3,"Williams",1,"2010","10","M",1000), \     (4,"Jones",2,"2005","10","F",2000), \   ] empColumns = ["emp_id","name","superior_emp_id","year_joined", \        "emp_dept_id","gender","salary"]   empDF = spark.createDataFrame(data=emp, schema = empColumns) empDF.printSchema() empDF.show(truncate=False)   dept = [("Finance",10), \     ("Marketing",20), \     ("Sales",30), \     ("IT",40) \   ] deptColumns = ["dept_name","dept_id"] deptDF = spark.createDataFrame(data=dept, schema = deptColumns) deptDF.printSchema() deptDF.show(truncate=False)   # Join statement 1 empDF.join(deptDF,empDF.emp_dept_id ==  deptDF.dept_id,"outer") \     .show(truncate=False)   # Join statement 2 empDF.join(deptDF,empDF.emp_dept_id ==  deptDF.dept_id,"right")…

it says relation guest doesnt exist am i making a guess table

The following two relations R and S have one attribute storing integers. Assume that a join is performed on this attribute. R = { 4, 3, 1, 6, 2, 9, 0, 5, 8, 7 } S = { 3, 4, 5, 8, 0, 2, 1, 6, 7, 9} Show the order of tuples output for the following join algorithms: (for example Sort Join would give (0,0), (1,1),...,(9,9) ) 1.One pass join where M=12 and R is put in memory: 2.Merge-sort-join with M=5: 3.Hash Join with three buckets and M=4. Assume R is the build relation and S is the probe relation. Also assume bucket 0 is output first. Output:

Course: Principles of Database   please solve it within 30 minutes. please please, pleaseThank you Single Choice Questions 11. Given a relation R and a condition f for selecting from relation R, the correct relational algebraic expression is (    ). A、R X R             B、 R ⋈ R        C、sf(R)                 D、 ∏f(R) 12. If relations R and S have a common attribute set Y, when executing , tuples that do not have matching values on attribute Y will be discarded. To avoid discarding those tuples, which operation should be used? (    ) A. Aggregation.                        B. Grouping. C. Outer union.                        D. Outer join. 13. To address the "lost update" problem, a transaction must obtain (    ) before updating a data set. A. Shared lock (S-lock).               B. Exclusive lock (X-lock). C. Shared lock (S-lock) and exclusive lock (X-lock). D. Shared lock (S-lock) or exclusive lock (X-lock). 14. If, during the system operation, data stored on external storage is…