Using aggregation on nested tables - sql, PL-SQL Programming

Assignment Help:

Using Aggregation on Nested Tables

Example is the most direct translation of its counterpart in the theory book that can be obtained in SQL but it is so over-elaborate that no SQL practitioner would consider using it. It uses the aggregate operator COUNT on the table values for column ExamResult to obtain the number of students who sat each exam. Unfortunately, as already noted, we cannot operate directly on ExamResult as a FROM clause element. Instead, we need to use an artifice that is specially devised for the sake of this example.

Example: How many students sat each exam

WITH C_ER AS (

 SELECT CourseId,

 CAST (

 TABLE (SELECT DISTINCT StudentId, Mark

 FROM EXAM_MARK AS EM

 WHERE EM.CourseId = C.CourseId)

 AS ROW ( StudentId SID, Mark INTEGER ) MULTISET)

 AS ExamResult

 FROM COURSE AS C)

SELECT CourseId, (SELECT COUNT (*)

FROM TABLE (ER (ExamResult)) AS t) AS n

FROM C_ER


Related Discussions:- Using aggregation on nested tables - sql

Select query, Query: SELECT * FROM EMPLOYEE1; Select 5 columns and ...

Query: SELECT * FROM EMPLOYEE1; Select 5 columns and all rows from one table Query: SELECT C_ID, COMPANY, BUILDING, DEPARTMENT, BRANCH FROM CONTRACT;

Logical connectives - sql, Logical Connectives - SQL SQL's extended t...

Logical Connectives - SQL SQL's extended truth tables in which the symbol, for unknown, appears along with the usual T and F. Negation (NOT, ¬) Conjunction (

Union without corresponding - sql, UNION without CORRESPONDING - SQL T...

UNION without CORRESPONDING - SQL The use of UNION without CORRESPONDING. Example is merely by omitting CORRESPONDING, but only because the operands have identical SELECT clau

Introduction to SQl and DQL, which operation is used if we are interested i...

which operation is used if we are interested in only certain columns of a table?

Operator precedence-pl/sql expressions , Operator Precedence The operati...

Operator Precedence The operations within an expression are completed in a particular order depending on their precedence (priority). The table shows the default order of the op

Database values-assignments in pl/sql, Database Values You can use the S...

Database Values You can use the SELECT statement to have the Oracle assign values to a variable. For Each and every item in the select list, there must be a matching, type-compa

Exit statement - syntax, EXIT Statement   You can use the EXIT stateme...

EXIT Statement   You can use the EXIT statement to exit a loop. The EXIT statement has 2 forms: the conditional EXIT WHEN and the unconditional EXIT. With the either form, you

Use of table comparisons - sql, Use of Table Comparisons - SQL Table ...

Use of Table Comparisons - SQL Table comparisons where it is noted that although table expressions cannot be compared, we have TABLE (t) to convert a table expression t into

Anatomy of a command, Anatomy of a Command Figure, showing a simple S...

Anatomy of a Command Figure, showing a simple SQL command, is almost identical to its counterpart in the theory book. The only difference arises from the fact that SQL uses a

In out mode - parameter modes, IN OUT Mode An IN OUT parameter passes ...

IN OUT Mode An IN OUT parameter passes initial values to the subprogram being called and return efficient values to the caller. Within the subprogram, an IN OUT parameter acts

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd