Example of cast operator - sql, PL-SQL Programming

Assignment Help:

Example of Cast Operator

So long as CAST is used as shown, we could obtain the total marks for each exam in similar fashion, using SUM (Mark) AS TotalMarks. However, this gives NULL, instead of zero, for the courses whose exams nobody sat. That problem can be addressed by using COALESCE, as shown in Example.

Example: Give the total of marks for 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 SUM (Mark)

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

FROM C_ER

Explanation

  • COALESCE((SELECT SUM(Mark) FROM TABLE(ER(ExamResult)) AS t),0) yields the value of the scalar subquery whenever ExamResult is nonempty, otherwise zero. SQL's COALESCE is an n-adic operator that takes a commalist of expressions of the same declared type and yields the result of the first of those expressions, in the order in which they are written, that does not evaluate to NULL. When there is no such operand, it yields NULL anyway, of course.

Related Discussions:- Example of cast operator - sql

Example of cast operator - sql, Example of Cast Operator So long as C...

Example of Cast Operator So long as CAST is used as shown, we could obtain the total marks for each exam in similar fashion, using SUM (Mark) AS TotalMarks. However, this giv

Projection and existential quantification - sql, Projection and Existential...

Projection and Existential Quantification - SQL Intuitively it might seem that projection in SQL is simply a matter of specifying the required columns in the SELECT clause, a

Data type conversion, Datatype Conversion At times it is necessary to c...

Datatype Conversion At times it is necessary to convert a value from one datatype to another. For e.g. if you want to inspect a rowid, you should convert it to a character stri

Declaring a cursor, Declaring a Cursor The Forward references are not ...

Declaring a Cursor The Forward references are not allowed in the PL/SQL. Therefore, you must declare a cursor before referencing it in other statements. Whenever you declare a

Write a program, to write a heap sort program usin pl-sql

to write a heap sort program usin pl-sql

Declaring and initializing objects in pl/sql, Declaring and Initializing Ob...

Declaring and Initializing Objects: An object type is once defined and installed in the schema; you can use it to declare the objects in any PL/SQL, subprogram, block or packa

Example of when or then constraints - sql, Example of WHEN or THEN Constrai...

Example of WHEN or THEN Constraints A concrete example showing how SQL supports WHEN/THEN constraints CREATE TABLE SAL_HISTORY (EmpNo CHAR (6), Salary INTEGER NOT NULL,

Overview of control structures-comparison operators, Overview of control st...

Overview of control structures According to the structure theorem, any computer program can be written by using the basic control structures as shown in figure below. They can b

If statement - syntax, IF Statement The IF statement executes a series ...

IF Statement The IF statement executes a series of statement conditionally. Whether the series is executed or not depends on the value of the Boolean expression. Syntax:

For-loop -iterative control, FOR-LOOP While the number of iterations thr...

FOR-LOOP While the number of iterations through a WHILE loop is unknown till the loop completes, then the number of iterations through a FOR loop is known before the loop is ent

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