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

Sql, If two relations R and S are joined, then the non matching tuples of b...

If two relations R and S are joined, then the non matching tuples of both R and S are ignored in __________________.

Using not null-declarations in sql, Using NOT NULL Besides assigning an ...

Using NOT NULL Besides assigning an initial value, the declarations can impose the NOT NULL constraint, as the example below shows: acct_id INTEGER(4) NOT NULL := 9999; You ca

I want to build website for funding, Project Description: I want to rebu...

Project Description: I want to rebuild it and add better content to it It will include up to 5 forms The data will be saved on SQL server and the data access layer could b

Do you know anyone that can do this type of coding or not?, Task 2 [12 mark...

Task 2 [12 marks] Write the package body for the following package specification (the detailed description of each function and procedure is provided in the appendix below). Place

Boolean values-assignments in pl/sql, Boolean Values Only the values TRU...

Boolean Values Only the values TRUE, FALSE, & NULL can be assigned to a Boolean variable. For illustration, given the declaration DECLARE done BOOLEAN; the following statements

Aggregate operators sql, Aggregate Operators SQL Supports all of the a...

Aggregate Operators SQL Supports all of the aggregate operators mentioned in the theory book and many more besides. The syntax, however, involves an unusual trick that SQL cal

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?

%isopen - explicit cursor attributes, %ISOPEN The %ISOPEN yields TRUE ...

%ISOPEN The %ISOPEN yields TRUE if its cursor or cursor variable is open; or else, the %ISOPEN yields FALSE. In the illustration, you use the %ISOPEN to select an action:

Inner join, Inner Join We have learned how to retrieve data from one t...

Inner Join We have learned how to retrieve data from one table by using SELECT statement. But, as we have learned, normalized relational databases mean the data is spread betw

Fetching with a cursor, Fetching with a Cursor The FETCH statements re...

Fetching with a Cursor The FETCH statements retrieve the rows in the result set one at a time. After each and every fetch, the cursor advance to the next row in the result set

Write Your Message!

Name

Email id

Message

Verfication Code

User Account

All Pages