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

Initializing records, Initializing Records The illustration below show...

Initializing Records The illustration below shows that you can initialize a record in its type definition. Whenever you declare a record of the type TimeRec, its 3 fields supp

Python function, This task involves developing some functions that extract ...

This task involves developing some functions that extract data from an SQL database. The scenario is that a company which owns an online vehicle search website wants to generate so

Cursor for loops, Cursor FOR Loops In most cases that need an explicit ...

Cursor FOR Loops In most cases that need an explicit cursor, you can simplify the coding by using a cursor FOR loop rather of the OPEN, FETCH, and CLOSE statements. A cursor FO

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

Primary key - sql, Primary Key - SQL A PRIMARY KEY specification carri...

Primary Key - SQL A PRIMARY KEY specification carries an implicit NOT NULL constraint on each column of the specified key. When more than one key constraint is required, the k

Using cursor attributes - bulk bind performance improvement, Using Cursor A...

Using Cursor Attributes To process the SQL data manipulation statements, the SQL engine must opens an implicit cursor named SQL. This cursor's attributes (%FOUND, %NOTFOUND, %

Name resolution-naming conventions, Name Resolution In potentially uncer...

Name Resolution In potentially uncertain SQL statements, the names of the database columns take precedence over the names of the local variables and formal parameters. For e.g.

Effect of anonymous columns, Effect of Anonymous Columns Now, recall t...

Effect of Anonymous Columns Now, recall that a VALUES expression denotes a table with undefined column names. If an initial value is to be specified when a base table is creat

Calculate the total shopper spending, Many of the reports generated from th...

Many of the reports generated from the system calculate the total dollars in purchases for a shopper. Complete the following steps to create a function named TOT_PURCH_SF that acce

Parameter aliasing, Parameter Aliasing To optimize the subprogram ca...

Parameter Aliasing To optimize the subprogram call, the PL/SQL compiler can decide between the two techniques of the parameter passing. With the by-value techniques, the v

Write Your Message!

Name

Email id

Message

Verfication Code

User Account

All Pages