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

Creating and destroying base tables, Creating and Destroying Base Tables: ...

Creating and Destroying Base Tables: Example shows an SQL command to create the base table counterpart of the ENROLMENT variable Example Creating a base table. CREATE T

Built-in functions-comparison operators, Built-In Functions The PL/SQL p...

Built-In Functions The PL/SQL provides a lot of powerful functions to help you to manipulate the data. These built-in functions fall into the categories as shown below: error r

Variable declaration - sql, Variable Declaration - SQL SQL's support f...

Variable Declaration - SQL SQL's support for variables is very similar to Tutorial D's, except that the syntax for creating persistent variables-base tables-is quite differen

Manipulating objects in pl sql, Manipulating Objects: You can use an o...

Manipulating Objects: You can use an object type in the CREATE TABLE statement to indicate the datatype of a column. When the table is created once, you can use the SQL statem

Parameter and keyword description - insert statement, Parameter and Keyword...

Parameter and Keyword Description: table_reference: This identifies a table or view which should be available when you execute the INSERT statement, and for that you sho

Closing a cursor - explicit cursor, Closing a Cursor The CLOSE stateme...

Closing a Cursor The CLOSE statements disable the cursor, and the result set becomes undefined. An illustration of the CLOSE statement as shown: CLOSE c1;

Use of table expressions - expressing constraint conditions, Use of Table E...

Use of Table Expressions - Expressing Constraint Conditions With the exception of key constraints, the examples in the theory book all explicitly reference at least one relvar

CURSOR, #quesWrite a cursor to open an employee database and fetch the empl...

#quesWrite a cursor to open an employee database and fetch the employee record whose age is greater than 45.tion..

Using limit - collection method, Using LIMIT For nested tables, that h...

Using LIMIT For nested tables, that have no maximum size, the LIMIT returns NULL. For varrays, the LIMIT returns the maximum number of elements that a varray can have (that yo

Level - sql pseudocolumns, LEVEL You use the LEVEL with the SELECT CON...

LEVEL You use the LEVEL with the SELECT CONNECT BY statement to categorize rows from a database table into a tree structure. The LEVEL returns the level number of a node in a

Write Your Message!

Name

Email id

Message

Verfication Code

User Account

All Pages