Example of groupby operator - sql, PL-SQL Programming

Assignment Help:

Example of GROUPBY Operator

Example: How many students sat each exam,

using GROUP BY, NATURAL LEFT JOIN, and COALESCE

SELECT CourseId, COALESCE (n, 0) AS n

FROM COURSE NATURAL LEFT JOIN

(SELECT CourseId, COUNT (*) AS n

FROM EXAM_MARK

GROUP BY CourseId) AS T

Explanation

NATURAL JOIN: Note, however, that the use of LEFT makes this an outer join, whereas Codd's term natural join referred to the "inner" variety only.
LEFT specifies that each unmatched row in the first join operand, COURSE, is to be extended with NULL for the column n.
COALESCE (n, 0) AS n effectively replaces those appearances of NULL by the correct value, 0.

Related Discussions:- Example of groupby operator - sql

Write sql queries, Write SQL queries to solve the following specifications....

Write SQL queries to solve the following specifications. Include the query AND THE OUTPUT. A screen dump of the output is acceptable. Show as many rows as you can. A screen dump i

Passing cursor parameters, Passing Cursor Parameters You use the OPEN ...

Passing Cursor Parameters You use the OPEN statement to pass the parameters to a cursor. Unless you want to accept the default values, each proper parameter in the cursor decl

Packaging cursors, Packaging Cursors You can split a cursor specific...

Packaging Cursors You can split a cursor specification from its body for placement in a package. In that way, you can change the cursor body without changing the cursor spec

Using operator ref - manipulating objects pl sql, Using Operator REF: ...

Using Operator REF: You can retrieve refs by using the operator REF that, like VALUE, takes as its argument a correlation variable. In the illustration below, you retrieve one

I need sql to infopath data connection, I need SQL to infopath data connect...

I need SQL to infopath data connection Project Description: Want data retrieval connection from SQL to SharePoint infopath Skills required are Sharepoint, SQL

Parameter and keyword description - exit statement, Parameter and Keyword D...

Parameter and Keyword Description: EXIT: An unconditional EXIT statement (i.e., one without a WHEN clause) exits the present loop instantly. The Execution resumes with th

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

Recursion versus iteration, Recursion versus Iteration Dissimilar the i...

Recursion versus Iteration Dissimilar the iteration, recursion is not crucial to PL/SQL programming. Any problem which can be solved using recursion can be solving using the it

Dynamic ranges- iterative control, Dynamic Ranges The PL/SQL lets you det...

Dynamic Ranges The PL/SQL lets you determine the loop range dynamically at run time, as the example below shows: SELECT COUNT(empno) INTO emp_count FROM emp; FOR i IN 1..emp_cou

Parameter and keyword description - open-for statement, Parameter and Keywo...

Parameter and Keyword Description: cursor_variable_name: This identifies a cursor variable or the parameter formerly declared within the present scope. host_cursor_va

Write Your Message!

Name

Email id

Message

Verfication Code

User Account

All Pages