Using rename in combination with join - sql, PL-SQL Programming

Assignment Help:

Using RENAME in combination with JOIN - SQL

Example gives pairs of ids of students having the same name, by joining two renamings of IS_CALLED. Example gives an equivalent expression in SQL.

Example: Renaming and joining

Student Sid1 is called Name and so is student Sid2

SELECT *

FROM   (SELECT StudentId AS Sid1, Name FROM IS_CALLED)

     NATURAL JOIN

     (SELECT StudentId AS Sid2, Name FROM IS_CALLED)

As before, the result sagely tells us that student S1 (Anne) has the same name as herself and also shows two pairings of S1 with S5 (both named Boris). The pairing of a student id with itself can be avoided by adding WHERE Sid1 < > Sid2 to the WHERE clause. The duplicate pairings can further be avoided by using < instead of < > in this addition, but that trick assumes that an ordering is defined for type SID, which is not necessarily the case.


Related Discussions:- Using rename in combination with join - sql

Package standard, Package STANDARD The package named STANDARD defines t...

Package STANDARD The package named STANDARD defines the PL/SQL atmosphere. The package specification globally declares the exceptions, types, and subprograms that are available

Create a sql database, The requirements as follows: Create a folder call...

The requirements as follows: Create a folder called "SECURITY" on the server and upload all your project files to that folder. Please note, the "SECURITY" folder is NOT to be IN

Relational shema.., Find the account numbers of all customers whose balance...

Find the account numbers of all customers whose balance is more than 10,000 $

Short-circuit evaluation-pl/sql expressions , Short-Circuit Evaluation ...

Short-Circuit Evaluation When computing a logical expression, the PL/SQL uses short-circuit evaluation. That is, the PL/SQL stops computing the expression as soon as the result

Using %type-declarations in sql, Using %TYPE The %TYPE attribute gives th...

Using %TYPE The %TYPE attribute gives the datatype of a variable or the database column. In the example below, the %TYPE gives the datatype of a variable: credit REAL(7,2); debi

Example of shorthand for a row constraint - sql, Example of Shorthand for a...

Example of Shorthand for a row constraint Example: Shorthand for a row constraint ALTER TABLE EXAM_MARK ADD CONSTRAINT Mark_in_range CHECK (Mark BETWEEN 0 AND 100);

Effects of null for multiple assignments - sql, Effects of NULL for Multipl...

Effects of NULL for Multiple Assignments - SQL If the row expression given as the source for a multiple assignment evaluates to NULL, then NULL is assigned to each target. If

Selecting objects in pl sql, Selecting Objects: Suppose that you have ...

Selecting Objects: Suppose that you have run the SQL*Plus script below that creates object type Person and object table persons, and that you have settled the table: CREATE

Cursor attributes in dynamic sql - pl sql, Using Cursor Attributes: Ev...

Using Cursor Attributes: Every cursor has 4 attributes: %NOTFOUND, %FOUND, %ISOPEN, and %ROWCOUNT. If appended to the cursor name, they return the helpful information about

Semijoin and composition - sql, Semijoin and Composition - SQL For sem...

Semijoin and Composition - SQL For semijoin, the dyadic relational operator MATCHING, defined thus: r1 MATCHING r2, where r1 and r2 are relations such that r1 JOIN r2 is de

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