Creating a table, PL-SQL Programming

Assignment Help:

Creating a Table

Syantax:

CREATE TABLE ENROLMENT

(StudentId SID,

Name   VARCHAR (30) NOT NULL,

CourseId CID,

PRIMARY KEY (StudentId, CourseId)) ;

Explanation:

  1. CREATE TABLE ENROLMENT announces that what follows defines a variable in the database, named ENROLMENT. A variable in an SQL database is necessarily a table variable, just as in a relational database every variable is a relation variable. SQL does not use the term variable, instead referring to the variable as a base table (its value being called a table, of course).
  2. StudentId SID defines the first column of ENROLMENT, giving its name and either its declared type (a user-defined type) or its domain-we cannot tell which. If SID is a domain, then the definition of that domain specifies the declared type of the column StudentId. Similarly, Name VARCHAR(30) and CourseId CID define the second and third columns of ENROLMENT, respectively. A system-defined type is explicitly given for the column Name but the remarks on the declared type of StudentId apply in similar fashion to CourseId. Note carefully that in SQL it is correct, in ordinary prose, to identify columns by their ordinal position. By contrast there is no such thing as "the first attribute" of a relation or a relation variable.
  3. NOT NULL, appended to the definition of Name, specifies a constraint to the effect that the table assigned to ENROLMENT cannot contain a row in which "the null value of type VARCHAR(30)" appears for that column. The constraint is needed for accurate emulation of Example 2.6 in the theory book because relational theory does not admit any counterpart of SQL's NULL (so nor does Tutorial D). See the next bullet for an explanation of why NOT NULL is not appended to the other two column definitions.
  4. PRIMARY KEY ( StudentId, CourseId ) specifies that at no time can two distinct rows appear in the current value of ENROLMENT having the same value for StudentId and also the same value for CourseId. In enterprise terms, no two enrolments can involve the same student and the same course. In addition, it implies that the NOT NULL constraint applies to each those two columns.

Related Discussions:- Creating a table

Create a procedure that update the status, Create a procedure named STATUS_...

Create a procedure named STATUS_SHIP_SP that allows a company to employee in the Shipping Department to update the status of an order to add shipping information. The BB_BASKETSTAT

Calculate days between ordering and shipping, An analyst in the quality ass...

An analyst in the quality assurance office reviews the time lapse between receiving an order and shipping an order. Any orders that have not been shipped within a day of the order

Named notation, Named Notation The second procedure call uses the name...

Named Notation The second procedure call uses the named notation. An arrow (=>) serve as the relationship operator that associates the formal parameter to the left of the arro

Operator precedence-pl/sql expressions , Operator Precedence The operati...

Operator Precedence The operations within an expression are completed in a particular order depending on their precedence (priority). The table shows the default order of the op

EXCEPTION handling, set serveroutput on declare a number(5); b numb...

set serveroutput on declare a number(5); b number(5); c number(5); begin a:=&a; b:=&b; c:=a/b; dbms_output.put_line(c); exception when zero_divide then d

Indeterminacy in sql, Indeterminacy in SQL Some SQL expressions are ac...

Indeterminacy in SQL Some SQL expressions are actually not function invocations at all in the mathematical sense, being indeterminate-invocations operating on identical input

Keys in sql, Keys in SQL SQL support for keys in the following respect...

Keys in SQL SQL support for keys in the following respects: SQL does not require at least one key for every base table. If no key is explicitly declared, then KEY {ALL B

Features of pl/sql, Main features of PL/SQL A good way to get familiar ...

Main features of PL/SQL A good way to get familiar with PL/SQL is to look at a sample program. The below program processes an order for tennis rackets. At first, it declares a

Oracle PL SQL, I need to write one function and one procedure to query a Or...

I need to write one function and one procedure to query a Oracle 10.1 DB using PL SQL. I have the schema and exact queries...along with work Ive started and a template to put the a

Anatomy of a command, Anatomy of a Command Figure, showing a simple S...

Anatomy of a Command Figure, showing a simple SQL command, is almost identical to its counterpart in the theory book. The only difference arises from the fact that SQL uses a

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