Adding table constraints, PL-SQL Programming

Assignment Help:

Adding Table Constraints

ALTER TABLE ENROLMENT ADD CONSTRAINT NameNotNull

CHECK (Name IS NOT NULL) ;

ALTER TABLE ENROLMENT ADD CONSTRAINT PK_StudentId_CourseId

PRIMARY KEY (StudentId, CourseId) ;

  1. ALTER TABLE ENROLMENT specifies that the definition of base table ENROLMENT is to be modified in some way, such as adding or dropping a column, adding or dropping a constraint (among other things).
  2. ADD CONSTRAINT NameNotNull specifies that in fact a constraint is being added to the definition of ENROLMENT, and the name by which that constraint can subsequently be referred to is NameNotNull. For example, the name would be needed if the constraint were later to be dropped, or perhaps it could appear in an error message when an attempted update is rejected for violating that constraint. Similar comments apply to ADD CONSTRAINT PK_StudentId_CourseId.
  3. CHECK (Name IS NOT NULL) specifies a truth-valued expression, Name IS NOT NULL, that must be satisfied by each row of every table that is assigned to ENROLMENT. If the current value of ENROLMENT fails to satisfy this constraint, then the ALTER TABLE statement fails.
  4. PRIMARY KEY ( StudentId, CourseId ) used for constraint. Again, the ALTER TABLE statement fails if the constraint is not satisfied by the current value of ENROLMENT.

Related Discussions:- Adding table constraints

Check constraints in sql, CHECK Constraints in SQL A CHECK constraint ...

CHECK Constraints in SQL A CHECK constraint is a table constraint defined using the key word CHECK, as already illustrated in several examples in this chapter. In particular,

Expression in assignment statement - pl sql, Expression: This is a ran...

Expression: This is a randomly complex combination of constants, variables, literals, operators, & function calls. The simplest expression consists of a single variable. If th

Cartesian product, Using a Join on 2 tables, select all columns and all row...

Using a Join on 2 tables, select all columns and all rows from the tables without the use of a Cartesian product. Query: SELECT * FROM EMPLOYEE1 JOIN CONTRACT ON EMPLOYEE

Semidifference and not - sql, Semidifference and NOT - SQL In this sec...

Semidifference and NOT - SQL In this section first describe the relational difference operator, named MINUS. Example here shows SQL's closest counterpart of that operator.

Name resolution - pl/sql, Name Resolution   During the compilation, th...

Name Resolution   During the compilation, the PL/SQL compiler relates identifiers like the name of a variable with an address or memory location, actual value, or datatype. Th

Object types - syntax, Object Types An object type is a user-defined co...

Object Types An object type is a user-defined complex datatype which encapsulates the data structure along with the functions and procedures required to manipulate the data. Th

Positional and named notation, Positional and Named Notation You can wr...

Positional and Named Notation You can write the actual parameters when calling a subprogram, using either positional or named notation. That is, you can point to the relationsh

Oracle 9i features, Bitmap Join Indexes - This feature will increase th...

Bitmap Join Indexes - This feature will increase the performance and detains the size and format of your databases in data Character Semantics and Globalization -This featur

Introduction to oracle, Introduction Oracle 9i - it was made publ...

Introduction Oracle 9i - it was made public in the year 2001 with over 400 features, and graphics, it has merged the traditional business with modern internet application

Assignment source not a literal - variable, Assignment Source Not a Literal...

Assignment Source Not a Literal - Variable Syntax: SET SN = SID (SUBSTRING (SN.C FROM 1 FOR 1)||'5');

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