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

Semidifference via not in and a subquery , Semidifference via NOT IN and a ...

Semidifference via NOT IN and a subquery SELECT StudentId FROM IS_CALLED WHERE Name = 'Devinder' AND StudentId NOT IN (SELECT StudentId FROM IS_ENROLLED_ON WHER

Ending transactions, Ending Transactions A good quality programming pr...

Ending Transactions A good quality programming practice is to commit or roll back every transaction explicitly. Whether you rollback or issue the commit in your PL/SQL program

Example of alternative formulation as a table constraint, Example of Altern...

Example of Alternative formulation as a table constraint Example: Alternative formulation as a table constraint ALTER TABLE EXAM_MARK ADD CONSTRAINT Must_be_enrolled_to_

Example of add constraint in sql, Example of ADD CONSTRAINT in SQL Exa...

Example of ADD CONSTRAINT in SQL Example: Alternative formulation for MAX_ENROLMENTS ALTER TABLE IS_ENROLLED_ON ADD CONSTRAINT MAX_ENROLMENTS CHECK ((SELECT COUNT (*)

Blocks, Blocks: The fundamental program unit in the PL/SQL is the bloc...

Blocks: The fundamental program unit in the PL/SQL is the block. The PL/SQL block is defined by the keywords BEGIN, DECLARE, EXCEPTION, and END. These keywords partition the b

Example of when or then constraints - sql, Example of WHEN or THEN Constrai...

Example of WHEN or THEN Constraints A concrete example showing how SQL supports WHEN/THEN constraints CREATE TABLE SAL_HISTORY (EmpNo CHAR (6), Salary INTEGER NOT NULL,

Substitution and instantiation - sql, Substitution and Instantiation - SQL ...

Substitution and Instantiation - SQL It shows how NULL might appear in substitution for a parameter of a predicate and how it might thus participate in instantiation of that p

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

Keyword, what is the use of declare keyword

what is the use of declare keyword

Difference between ttitle and btitle, TTITLE and BTITLE are commands in Pl-...

TTITLE and BTITLE are commands in Pl-SQL to control report headings and footers. This Ttitle & Btitle are mainly used on creating SQL*PLUS report. Ttitle is used for toptitle headi

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