Keys in sql, PL-SQL Programming

Assignment Help:

Keys in SQL

SQL support for keys in the following respects:

  1. SQL does not require at least one key for every base table. If no key is explicitly declared, then KEY {ALL BUT} is implicit.
  2. When no key is specified there is no prohibition on multiple appearances of the same row.
  3. SQL does not recognize the empty set as a key.
  4. SQL allows a key to be a proper superset of another key for the same base table. (This "feature" is sometimes used as a workaround for the fact that the columns of the foreign key are required to correspond to those of a declared key of the referenced table.)

Related Discussions:- Keys in sql

Exit-when - iterative control, EXIT-WHEN The EXIT-WHEN statement permits...

EXIT-WHEN The EXIT-WHEN statement permits a loop to complete conditionally. Whenever the EXIT statement is encountered, the condition in the WHEN clause is computed. When the co

Block structure in pl/sql, Block Structure The PL/SQL is a block-struct...

Block Structure The PL/SQL is a block-structured language. That is, the fundamental units (procedures, anonymous blocks, and functions) that make up a PL/SQL program are logi

Advantages of exceptions, Advantages of Exceptions Using the exception...

Advantages of Exceptions Using the exceptions for the error handling has many benefits. Without an exception handling, every time you issue a command, you should ensure for th

Object types and collections - performance of application, Use Object Types...

Use Object Types and Collections The Collection types and object types increase your efficiency by allowing for the realistic data modeling. The Complex real-world entities an

Parameter and keyword description - object types, Parameter and Keyword Des...

Parameter and Keyword Description: type_name: This identifies a user-defined type specifier that is used in the subsequent declarations of the objects. AUTHID Clause:

Pl sql code to declare cursors with parameter, Write a pl/sql block that de...

Write a pl/sql block that declares and uses cursors with parameters. In a loop, use a cursor to retrieve the department number and the department name from the departments table

Procedure, 1. Create a procedure called TAX_COST_SP to accomplish the tax c...

1. Create a procedure called TAX_COST_SP to accomplish the tax calculation task. Keep in mind that the state and subtotal values are inputs into the procedure and the procedure is

Effects of null operator, Effects of NULL Operator As a general rule-b...

Effects of NULL Operator As a general rule-but not a universal one-if NULL is an argument to an invocation of a system-defined read-only operator, then NULL is the result of t

I want database development with analysis tools, Project Description: I ...

Project Description: I want a database for large governmental and private data sets on one country that will be easily extended to other countries in the future. Also, the datab

Testing triggers, Demonstrate your knowledge of PL/SQL programming by writi...

Demonstrate your knowledge of PL/SQL programming by writing and thoroughly testing triggers and stored procedures associated with an e-commerce application that provides security l

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