Effects of null for unique specification

Effects of null for unique specification - sql, PL-SQL Programming

Assignment Help:

Effects of NULL for UNIQUE Specification

When a UNIQUE specification u for base table t includes a column c that is not subject to a NOT NULL constraint, the appearance of several rows having NULL in place of a value for c and equal values for the other columns specified in u is permitted. It is only when each column of the specified "key" has a value that those column values may not appear in the same combination in more than one row of t.

Related Discussions:- Effects of null for unique specification - sql

Need azure crm web application with authentication, Need Azure CRM Web Appl...

Need Azure CRM Web Application with two-factor authentication We presently have a CRM-like database stored on MS Azure that we presently access over an MS Access application. It

Benefit of the dynamic sql pl sql, Benefit of the dynamic SQL: This pa...

Benefit of the dynamic SQL: This part shows you how to take full benefit of the dynamic SQL and how to keep away from some of the common pitfalls. Passing the Names of Sc

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

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.

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

Commit statement in pl sql, COMMIT Statement The COMMIT statement expli...

COMMIT Statement The COMMIT statement explicitly makes everlasting changes to the database during the present transaction. The Changes made to the database are not considered e

Use of count in sql, Use of COUNT in SQL It describes and discusses va...

Use of COUNT in SQL It describes and discusses various general methods of expressing constraints, eventually noting that support for "=" with relation operands is sufficient f

Built-in functions-comparison operators, Built-In Functions The PL/SQL p...

Built-In Functions The PL/SQL provides a lot of powerful functions to help you to manipulate the data. These built-in functions fall into the categories as shown below: error r

Declaring subprograms, Declaring Subprograms You can declare subprog...

Declaring Subprograms You can declare subprograms in any PL/SQL subprogram, block, or package. But, you should declare subprograms at the end of the declarative part after a

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

Write Your Message!

Name

Email id

Message

Verfication Code

User Account

All Pages