Explain how to check which version of a database/SQL a database is using. What does it mean when programmers say tables are not normalized? What is the difference between an associative entity and a transactional entity? What does SQL stand for? The UNIQUE constraint differs fr...
Describe the SQL clauses used in the definition of: a primary key constraint, an alternate key constraint, a foreign key constraint, a check constraint. Describe the importance of the relational data model or entity-relationship model. What is the significance of 3-tier architecture when discussin...
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The constraint is also restricting the facts that can be saved in the relations. They are applied to verify the province’s performance and to keep it protected. The Main Principles Of The RDBMS Model are: Entity integrity: Entity integrity says that in a database, all the data should be ...
A key is one or more columns that are identified as such in the creation of a table or index, or in the definition of referential integrity. Primary key A table can only have one primary key because it defines the entity. There are two requirements for a primary key: ...
The following two integrity constraints must be supported.(a)Entity Integrity: No component of primary key is allowed to have anull value.(b)Referential integrity: For each distinct non-null foreign key value in a relationaldatabase,there must exist a matching primary key from the same range ...
integrity must be maintained before every transaction is completed. If a key constraint is enforced to uniquely identify an entity within a table (such as the CUSTOMER_ID), if a new entity with the same ID is created the transaction will be prevented to ensure referential integrity is ...
User-defined integrityacts as a way to catch errors which domain, referential and entity integrity do not. Here, you define your own specific business rules and constraints which trigger automatically when predefined events occur. For instance, you could define the constraint that customers must resi...
The NULL value in the table means the field with “space”. It is different if it is filled as ‘0’ or if it contains space. Data Integrity: There are few categories of data integrity with each RDBMS: · Entity integrity: This specifies that there should be no duplicate rows in a ta...
Physical Role: The primary key is a specific implementation of the entity identifier when the database is created. It is a physical constraint defined in the database schema. Purpose: The primary key ensures that each row in a database table is unique and enforces the integrity of the data...