Microsoft SQL Server Database Quiz Questions

Cardinality in database terminology typically refers to the uniqueness of data in a column, often related to the number of distinct values.

In a one-to-many relationship, each record in the 'one' side can relate to multiple records in the 'many' side, but not vice versa.

Cardinality describes the nature of the relationship between entities, including one-to-one, one-to-many, and many-to-many.

A many-to-many relationship allows multiple records in one table to relate to multiple records in another table.

Cardinality constraints are crucial in defining how tables relate to each other and ensuring data integrity.

Composite primary keys involve multiple columns to uniquely identify records in a table.

A one-to-one relationship ensures that each record in both related tables has exactly one matching record in the other table.

Cardinality determines the number of associations between rows in different tables.

A foreign key constraint enforces referential integrity by requiring that a column's values correspond to values in another table's column.

The cardinality of a relationship can impact query performance due to the way joins and lookups are performed.

Cardinality refers to the nature of relationships between tables, not the number of tables.

Tables can indeed have multiple foreign keys referencing different tables to enforce various relationships.

Foreign key constraints require the referenced table to have a primary key to ensure data integrity.

A junction or intermediate table is used to handle many-to-many relationships by storing pairs of foreign keys.

Cardinality constraints are defined by users during schema design but enforced by the RDBMS.

A one-to-many relationship involves a single record in one table relating to multiple records in another table.

A foreign key is a column or a set of columns in one table that references the primary key in another table.

This describes a many-to-many relationship, where each record can relate to multiple records in both tables.

An intermediate or junction table is used to manage many-to-many relationships between two tables.

A primary key is a unique identifier for a record within a table and cannot contain NULL values.

The FOREIGN KEY constraint is used to establish a link between columns in two tables.

The CASCADE option ensures that changes or deletions in the parent table are automatically propagated to the child table.

In a one-to-one relationship, each record in both tables is related to exactly one record in the other table.

Referential integrity ensures that relationships between tables remain consistent by requiring that foreign keys match primary keys in related tables.

The UNIQUE constraint is used to ensure that all values in a column are distinct across the table.

This describes a self-referencing or recursive relationship, where a table can relate to itself through a foreign key.

A foreign key constraint enforces referential integrity by requiring that a value in one table must match a value in another table's primary key.

To remove a foreign key constraint, you use the ALTER TABLE command with the DROP CONSTRAINT clause.

A one-to-many relationship allows a record in one table to be related to multiple records in another table, but not vice versa.

A composite key is a primary key that consists of more than one column to uniquely identify a record.

A primary key must be unique and cannot contain NULL values. It ensures that each record in a table can be uniquely identified.

Relational databases commonly support one-to-one, one-to-many, and many-to-many relationships between tables.

A foreign key establishes a link between tables by referencing a primary key in another table. It helps maintain referential integrity.

'CASCADE' ensures that changes or deletions in the parent table are reflected in the child table, maintaining referential integrity.

In a many-to-many relationship, multiple records in one table relate to multiple records in another table. This often involves an intermediate table.

Cardinality constraints define the nature of relationships between tables, ensuring proper linkage and integrity of data.

Composite keys involve multiple columns to create a unique identifier for records when a single column is not sufficient.

Self-referencing tables use a foreign key that points to the table's own primary key to establish a hierarchical or recursive relationship.

One-to-one relationships ensure that each record in both related tables corresponds to exactly one record in the other table.

Referential integrity ensures that foreign key values in a table match primary key values in another table, preserving consistent relationships.

High cardinality refers to columns with a large number of unique values relative to the total number of rows. Examples include user IDs or email addresses. High cardinality can impact performance but is useful for indexing.

Low cardinality columns have a limited number of distinct values relative to the total number of rows, such as 'gender' or 'status'. These columns are often less useful for indexing but can be used for grouping and filtering data.

Cardinality affects SQL query performance by influencing the efficiency of indexes and the execution plan. High cardinality columns may benefit from indexing, while low cardinality columns may lead to less efficient queries due to excessive index usage.

Primary keys inherently have high cardinality as they must contain unique values for each record. This high cardinality ensures the integrity and uniqueness of each record in the table.

Selectivity refers to the proportion of rows in a table that satisfy a query condition. High selectivity means that the condition matches few rows, which generally improves query performance by reducing the number of rows processed.