Database Administration Flashcards

Which SQL keyword is used to sort query results in descending order?

Answer: ORDER BY ... DESC

Adding DESC after a column name in the ORDER BY clause sorts the result set from highest to lowest value for that column.

What does the ACID property 'Durability' guarantee?

Answer: Once committed, a transaction's changes survive system failures

Durability ensures that once a transaction is committed, its changes are permanently saved even if the system crashes immediately afterward.

Which SQL clause is used to combine rows from two SELECT statements into one result set without duplicates?

Answer: UNION

UNION combines the results of two SELECT statements and automatically removes duplicate rows; UNION ALL retains duplicates.

In relational databases, what is referential integrity?

Answer: Guaranteeing that foreign key values always reference valid primary keys

Referential integrity ensures that every foreign key value in a child table corresponds to an existing primary key in the parent table.

What is a database schema?

Answer: The logical structure defining tables, columns, relationships, and constraints

A schema is the logical blueprint of a database, describing the structure of tables, data types, relationships, and constraints without containing actual data.

Which SQL statement is used to grant a user permission to SELECT data from a table?

Answer: GRANT SELECT ON table TO user

The GRANT statement assigns specific privileges such as SELECT, INSERT, or UPDATE to a user or role for a specific database object.

What is the main purpose of database normalization?

Answer: To reduce data redundancy and improve data integrity

Normalization organizes tables to minimize data redundancy, eliminate anomalies, and ensure data is stored logically and consistently.