Quick Revision

GK One-Line Question & Answer

15541+ short questions with short answers, covering every category and sub-category on the site — no long articles to scroll through. Good for a fast recap before an exam, or a few minutes of daily practice.

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DBMS → Introduction to DBMS 31

Database auditing records
ALL database activity (who did what, when, from where)
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Data masking replaces
Sensitive real data with realistic-looking but fictitious data for non-production use
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Data warehouse is characterized by
Subject-oriented, integrated, time-variant, non-volatile collection for decision support
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OLAP is optimized for
Complex analytical queries on large historical datasets
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Star schema fact table contains
Numeric measures + foreign keys to dimension tables
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ETL stands for
Extract Transform Load
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CAP theorem: during network partition choose between
Consistency OR Availability (cannot guarantee both)
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Sharding distributes
Table rows across multiple database servers based on a shard key
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NoSQL database best for social graph traversal
Graph database (Neo4j, Neptune)
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Recursive CTE requires
BASE CASE (anchor member) AND RECURSIVE CASE
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PERCENT_RANK() of highest-ranked row is
0.0
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SUM(salary) OVER(ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) computes
Running cumulative total of salary
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CUME_DIST() computes
Cumulative distribution: fraction of rows ≤ current row value
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ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING includes
Previous row + current row + next row (3-row window)
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PAXOS consensus protocol is used in
Distributed systems for fault-tolerant consensus among multiple nodes
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Base property of NoSQL - Eventually consistent means
Given enough time (no updates) all replicas will converge to same value
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Vertical fragmentation in distributed DB divides relation by
Columns (attributes) keeping PK in each fragment
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Horizontal fragmentation in distributed DB divides relation by
Rows (subsets of tuples) based on selection predicates
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Location transparency in distributed DB means
User can query data without knowing its physical location
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Impedance mismatch in databases refers to
Mismatch between OO programming model and relational data model
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ORM (Object-Relational Mapper) bridges
Object-oriented programming model and relational database (impedance mismatch)
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Laravel's Eloquent uses which ORM pattern?
Active Record pattern
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Which SQL function returns current date only (no time)?
CURDATE() or CURRENT_DATE
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FLOOR(4.9) returns
4
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CEIL(4.1) returns
5
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ROUND(4.567,2) returns
4.57
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ABS(-15) returns
15
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MOD(17,5) returns
2
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UPPER('dbms') returns
DBMS
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LOWER('DBMS') returns
dbms
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LENGTH('RMSSSB') returns
6
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DBMS → Views 2

Materialized view differs from regular view because
It physically stores query results and can be refreshed periodically
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WITH CHECK OPTION on updatable view ensures
Updates through view MUST satisfy view's WHERE condition
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DBMS → PL/SQL 2

INSTEAD OF trigger on a view
Intercepts DML on views and executes custom logic replacing the standard DML
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Stored procedures improve security by
Allowing users to call procedure without direct table access (execute-only permission)
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DBMS → SQL Basics 3

ROLLUP in GROUP BY
Generates subtotals and grand total across hierarchy levels
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CUBE in GROUP BY
Generates subtotals for ALL possible combinations of specified grouping columns
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NTILE(4) OVER(ORDER BY salary) divides
Ordered rows into 4 approximately equal-sized buckets
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DBMS → Transactions 1

Two-Phase Commit (2PC) is used for
Distributed database transactions across multiple nodes
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DBMS → Joins 1

Semi-join optimization in distributed queries sends
Only join-attribute projection to remote site to reduce data transfer
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