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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 34

Which is NOT a NoSQL database type
Relational table store
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MongoDB is an example of
Document store
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Redis is an example of
Key-value store (in-memory)
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Apache Cassandra is an example of
Wide-column (column-family) store
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Neo4j is an example of
Graph database
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BASE vs ACID: BASE stands for
Basically Available Soft-state Eventually consistent
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Which database property is BASE designed to relax compared to ACID
Strong Consistency for better availability and performance
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CAP theorem P stands for
Partition tolerance: system continues operating despite network partitions
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MongoDB vs MySQL: key structural difference
MongoDB: schema-less documents; MySQL: fixed-schema tables
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Which SQL command imports a SQL dump file in MySQL command line
mysql -u user -p database < dump.sql
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mysqldump command creates
A SQL dump file with CREATE TABLE and INSERT statements
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Which SQL shows all indexes on the questions table in MySQL
SHOW INDEX FROM questions
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CHECK TABLE questions in MySQL performs
Checks table for errors or corruption
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OPTIMIZE TABLE questions in MySQL
Defragments the table and updates statistics for better performance
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ANALYZE TABLE questions in MySQL
Analyzes and stores key distribution statistics for the optimizer
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MyISAM vs InnoDB: key difference
InnoDB supports transactions and FK; MyISAM does not (faster for read-heavy workloads)
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Row-level locking in InnoDB vs table-level locking in MyISAM
Row-level allows higher concurrency for writes; table-level blocks entire table
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Which MySQL data type stores IPv4 addresses efficiently
INT UNSIGNED (use INET_ATON/INET_NTOA for conversion)
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ENUM vs SET in MySQL: difference
ENUM: stores one value from list; SET: stores one or more values from list
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Which stores multiple selected values in one column
SET
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JSON column in MySQL 5.7+ allows
Binary JSON with validation and JSON path queries
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MySQL -> operator on JSON column
Extracts a JSON value: col->'$.key'
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MySQL ->> operator on JSON column
Extracts JSON value as unquoted string (JSON_UNQUOTE(JSON_EXTRACT(...)))
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Which MySQL function checks if JSON value contains a path
JSON_CONTAINS_PATH(json,'one','$.path')
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Generated/Computed column in MySQL is
A virtual or stored column whose value derived from an expression
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Which SQL creates a virtual generated column for full name
ALTER TABLE emp ADD full_name VARCHAR(100) AS (CONCAT(first_name,' ',last_name)) VIRTUAL
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Common Table Expression (CTE) scope
Only within the single query that defines it
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SQL:2003 MERGE statement equivalent in MySQL
INSERT ... ON DUPLICATE KEY UPDATE
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INSERT IGNORE in MySQL
Silently skips rows that would cause unique constraint violations
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REPLACE INTO in MySQL
Deletes existing row then inserts new one if PK/unique key conflicts
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Which SQL checks if a table exists before creating it
CREATE TABLE IF NOT EXISTS questions (...)
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Which MySQL function returns the last auto-increment ID inserted
LAST_INSERT_ID()
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PHP PDO lastInsertId() in Laravel context (DB::getPdo()->lastInsertId()) returns
The auto-increment ID of the last inserted row
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DB::table('questions')->insertGetId(['question'=>'Q?',...]) returns
The auto-increment ID of the newly inserted row
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DBMS → Transactions 4

Which MySQL engine supports ACID transactions
InnoDB
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Which Laravel method handles database transactions
DB::transaction(callback)
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DB::beginTransaction() followed by DB::commit() vs DB::rollBack()
beginTransaction starts explicit transaction; commit saves; rollBack undoes all changes
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Which Laravel method retries a transaction on deadlock
DB::transaction(callback,3) - second param is number of retry attempts
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DBMS → Joins 1

Lateral join (LATERAL keyword) allows
Subquery in FROM to reference columns from preceding FROM items in same query
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DBMS → DDL Commands 1

DROP TABLE IF EXISTS questions
Drops table only if it exists (no error if it doesn't exist)
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