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DBMS Basics
Database
: Organized collection of data.
DBMS
: Software for managing databases with CRUD operations.
Database System
= Database + DBMS.
Storage Engine
: Manages how data is stored on disk.
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Operations
Read
: Load data from DB into memory.
Write
: Save changes from buffer to DB.
Subquery
: Nested query inside another.
Correlated Subquery
: Executes per row of the outer query.
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Languages in DBMS
Type
Purpose
Examples
DDL
Define structure
CREATE
,
DROP
,
ALTER
DML
Manipulate data
SELECT
,
INSERT
,
UPDATE
DCL (control)
Permissions
GRANT
,
REVOKE
TCL
Transactions
COMMIT
,
ROLLBACK
,
SAVEPOINT
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Database Design
Conceptual
: Entity, relationships, constraints.
Logical
: Map conceptual to DB structure.
Physical
: Storage, indexing, optimization.
Data Independence
: Design and storage layers are decoupled.
Transparent DBMS
: hides its physical structure to focus on logical design
Database partitioning:
process of dividing a logical database into independent components for horizontal scaling & faster access to specific portions
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Data Abstraction Levels