Basics .. But Important
Databases
Computer-based repositories for data
characteristics
Large amount of data (auxiliary memory)
Complex data organizations
Centered around data, not processes
Model real-world enterprises
Advantages of Databases
Data sharing
Privacy (authorization mechanism)
Decreased redundancy and increased consistency
Reliable storage of data (backup and recovery mechanisms)
Enforcement of standards
History
Integrated Data Store, first general-purpose DBMS, early 1960s, Charles Bachman, General Electrics
Information Management System (IMS), late 1960s, IBM
Relational database model, proposed in 1970, Edgar Codd, IBM’s San Jose Laboratory
Structured Query Language (SQL), standardized in the late 1980s
More powerful query languages, complex analysis of data, support for new data types (e.g., images), late 1980s and 1990s
Packages which come with powerful customizable application layers
Internet
Relational data model
Introduced in 1970 (Ted Codd)
Provided higher level of data independence than its predecessors (network and hierarchical models)
Easy to understand-high level abstractions
Slow to be adapted (80’s)-slow discovery of efficient algorithms
Relies on two concepts:
Mathematical relations
Have simple formalisms
Supported by a well understood set theory
Tables
Are commonly used in different contexts, and so intuitively understood
Background
SQL = Structured Query Language
Created in late 70’s at IBM, under the name of SEQUEL
Went through major standardizations (which contributed to its wide acceptance):
SQL-86 (SQL1)
Queries + some schema definitions & manipulation
SQL-89
Referential integrity SQL-92 (SQL2)
Revised and expanded
SQL-99 (SQL3)
Archive rules & triggers, recursive operations, aggregate operations, object-oriented features
Consists of
A Data Definition Language (DDL) for declaring database schemas
Data Manipulation Language (DML) for modifying and querying database instances

If you want to become a good developer or Designer , you should have a good grip on your related database and it's usage with you applcicaion....
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