SQL- Introduction to Database

Posted 2021-02-08

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Introduction to Databases

1.     Database management system:

a.     Efficient, convenient, safe, multiuser storage & access to massive amounts of persistent data.

b.     Extremely prevalent in the world.

c.      WHY?

                                               i.     Massive-terabytes data, data handled by the systems are larger then memory of computing system.

                                             ii.     Persistent- different compared to computing since data not go away after program is done- multi-programs can run the same data.

                                            iii.     Safety-used for bank and business, needs to ensure data stays in a consistent state (not overwritten or lost when facing failures.)

                                            iv.     Multi-user-concurrently, consistent. -control at the level of data items instead of #of access.

                                              v.     Convenient-large amount of data. ???

physical data independence (the way data is laid out /stored is independent from the structure of data)- user app is immunity to changes in the data.

High level query languages ??? like human language, describe the purpose regardless algorithm to get data out (declarative).

                                            vi.     Efficient- performance is important- do complex queries/update per second

                                           vii.     Reliable- guarantee the system is made for specific app.

d.     Data app can be programed via frameworks, ex: Django, ruby.

e.      DBMS- used in conjunction (Middleware). Ex: web servers, app servers.

                                               i.     Benefit: help system interact with database

                                             ii.     Attention: some data intensive app may not use DBMS at all! (excel, Hadoop)

f.      Concepts:

                                               i.     Data Model:

1.     Describes how data is structured

2.     Relational do data model (most common) ??? data & data base are treated as a set of records

3.     XML: store data, it???s a document captures data.

4.     Graph: all data in the database is in the form of nodes and edges.

                                             ii.     Schema VS Data (Types VS Variables):

1.     Schema: sets up structure of database (GPA). Usually in the beginning.

2.     Data: actual data stored within the schema (ex. 4.0. 3.0???.)

                                            iii.     Data definition Language:

1.     Used to set up schema, start with high level design tools.

                                            iv.     DML (Data manipulation language): querying and modifying database.

g.     Key People involved:

                                               i.     DBMS Implementer: build system.

                                             ii.     Designer: establish schema, find the way how to structure data.

                                            iii.     Database application Developer: build app running on databases, interfacing between users and data

                                            iv.     Database Administrator: loads data, keep it running smoothly. Purpose: get the tuning parameters associates with the project correct. Highly valued