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