Week 1 Notes Flashcards
database and database system
organized collection of related information in a stored file // MS SQL Server, oracle, and access
field or attribute
column
record or tuple
row
relation // entity
a table // group of tables
metadata
data about data (table and column names, and data type included)
domain
range of values within a column (can encompass entire range or be restricted i.e. restricted to decimal digits 0-9, or regional like NE/NW/MW/SE/SW)
data validation rules
the enforcement of ‘uniqueness’ within data range
Entity Relationship Diagram (ERD)
commonly used to design and document a database
one- to-many relationship
a value that appears once as a primary key in table 1 appears (w same value) as foreign key in table 2. Denoted by infinity symbol, optional relationship
SQL
3rd generational language to access info in relational databases. Allows you to insert new rows, update info in existing rows, and delete rows. Allows you to up tables with their columns, data types, and constraints. Includes many functions and procedures to manipulate and format data.
SQL is non-procedural
how to access and select data is handles internally by SQL and is hidden from the user
query
question or instruction to retrieve data from tables// can be done by writing SQL statement or thru various graphical aids and templates in Enterprise manager or Query analyzer
A DBMS program can
access existing data, manipulate data to produce new data, generate a report, add/ update records, assign names, format, and establish relationships
an RDBMS integrates
raw data/ metadata for tables, indexes, etc and instructions for forms, reports, and queries into one file
null value indicates
value not assigned because it is unknown, not yet been recorded, or value for the column is not applicable
NOT A ZERO/ BLANK
primary key
one or more columns in a table with unique and not null values
data integrity
if two rows in a table are identical then table DOES NOT have DI
foreign key
one or more columns in a table with limited/ constrained values to the primary key it references. Can be null
the names of data types specify
a size (no of bits or bytes) and a structure/ arrangement to store the data.
data types are used when
creating tables, when a column is added to a table, when data is retrieved from RAM or disk
when specifying a data type
you are limiting the range of that data
