SQL basics

Question 1

Database

Answer 1

-organized collection of data

Question 2

Relational Database

Answer 2

• link data in one table to related data in another table
• tables are like named spreadsheets that each track a single idea or type of record
• columns are the properties of each record (name, age, etc)
• each row is itself a record (values)

Question 3

SQL

Answer 3

Structured Query Language

• a standard for database languages
• managed by the American National Standards Institute
• it is easy to red by design
• you can

Question 4

Query

Answer 4

A single SQL statement

-statements are used to perform tasks or issue commands to an RDBMS – that is, a Relational Database Management System. For example, you can update data in, or retrieve information from, a table.

Question 5

SQL Sub-Languages

Answer 5

DDL
DML
TCL

Question 6

DDL : Data Definition Language

Answer 6

statements that define database structure

Question 7

DML : Data Manipulation Language

Answer 7

statements that manipulate table data

CRUD: Create, read, update, delete

Question 8

TCL : Transaction Control Language

Answer 8

statements that control the execution of queries

-transaction: a group of SQL statements executed together

Question 9

Columns in tables

Answer 9

-each column holds a single type of data

Question 10

Column data type

Answer 10

• varchar: text data of variable length
• integer: 32-bit, signed whole numbers
• smallint: 16-bit, signed whole numbers
• number (n,d): decimal numbers with limited significant figures
• float: floating point numbers
• date: a d/m/yyy record
• timestamp: a combination of a date and time

-for every data type you can have a null value which means the cell for a row is empty