Databases

What is a database?

A database is an organized collection of related data

What is a table in a database?

A table is a database object used to store records in a field in the form of columns and rows that holds data.

What is a record in a database?

A record (also called a row of data) is an ordered set of related data in a table.

What is a field in a database?

A field is an area within a record reserved for a specific piece of data. Examples: Employee Name, Employee ID, etc.

What is a data type?

Data type is the type of information the data is e.g. integer, date/time

What is a primary key?

A primary key is a field (or group of fields) that uniquely identifies a given entity in a table

What are the two types of databases?

Types of databases: ★ Flat-file ★ Relational

What is a flat-file database?

A flat-file database is a database in which all the data is stored in a single table

What is an advantage of a flat-file database?

Advantages of a flat-file database: ★ Simple to set up ★ Simple to understand

What is a foreign key?

A foreign key is: ★ A field that references the primary key of another table ✔︎ This creates a link between two tables

What is a relational database?

Relational databases are databases that: ★ Are made up of multiple tables ★ Made up of foreign keys and primary keys

Does a foreign key have to be unique?

No, a foreign key does not have to be unique

What are the advantages of relational databases?

Advantages of relational databases: ★ Data is only stored in one place and then referenced ➜ We input, update or delete a piece of data all in one place 𐬽 Prevents inconsistencies ★ Storing each piece of data once saves storage space ★ More secure — we can make some tables confidential so that only some users can access specific data ★ Data Independence - data can be changed without affecting the program you use to access it

What is the structure of an SQL query?

SELECT [fields are separated by commas e.g. name,gender]
FROM

How do you select everything from a table?

To select everything from a table, you can say: SELECT *

What does >= mean in SQL queries?

★ >= in SQL queries means (greater than or equal to) ★ Similar is true with <=

What two Boolean operators could we use to make WHERE searches more specific?

★ We can use the Boolean operators 'AND' and 'OR' to make WHERE searches more specific ★ e.g. WHERE rating >= 4 AND price_per_day <= 100

What does != mean in SQL queries?

!= means not equal to in SQL queries

How do you deal with string in SQL?

In SQL, you deal with string with "string"

How can you add complete records in tables?

INSERT INTO
VALUES(

How can you add incomplete records in tables?

INSERT INTO ()
VALUES(

How do you update values in a database?

UPDATE
SET = value, = other_value [etc.]
WHERE =

How do you delete values in a database?

DELETE
FROM
WHERE = condition [e.g. rating = 2.3, ID =7]

How do you reference field names in a relational database

In. Relational databases, you reference fields by saying:
★ .field [e.g. orders.drinks]

What line has to be added at the WHERE of relational databases?

Line has to be added to relational databases WHERE:
★ .primary_key1. = .primary_key2