SQL

Question 1

What is SQL

Answer 1

Standard for managing data kept in relational database management systems

Question 2

What is MySQL

Answer 2

Open source relational database management system

Question 3

What are Joins?

Answer 3

Right, left, inner, and full joins combine rows from two or more tables

Question 4

Index

Answer 4

An index is a pointer to data contained within a table which allows for faster retrieval of records

Question 5

Constraints

Answer 5

Specify a rule for the data within a table limiting the type of data that can go within

Question 6

Type of Constraints

Answer 6

Primary key - identifies each record in a table
Not Null - used to prevent a Null value
Foreign Key - provides a unique identification of a row or record within another table
Default - automatically assigns a default value if there has not been a value already specified for a field
Check - used to verify that all values meet a specific criteria or condition in a field
Unique - ensures unique values are always inserted into a column
Index - used to create data and to obtain it from a database

Question 7

What are a Table and Field

Answer 7

Table: a collection of data that is organized into rows and columns
Columns are called fields and rows are records

Question 8

Data Control Language (DCL)

Answer 8

permits you to control access to the database

Question 9

Data Definition Language (DDL)

Answer 9

allows you to specify data structure in the database including deleting tables, creating them, or altering them

Question 10

Data Manipulation Language (DML)

Answer 10

allows you to manipulate data, update, insert, delete, or retrieve

Question 11

How to format SQL dates

Answer 11

Format function (SELECT FORMAT getDate(), ‘dd/MM/yyyy’)

Question 12

Primary Key

Answer 12

A primary key is used to ensure data in the specific column is unique and uniquely identifies a record in the relational database.

Question 13

Foreign Key

Answer 13

A foreign key is a column or group of columns in a relational database table that provides a link between data in two tables.
It refers to the field in a table which is the primary key of another table.

Question 14

What is Database denormalization

Answer 14

Is a method used to improve the performance of a database, allowing the retrieval of data in the quickest time possible.
Adds redundant database data into a table which in turn enables the performance of databases to improve, as the same data can be put in several places.

Question 15

Subquery

Answer 15

Subquery is a query nested inside a larger query