Practice 02 sql basics

Understanding SQL Datatypes Numeric Exact numeric data types ● With fixed precision and scale, there are more data types: ​decimal and numeric.. s ​ scale The number of decimal digits

Practice 02 SQL Basics

Outline

I Creating your first table

Naming conventions

The above tables does not have naming convention

===>

The above tables have naming convention

Understanding schemas

While a database is the primary container of all objects, schemas offer another level of

containment and organization within a database

Using a schema, a user can group objects of similar scope or ownership together By default, the database owner (dbo) schema is automatically created within a database Any object that is created is added to this schema

Understanding SQL Datatypes

Numeric

Exact numeric data types

● With fixed precision and scale, there are more data types: ​decimal and numeric

decimal[ ( ​p​[ ,​s​] )] and numeric[ (​p​[ ,​s​] )]

p (precision)

The maximum total number of decimal digits that will be stored, both to the left and to the right of the decimal point The precision must be a value from 1 through the

maximum precision of 38 The default precision is 18

s ​ (scale)

The number of decimal digits that will be stored to the right of the decimal point This number is subtracted from ​p​ to determine the maximum number of digits to the left of

the decimal point Scale must be a value from 0 through ​p​ Scale can be specified only

if precision is specified The default scale is 0; therefore, 0 <= ​s​ <= ​p​

Example: decimal(4,2): To store a four-digit number with only two digits to the right of the decimal place

Approximate numeric data types

● Approximate-number data types for use with floating point numeric data Floating point data is approximate; therefore, not all values in the data type range can be represented exactly The ISO synonym for real is float(24)

float [ ( ​n​) ] Where ​n​ is the number of bits that are used to store the mantissa of the float

number in scientific notation and, therefore, dictates the precision and storage size If ​n

is specified, it must be a value between 1 and 53 The default value of ​n​ is 53.

STRING

Date and time data types

Understanding column properties

● Allow null

● Primary key

● Length

● Unique

● Identity

Creating tables

Do it yourself with Employee table

Employee(EmployeeID, Firstname, MiddleName, LastName)

EmployeeID: int, not null, identity (1,1)

Firstname: varchar, 50, Not null

MiddleName varchar, 50, null

Lastname, varchar, 50, not null

Altering table

❏ Add one more column Gender to Employee table

Understanding computed columns

❏ Add one more column Fullname = FirstName + ‘, ‘ + LastName to Employee table

Adding constraints to a table

Primary key constraints

Default constraints

Unique constraints

Check constraints

❏ Set EmployeeID property as primary key

❏ Set Default value (1) for Active property

❏ Set SocialSecurityNumber property as Unique value

❏ Create check constraint Gender = Female or Male

Foreign key constraints

❏ Creating foreign key constraint between Address table and Employee table, namely, between EmployeeID on Address table to EmployeeID on Employee table

Create DB diagram

Practice with the HR database

SQL ​​: ​ https://www.w3resource.com/sql-exercises/sorting-and-filtering-hr/index.php

1 Write a query in SQL to display the full name (first and last name), and salary for those employees who earn below 6000

2 Write a query in SQL to display the first and last_name, department number and salary for those employees who earn more than 8000

3 Write a query in SQL to display the first and last name, and department number for all employees whose last name is “McEwen”

4 Write a query in SQL to display all the information for all employees without any department number

5 Write a query in SQL to display all the information about the department Marketing

Homework

https://en.wikibooks.org/wiki/SQL_Exercises/The_Hospital

https://www.w3resource.com/sql-exercises/hospital-database-exercise/sql-exerci se-on-hospital-database.php