An introduction to SQL standard language for beginners and non-technical information people. Mostly covers SELECT statement using standard clauses, Joins, Sub-Queries and ...

1. Introduction toSQL
Ref: https://www.w3schools.com/sql/default.asp

2. What isSQL?
 SQL stands for Structured Query Language
 SQL lets you access and manipulate databases
 SQL is anANSI (American National Standards Institute) standard

3. WhatCanSQL
do?
 SQL can execute queries against a database
 SQL can retrieve data from a database
 SQL can insert records in a database
 SQL can update records in a database
 SQL can delete records from a database
 SQL can create new databases
 SQL can create new tables in a database
 SQL can create stored procedures in a database
 SQL can create views in a database
 SQL can set permissions on tables, procedures, and views

4. SQL is a
Standard -
BUT....
 There are different versions of the SQL language
 They all support at least the major commands
 Note: Most of the SQL database programs also have their own
proprietary extensions in addition to the SQL standard!

5. What is
RDBMS?
 RDBMS stands for Relational Database Management System.
 RDBMS is the basis for SQL, and for all modern database systems
such as MS SQL Server, IBM DB2, Oracle, MySQL, and Microsoft
Access.
 The data in RDBMS is stored in database objects called tables. A
table is a collection of related data entries and it consists of
columns and rows.
 Look at the "Customers" table:
SELECT * FROM Customers;

6. SQLSyntax
 DatabaseTables
Columns or Fields, Rows or Records, Indexes, etc…
 SQL Statements
SELECT * FROM Customers;
It’s not Case Sensitive
 SQL Expressions
Column Names, Formula, Sub-Query, etc…
 Semicolon after SQL Statements?
Some database systems require a semicolon at the end of each SQL statement
 Some ofThe Most Important SQLCommands
 SELECT - extracts data from a database
 UPDATE - updates data in a database
 DELETE - deletes data from a database
 INSERT INTO - inserts new data into a database

7. SQLSELECT
Statement
The SELECT statement is used to select data from a database

8. SELECT
Syntax
SELECT column1, column2, ...
FROM table_name;
SELECT *
FROM table_name;
SELECT CustomerKey, FirstName, LastName
FROM DimCustomer;

9. MoreSELECT
Stuff
 TOP N
 ORDER BY
 ORDER BY DESC
 DISTINCT
 Alias Names
 Concatenation

10. SELECT
WHERE
SELECT column1, column2, ...
FROM table_name
WHERE condition;
SELECT *
FROM DimCustomer
WHERE Gender = ‘F’;
Operator Description
= Equal
<> Not equal. Note: In some versions of SQL this operator may be written as !=
> Greater than
< Less than
>= Greater than or equal
<= Less than or equal
BETWEEN Between an inclusive range
LIKE Search for a pattern
IN To specify multiple possible values for a column

11. MoreWHERE
Stuff
 Dealing with NULL values
 AND, OR, NOT
 LIKE
 %
 _
 IN

12. SELECT
WHERE
Quiz
 Female Customers
 Female Customers younger than 40
 Female Customers younger than 40 and married
 MaleCustomers with middle name
 MaleCustomers who their names start with ‘Jon’
 Customers with income between 30000-50000
 Single female customers between 25-40 years old how make more
than $100K a year

13. Aggregation
 MIN
 MAX
 AVG
 COUNT
 SUM
 COUNT(DISTINCT)

14. GROUP BY  After WHERE Clause
 Before Order By Clause
 HAVING Clause
 Aggregations in GROUP BY
SELECT column1, column2, ...
FROM table_name
WHERE condition
GROUP BY column1, column2, ...;

15. GROUP BY
Quiz
 Customers by Gender
 Customers by Marital Status
 Customers by Age
 Customer Count by Gender
 Customer Count by Gender and Marital Status
 Average Income by Gender
 Female Customers count in 25-40 years old by Age
 …

16. SQLJOINs
 When do we join?
 Different types of JOINs
 CROSS JOIN
 How to choose which type is appropriate?
 Deal with NULL values

17. INNER JOIN
SELECT DimCustomer.CustomerKey, DimCustomer.FirstName,
DimCustomer.LastName,
DimGeography.EnglishCountryRegionName, DimGeography.City
FROM DimCustomer INNER JOIN
DimGeography ON DimCustomer.GeographyKey =
DimGeography.GeographyKey
SELECT DimGeography.EnglishCountryRegionName,
DimGeography.City, Customer.CustomerKey,
Customer.FirstName, Customer.LastName,
Sales.SalesOrderNumber, Sales.SalesAmount
FROM FactInternetSales Sales INNER JOIN
DimCustomer Customer ON Customer.CustomerKey =
Sales.CustomerKey INNER JOIN
DimGeography ON Customer.GeographyKey =
DimGeography.GeographyKey

18. LEFT/RIGHT
JOIN
SELECT P.EnglishProductName, PSC.EnglishProductSubcategoryName
FROM DimProductSubcategory PSC LEFT OUTER JOIN
DimProduct P ON P.ProductSubcategoryKey = PSC.ProductSubcategoryKey
SELECT P.EnglishProductName, PSC.EnglishProductSubcategoryName
FROM DimProductSubcategory PSC RIGHT OUTER JOIN
DimProduct P ON P.ProductSubcategoryKey = PSC.ProductSubcategoryKey

19. FULLJOIN
SELECT *
FROM DimProductCategory PC FULL OUTER JOIN
DimProductMarginTarget PCT ON PC.ProductCategoryKey =
PCT.ProductCategoryKey

20. SQLJOINs
Quiz
 Join DimProduct, DimProductSubcategory, DimProductCategory and
select Keys and Names from each table
 Join FactInternetSales, DimCustomer, DimProduct and show which
Product is Sold toWhich Customer with all the measures
 ProductCount by Category
 SalesAmount By Country
 OrderQuantity by Product Color
 SalesAmount and OrderQuantity byYear, Country, ProductCategory
 How many Bikes have we sold to each Country in 1386
 SalesAmount by Customer Gender
 SalesAmount by Customer Gender, MaritalStatus in the US
 Which one bought more Accessories, Men orWomen?

21. Sub-Queries
 Select Statements within Select Statement
 Used in:
 SELECT Clause
 FROM Clause
 JOINs
 WHERE Clause

22. Sub-Queries in
SELECT
 One row, One column
 Relates to the main query by usingWHERE
 Needs an Alias Name
 Could use internal joins as many times as needed
SELECT P.ProductKey, P.EnglishProductName, (
SELECT SUM(S.OrderQuantity) FROM FactInternetSales S WHERE
S.ProductKey = P.ProductKey
) AS SalesQuantity
FROM DimProduct P

23. Sub-Queries in
FROM
 Multiple rows, Multiple columns
 Treated just like aTable
 Needs an Alias Name
 Could use internal joins as many times as needed
SELECT MonthlySales.Year, Sum(TotalSales) ASTotalSalesSummary,
Min(TotalSales) ASTotalSalesMinimum, Max(TotalSales) AS
TotalSalesMaximum, Avg(TotalSales) ASTotalSalesAvg
FROM (
SELECT D.Year, D.MonthKey, Sum(OrderQuantity) ASTotalSales
FROM FactInternetSales S INNER JOIN
DimDatePersian D ON S.OrderDateKey = D.DateKey
Group By D.Year, D.MonthKey
) MonthlySales
Group By MonthlySales.Year

24. Sub-Queries in
JOINs
 Same as FROM Sub-Queries
 Relate to each other with JOIN
SELECT PRODUCTS.ProductCategoryKey,
PRODUCTS.EnglishProductCategoryName, SUM(OrderQuantity) AS
TotalSales
FROM FactInternetSales S INNER JOIN
(
SELECT PC.ProductCategoryKey, PC.EnglishProductCategoryName,
P.ProductKey
FROM DimProduct P INNER JOIN
DimProductSubCategory PSC ON P.ProductSubcategoryKey =
PSC.ProductSubcategoryKey INNER JOIN
DimProductCategory PC ON PC.ProductCategoryKey =
PSC.ProductCategoryKey
) PRODUCTS ON PRODUCTS.ProductKey = S.ProductKey
GROUP BY PRODUCTS.ProductCategoryKey,
PRODUCTS.EnglishProductCategoryName

25. Sub-Queries in
FROM
 Multiple rows, One column
 Usually used for IN or NOT IN conditions
 Doesn’t need an Alias Name
 Could use internal joins as many times as needed
SELECT *
FROM FactInternetSales
WHERE ProductKey IN (
SELECT P.ProductKey
FROM DimProduct P INNER JOIN
DimProductSubCategory PSC ON P.ProductSubcategoryKey =
PSC.ProductSubcategoryKey INNER JOIN
DimProductCategory PC ON PC.ProductCategoryKey =
PSC.ProductCategoryKey
WHERE PC.ProductCategoryKey = 1
)

26. CROSSJOIN
 Cartesian product of theTables involved in the JOIN
 Result rows count =Table1.Rows xTable2.Rows x …
 Used for computing Measures from unrelated Dimensions
 If aWHERE clause is added, the cross join behaves as an inner join
SELECT CUSTOMERS.CustomerKey, PRODUCTS.ProductKey,
(
SELECT ISNULL(SUM(S.OrderQuantity), 0) FROM FactInternetSales S
WHERE S.ProductKey = PRODUCTS.ProductKey and S.CustomerKey =
CUSTOMERS.CustomerKey
)TotalSales
FROM (
SELECT TOP(10) CustomerKey FROM DimCustomer
) CUSTOMERS CROSS JOIN
(
SELECT TOP(10) ProductKey FROM DimProduct ORDER BY ListPrice DESC
) PRODUCTS
ORDER BYTotalSales DESC

27. Sub-Queries
Quiz
 Select Customers withTotal Purchased Amount
 Select only the Products which have been sold
 Find out OrderQuantity sold in each country from each product
color
 Show monthly SalesAmount distribution in each country
 CombineYears and Customer Gender, and find each combination
Sales
 Yearly Sales for Customers in the US (Use Sub-Query not JOIN)

28. About Me
Amin Choroomi
CTO & Co-Founder at vdash
Software Developer, Teacher and Consultant
DataVisualization, Analytics, Dashboards
Data Warehousing, Integration, Business Intelligence
http://www.vdash.ir
choroomi@live.com
choroomi@vdashonline.com
https://linkedin.com/in/choroomi
@aminchoroomi

29. ThankYou