![Topics to Cover in Lecture 2
◈ Text vs Numbers
◈ Comments in SQL: #, --, /*
◈ Not equal to sign
◈ Between command
◈ '[acs]%’ '[!acs]%’
◈ '[a-f]%](https://image.slidesharecdn.com/dmv-alllecturessql-240607073149-a8db1b5f/85/DMV-All-Lectures-SQL-pptxpComplete-SQL-24-320.jpg)
![SQL Functions
◈ TRIM([characters FROM ]string): removes leading spaces or the characters you specify. LTRIM, RTRIM.
◈ Window Functions:
◈ Over() to open a window: If no column is passed to over(), it is going create one window for all the
records, will iterate over all rows.
◈ Select *, max(salaray) over() as max_salary from employee: this will show max salary among all the
employees.](https://image.slidesharecdn.com/dmv-alllecturessql-240607073149-a8db1b5f/85/DMV-All-Lectures-SQL-pptxpComplete-SQL-38-320.jpg)
DMV - All Lectures SQL.pptxpComplete SQL
- 2. Course Expectations ◈ What do you expect from this course? ◈ Prior Exposure to SQL? ◈ My Experience with SQL.
- 3. Course Expectations SQL • Loading data • Writing queries • Knowing the terminology Excel • Becoming proficient with formulas and spreadsheet structuring • Learning other useful features PowerBI • Understand what makes a good visualization • Learn how to tell a story • Link dashboards to live data
- 5. Database ◈ USER DBMS DATABASE
- 6. SQL and Databases ◈ SQL is the language for generating, manipulating, and retrieving data from a relational database. ◈ Types?
- 7. ◈ Table, Tuples, Fields, Schema, Primary Key, Foreign Key ◈ Why not Excel? ◈ SQL (Sequel) Vs. MySQL
- 10. Creating Table and Databases
- 11. Data Types
- 13. Material to Cover ◈ Databases (Their control and administration) ◈ Select statement ◈ Selection of Database from toolbar or with command ◈ HR Data exploration: How do we start ◈ Entity Relationship Diagram (ERD) ◈ Relationship type: Many, One ◈ Joining Criteria ◈ Importing the HR tables: Countries and Customers ◈ Use of underscore instead of space
- 14. One to One: You and your ERP Many to One: You all studying from me One to Many: Me teaching you all Many to Many: Other students studying from same professor that you have studied from. Relationship of Customers to Country?
- 21. ERD Diagram ◈ A customer complains about an employee, how to find the data of the employee? ◈ Why not Country Name as PK and why Country ID?
- 22. Star Schema
- 23. Snowflake Schema
- 24. Topics to Cover in Lecture 2 ◈ Text vs Numbers ◈ Comments in SQL: #, --, /* ◈ Not equal to sign ◈ Between command ◈ '[acs]%’ '[!acs]%’ ◈ '[a-f]%
- 25. Topics to Cover in Lecture 3 ◈ Importing Date columns as text ◈ Color coding of SQL: Gray = Operator, Pink = Function ◈ YEAR, MONTH ◈ Temporary Table: INTO #hktemp, INTO ##hktemp ◈ Copying the data to Excel
- 26. Topics to Cover in Lecture 4 ◈ Refresher of Group By Function ◈ Distinct feature in Excel – Not Done ◈ Flow of Processing SQL commands ◈ ‘Having’ does not depend on Select statement ◈ Distinct feature in Excel ◈ Count Distinct *
- 27. Topics to Cover in Lecture 5 ◈ ORDER BY 2 or more columns ◈ ORDER BY on String
- 28. Inner Join
- 29. Left Join
- 30. Right Join
- 31. Full Outer Join
- 34. Null/Not Null
- 35. Null/Not Null ◈ Select * from customer where city is NULL; ◈ Is not same as ◈ Select * from customer where city = ‘NULL’; ◈ lets say id <> 2, then it won’t pull up the records with id = null. You have to specifically build that into condition that id <> 2 and id is null.
- 36. SQL Functions ◈ MODULUS or %: Checking the Remainder: ◈ select distinct city from station where ID%2 = 0; ◈ For Even: Either do MOD(ID, 2) = 0 or ID%2 = 0. ◈ For Odd: Either do MOD(ID, 2) = 0 or ID%2 = 1. ◈ POWER(X, 2): To raise x to the power (exponent) of 2.
- 37. SQL Functions
- 38. SQL Functions ◈ TRIM([characters FROM ]string): removes leading spaces or the characters you specify. LTRIM, RTRIM. ◈ Window Functions: ◈ Over() to open a window: If no column is passed to over(), it is going create one window for all the records, will iterate over all rows. ◈ Select *, max(salaray) over() as max_salary from employee: this will show max salary among all the employees.
- 39. SQL Functions ◈ ROW_NUMBER() to apply row numbers in a table. Specification in the Over() clause will tell us how to apply the row number. ◈ Example: ◈ Select a.CITY, a.CITY_LENGTH FROM ◈ (SELECT CITY, LENGTH(CITY) AS CITY_LENGTH, ◈ Row_number() over(order by LENGTH(CITY) asc, city asc) as short_length_rn, ◈ Row_number() over(order by LENGTH(CITY) desc, city asc) as long_length_rn ◈ FROM STATION) as a ◈ where a.short_length_rn = 1 or a.long_length_rn = 1 ◈ order by 1 asc;
- 40. SQL Functions ◈ DateAdd ◈ Datediff ◈ Left ◈ Right ◈ GetDate