T-SQL Basics – Day 1

ByHariharan Rajendran

T-SQL Basics – Day 1

If you are reading this article then you are looking an very easy way to understand the T-SQL Scripts.

Let us learn T-SQL with a scenario, consider you have a sheet with some employee information. Your boss asking questions from that sheet and you need to answer him. In simple, your task is “Read from Sheet”.

Convert the general words into technical terms,

Sheet – Table (Employee) in a Database

Questions – T-SQL Statement

Answer – Output of T-SQL

Read – Select

Read from Sheet – Select from Table

If you are familiar with above terms then you can easily learn T-SQL Statements.

Let’s start,

Boss: What are the information available of an employee?

You: Read all the field name from Sheet

Tab1

T-SQL: SELECT * FROM Employee

Tab17

Note: “*” denotes all the fields from a table.

Boss: Do we have employee Name, Age & Country?

You: Yes

Tab2

T-SQL: SELECT Name, Age, Country FROM Employee

Tab18

Boss: What is the age of Richard? Or what is the country name of Richard?

You: 42 or UK

Tab3

T-SQL: SELECT * FROM Employee Where Name=’Richard’

Tab13

Note: Need to use WHERE keyword when we say specific data.

Boss: Who are all crossed age 40?

You: Read from sheet

Tab4

T-SQL: SELECT * FROM Employee WHERE Age > 40

Tab14

Note: Need to use WHERE keyword when we say specific data.

Boss: Whose names start with letter K?

You: Read from sheet

Tab5

T-SQL: SELECT * FROM Employee WHERE Name LIKE ‘K_%’

Tab15

Note: Need to use WHERE keyword when we say specific data. Use LIKE keyword when you want to play with the letters or pattern in a value. There are few other patterns available for LIKE which will discuss in the next article.

Boss: Convert the values of a Marital Status column into detailed values.

You: Add a new column

Tab6

T-SQL: SELECT *, CASE WHEN [Marital Status] =’M’ THEN ‘Married’ ELSE ‘UnMarried’ End MStatus FROM Employee  

Tab16

Note: Use “CASE WHEN XXXX THEN XXXXX ELSE XXXXX END” Syntax when you want derive something. We can discuss the detailed version above syntax in next article.

 

About the Author

Hariharan Rajendran author

Hariharan Rajendran is a Microsoft Certified Trainer and Lead BI Solutions Consultant with 8+ years of experience in Database, BI and Azure platforms. Hariharan is also an active community leader, speaker & organizer and leads the Microsoft PUG (Power BI User Group – Chennai), SQLPASS Power BI Local Group – Chennai and an active speaker in SQL Server Chennai User Group and also a leader in Data Awareness Program worldwide events. Hariharan also frequently blogs (www.dataap.org/blog), provides virtual training (on ad-hoc basis) on Microsoft Azure, Database Administration, Power BI and database development to worldwide clients/audience.

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