TSQL - Logical OR and AND Operations in SQL Server

In SQL Server, logical operators are used to test for the truth of some condition. Based on the expressional conditions, they return a true or false value to combine one or more true or false values.

Logical Operator OR - If you are using logical operator OR that means any one or both conditions will be TRUE. In this case, if first condition is TRUE then second condition will also checked it which can be either TRUE or FALSE. 

Logical Operator AND - If you are using AND logical operator then both condition should be true for the results. We can say that if first condition is false then second condition will be checked also. 

When you are working some data queries then there are few chances to miss out simple logic order. If you are not writing your queries carefully then AND and OR statements can greatly change a data set. We can avoid common SQL bugs by either using parenthesis or organising our statements to represent the logic that should be applied. 

To understand these operators, we can take an example of customer data as given below-

CustId	CustName	CustEmail	CustAddress	CustMobile
101	Ryan Arjun	ryan.arjun@gmail.com	New Delhi, India	2541563214
102	Kimmy Wang	kwang@htc.com	New York, USA	4156321425
103	Bill Smith	bill.smith@google.com	Sydney, Australia	1562543214
104	Rose Gray	roseg@dell.com	British Columbia, Canada	5632125414
105	John Day	dayh@google.com	London, UK	4569870671

If we want to pull the data for customer where customer name like ‘Ryan%’ and Address like ‘%USA%’ or email like ‘%google%’ then how can we use these both logical operators (AND or OR) as given below-

----- Select statements SELECT [CustId]       ,[CustName]       ,[CustEmail]       ,[CustAddress]       ,[CustMobile]   FROM [dbo].[Tbl_Customer_Master]   ----- customer name  start with Ryan   where ([CustName] like 'Ryan%' ----- customer Address  like USA   AND [CustAddress] like '%USA%') ----- customer email with google   OR [CustEmail] like '%google%' ----- Output Result CustId CustName CustEmail CustAddress CustMobile 103 Bill Smith bill.smith@google.com Sydney, Australia 1562543214 105 John Day dayh@google.com London, UK 4569870671

Conclusion

Logical operators compare two conditions at a time to determine whether a row can be selected for the output. They can change the result output if you are not using them carefully.