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SQL Server WHERE

In this article, you will learn the use of the where a clause in SQL Server

Where clause is used to filter the records from data set when we query the table that time you will get the list of records, which are unnecessary when the application needs a specific set of records.

Syntax:

SELECT column_list
FROM table_name
WHERE search_condition;

In the above syntax, in where the clause, we filter the result set return from clause. Whereclause only filter the records when search condition to evaluate true. In where condition, we need to add logical expression.

where condition evaluates to TRUE,FALSE or UNKNOWN. The where clause won’t return any rows when search_condition evaluate falseor unknown

For the examples, we will use the below table

Searching records using single condtion

In the below example, will filter the records using employee id

SELECT *
FROM [Blog].[dbo].[Employee] where EmployeeID=1

Output:

Searching records using multiple condtion

In this example, we can filter records based on the <strong>Salary</strong> and <strong>JoinYear</strong> conditions along with AND and OR logical operators.

AND Condition

SELECT *
FROM [Blog].[dbo].[Employee] where Salary=10000 AND JoinYear=2018

Output:

OR Condition

SELECT *
FROM [Blog].[dbo].[Employee] where Salary=10000 OR JoinYear=2018

Output:

Filtering records using comparison operator

You can filter the records, using a comparison operator. I can demonstrate in the below example

SELECT *
FROM [Blog].[dbo].[Employee] where Salary>10000

We are filtering records greater than 10000.

Output:

Filtering records between two records

Using between clause, we can get the range between two values, now I need records between salary 10k and 25k.

SELECT *
FROM [Blog].[dbo].[Employee] 
where Salary between 10000  and 25000

Output:

Filtering records using List

Using the IN operator, we can filter result set using the multiple records in the search condition(1,5)

SELECT *
FROM [Blog].[dbo].[Employee] 
where EmployeeID in (1,5)

Output:

Filtering records contain a string

Using the wildcard operator like , we can get records containing a specific string, In the below example we are searching rows containing a character.

SELECT *
FROM [Blog].[dbo].[Employee] 
where [Employee Name] like '%a%'

Output:

Need help?

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