SELECT WHERE — TutorialBrain

WHERE Clause

WHERE clause is used to filter the records based on certain conditions. In short, WHERE clause filters the number of rows returned by the Query

Suppose, I want to get the BusinessEntityId, NationalIdNumber, BirthDate and MaritalStatus where Employees are Single, then you can code –

SELECT BusinessEntityID, NationalIDNumber, BirthDate, MaritalStatus
FROM HumanResources.Employee
WHERE MaritalStatus = 'S';

Order Of execution in SQL

Note It is not mandatory that the column which participates in the ‘WHERE’ clause must be present in the SELECT statement.

Order in which SQL server will execute –

FROM -> WHERE -> SELECT

You can also have something like this –

SELECT BusinessEntityID, NationalIDNumber, BirthDate
FROM HumanResources.Employee
WHERE MaritalStatus = 'S';

This time, I want to know all the Employees whose BirthDate > ‘1985-01-20’, then you can code –

SELECT *
FROM HumanResources.Employee
WHERE BirthDate > '1985-01-20';

Note The WHERE clause is not only used in the SELECT statement, it is also used in the UPDATE, DELETE statement, etc.

We will master the UPDATE, INSERT, UPDATE and a lot of other SQL statements as we move further in this tutorial.

Similarly, if I ask you to get the BusinessEntityId, NationalIdNumber and Birth Date where Birth year is greater than 1985, then you can code like –

SELECT BusinessEntityID, NationalIDNumber, BirthDate
FROM HumanResources.Employee
WHERE year(BirthDate) > '1985';

Year() function is used to extract the year from a date. Like this, there are so many functions which we are going to master in this tutorial.

Till now, we have used = and > operators and in the same way, there are so many operators which can be used in the SELECT clause. You are going to master all those from the next article.

WHERE Clause

Order Of execution in SQL

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