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SQL Exercises: Find the number of salesmen for each customer

SQL Aggregate Functions: Exercise-3 with Solution

From the following table, write a SQL query that counts the number of unique salespeople. Return number of salespeople.

Sample table: orders


Sample Solution:

SELECT COUNT (DISTINCT salesman_id) 
FROM orders;

Output of the Query:

count
6

Code Explanation:

The given SQL query that retrieve the number of unique values in the "salesman_id" column from the 'orders' table. The "SELECT COUNT (DISTINCT salesman_id)" statement specifies that the number of unique values in the "salesman_id" column should be counted.
By using the keyword "DISTINCT", it is ensured that only unique values will be counted and duplicate values will not be added to the final result in any way.
The result of this query will be a single value that represents the number of unique values in the "salesman_id" column in the 'orders' table.

Relational Algebra Expression:

Relational Algebra Expression: Find the number of salesman currently listing for all of their customers.

Relational Algebra Tree:

Relational Algebra Tree: Find the number of salesman currently listing for all of their customers.

Explanation:

Syntax of find the number of salesman currently listing for all of their customers

visual presentation:

Find the number of salesman currently listing for all of their customers

Practice Online


Query Visualization:

Duration:

Query visualization of Find the number of salesman currently listing for all of their customers - Duration

Rows:

Query visualization of Find the number of salesman currently listing for all of their customers - Rows

Cost:

Query visualization of Find the number of salesman currently listing for all of their customers - Cost

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Previous SQL Exercise: Find the average purchase amount of all orders.
Next SQL Exercise: Find number of customers have listed their names.

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SQL: Tips of the Day

What is the best way to paginate results in SQL Server?

SELECT  *
FROM    ( SELECT    ROW_NUMBER() OVER ( ORDER BY OrderDate ) AS RowNum, *
          FROM      Orders
          WHERE     OrderDate >= '1980-01-01'
        ) AS RowConstrainedResult
WHERE   RowNum >= 1
    AND RowNum < 20
ORDER BY RowNum

Database: SQL Server

Ref: https://bit.ly/3MGrNlk

 





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