﻿ SQL: How many customers get a grade for their performance

# SQL Exercises: How many customers get a grade for their performance

## SQL Aggregate Functions: Exercise-5 with Solution

From the following table, write a SQL query to determine the number of customers who received at least one grade for their activity.

Sample table: customer

Sample Solution:

``````SELECT COUNT (ALL grade)
FROM customer;
``````

Output of the Query:

```count
7
```

Code Explanation:

The said SQL statement is used to count the total number of grades present in the 'customer' table. The "COUNT" function is used to count the number of non-null values in the specified column, in this case, the "grade" column.
The "ALL" keyword is not necessary as it is the default behavior for the "COUNT" function to count all values, including duplicates.

Explanation:

visual presentation:

## Query Visualization:

Duration:

Rows:

Cost:

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

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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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