SQL Exercises: Find number of customers have listed their names
SQL Aggregate Functions: Exercise-4 with Solution
From the following table, write a SQL query to count the number of customers. Return number of customers.
Sample table: customer
Sample Solution:
SELECT COUNT(*)
FROM customer;
Output of the Query:
count 8
Code Explanation:
The said SQL query that retrieve the total number of rows in the 'customer' table. The "SELECT COUNT(*)" statement specifies that the number of rows in the table should be counted. The "(*)" is a wildcard that counts all rows, regardless of the specific columns and their values.
The result of this query will be a single value that represents the total number of rows in the 'customer' table.
Relational Algebra Expression:

Relational Algebra Tree:

Explanation:
Visual presentation:

Practice Online
Query Visualization:
Duration:

Rows:

Cost:

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Previous SQL Exercise:Find the number of salesmen for each customer.
Next SQL Exercise: How many customers get a grade for their performance.
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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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