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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