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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

Relational Algebra Expression:

Relational Algebra Expression: Find number of customers have listed their names.

Relational Algebra Tree:

Relational Algebra Tree: Find number of customers have listed their names.

Explanation:

Syntax of find number of customers have listed their names

Pictorial presentation:

Find number of customers have listed their names

Practice Online


Query Visualization:

Duration:

Query visualization of Find number of customers have listed their names - Duration

Rows:

Query visualization of Find number of customers have listed their names - Rows

Cost:

Query visualization of Find number of customers have listed their names - Cost

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Previous:From the following table, write a SQL query to count the number of unique salespeople. Return number of salespeople.
Next: From the following table, write a SQL query to find the number of customers who got at least a gradation for his/her activity.

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SQL: Tips of the Day

SQL Server SELECT into existing table. 

INSERT INTO dbo.TABLETWO
SELECT col1, col2
  FROM dbo.TABLEONE
 WHERE col3 LIKE @search_key

This assumes there's only two columns in dbo.TABLETWO - you need to specify the columns otherwise:

INSERT INTO dbo.TABLETWO
  (col1, col2)
SELECT col1, col2
  FROM dbo.TABLEONE
 WHERE col3 LIKE @search_key

Database: SQL Server

Ref: https://bit.ly/3y6tpA3