The SQL COUNT() function is a powerful and widely used feature to retrieve the number of records in a table. It simplifies tasks where manually counting entries would be tedious. Whether youโre working with a database of customers, products, or employees, COUNT() helps fetch accurate results efficiently.
For example, consider you have a table of registered voters in a city and need to count the total voters. Instead of manual counting, you can use SQLโs COUNT() function to achieve this instantly.
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Syntax of SQL COUNT Function
SELECT COUNT(column_name) FROM table_name;
In the syntax above:
Replace column_name with the name of the column you want to count.
Replace table_name with the name of your table.
Examples of SQL COUNT Function
Example 1: Counting Non-NULL Values in a Column
Consider a table named Vehicles with the following data:
Vehicle_Name
Vehicle_Type
Price
Tesla Model 3
Electric
45,000
Honda Civic
Sedan
NULL
Ford Mustang
Sports
60,000
Toyota Corolla
Sedan
25,000
Nissan Leaf
Electric
NULL
BMW X5
SUV
80,000
To count the total non-NULL Price values:
SELECT COUNT(Price) AS TotalPrices FROM Vehicles;
Output:
TotalPrices
4
Here, COUNT(Price) excludes the NULL values, so only four rows are counted.
Example 2: Counting Total Entries in a Table
Using the same Vehicles table, if you want to count all entries, regardless of whether Price is NULL or not:
SELECT COUNT(*) AS TotalVehicles FROM Vehicles;
Output:
TotalVehicles
6
The COUNT(*) function includes both NULL and non-NULL values.
SQL COUNT with the WHERE Clause
You can combine COUNT() with the WHERE clause to count rows meeting specific criteria.
Example 1: Counting Rows Based on Condition
From the Vehicles table, to count the number of electric vehicles:
SELECT COUNT(Vehicle_Name) AS ElectricVehicles FROM Vehicles WHERE Vehicle_Type = 'Electric';
Output:
ElectricVehicles
2
Example 2: Counting Based on Another Condition
Consider another table EmployeeRecords:
Emp_ID
Emp_Name
Salary
City
1001
Priya
60,000
Mumbai
1002
Amit
50,000
Delhi
1003
Ravi
70,000
Mumbai
1004
Sneha
40,000
Bangalore
1005
Arjun
60,000
Mumbai
To count employees based in Mumbai:
SELECT COUNT(Emp_Name) AS EmployeesInMumbai FROM EmployeeRecords WHERE City = 'Mumbai';
Output:
EmployeesInMumbai
3
SQL COUNT with DISTINCT
To count only unique values, use the DISTINCT keyword with COUNT().
Example: Counting Unique Cities
From the EmployeeRecords table, count the unique cities employees belong to:
SELECT COUNT(DISTINCT City) AS UniqueCities FROM EmployeeRecords;
Output:
UniqueCities
3
The three unique cities are Mumbai, Delhi, and Bangalore.
The SQL COUNT() function is a robust tool for handling data efficiently, offering the ability to count specific or all entries in a table. Its combination with clauses like WHERE and keywords like DISTINCT further enhances its capabilities.
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