COUNT() SQL FUNCTION

SQL COUNT() फ़ंक्शन के उदाहरण

COUNT(*) से पंक्तियों की संख्या गिनना

The table called products contains all the products a company sells. The COUNT(*) clause allows us to calculate the number of rows in the table. 

SELECT
    COUNT(*) AS number_of_rows
FROM productsसंचालित द्वारा

Counting unique values with COUNT(DISTINCT …)

The COUNT(DISTINCT column) syntax allows us to count the number of unique values in a column.

For example, each product has an associated brand in the products table. We can count the number of unique products and brands in the table.

SELECT
    COUNT(DISTINCT product_id) AS unique_product_count,
    COUNT(DISTINCT brand_id) AS unique_brand_count
FROM productsसंचालित द्वारा

Count rows that match a condition using COUNT() with CASE WHEN 

The COUNT(CASE WHEN condition THEN column END) syntax allows us to calculate the number of rows that match a condition.

For example, in the products table, each product has a list_price. We can calculate how many products are “expensive” (having a list price of more than $500) or otherwise.

SELECT
    COUNT(CASE WHEN list_price >= 500 THEN product_id END) AS expensive_product_count,
   COUNT(CASE WHEN list_price < 500 THEN product_id END) AS cheap_product_count
FROM productsसंचालित द्वारा

Count rows in groups using COUNT() with GROUP BY

COUNT() can be used with GROUP BY to find the number of rows in each group.

For example, the product table contains bicycle models from 2016 to 2019. To find the distribution of the bicycle, we can use COUNT(product_id) and GROUP BY model_year to count the number of products from each year. 

SELECT
    model_year,
    COUNT(product_id) AS product_count
FROM products
GROUP BY model_yearसंचालित द्वारा

Filter for groups using COUNT() with GROUP BY and HAVING

In example 4, we see that COUNT() can be used with GROUP BY. We can use the HAVING statement to filter for groups using the number of rows in that group.

For example, to find the number of years that have less than 50 products, we can use the following syntax. 

SELECT
   model_year
FROM products
GROUP BY model_year
HAVING COUNT(product_id) < 50संचालित द्वारा

Technical Requirements

COUNT() is a function that is available to all versions of modern SQL. DataCamp offers tailored courses to help you master SQL within the context of your chosen database system. Here are some options to get started. I would think Oracle would be the most different since it has some specific functions and additional features. 

• Creating PostgreSQL Databases course
• Introduction to SQL Server course
• Introduction to Oracle SQL course

Learn More about SQL

Keep learning SQL with DataCamp. I've written a few other tutorials to get you started. I hope you find them helpful.

• COALESCE() SQL Function
• FORMAT() SQL Function
• DATEDIFF() SQL Function

Also, consider our SQL Associate Certification, which I think looks great on your CV or resume.