MySql COUNT() function
Ref: w3resource MySQL Tutorial
MySQL Count function
MySQL COUNT() function returns a count of numberof non-NULL
values of a given expression.
If it does not find any matching row, it returns 0.
Here is the Syntax:
COUNT(expr);
We will see different types of usage of MySQL Count function in
a moment.
MySQL Count function
Table for demonstration:
MySQL Count function
To return the number of rows in author table:
SELECT COUNT(*) FROM author;
MySQL COUNT() with logical operator:
SELECT country,pub_city,COUNT(*) FROM publisher WHERE
country='USA' OR country='UK' GROUP BY country,pub_city;
MySQL Count function
MySQL COUNT() using multiple tables:
Table book_mast
MySQL Count function
MySQL COUNT() using multiple tables:
Table book_mast
MySQL Count function
SELECT publisher.pub_name,COUNT(*)FROM publisher,book_mastWHERE
publisher.pub_id=book_mast.pub_idGROUP BY publisher.pub_id;
MySQL COUNT() function with GROUP BY
SELECT country,COUNT(*)FROM author GROUP BY country;
MySQL COUNT() function with group by on multiple columns
SELECT country,pub_city,COUNT(*)FROM publisher GROUP BY
country,pub_city;
MySQL Count function
SELECT cate_id,COUNT(DISTINCT(pub_lang)),
ROUND(AVG(no_page),2)FROM book_mastGROUP BY cate_id;
MySQL COUNT() function with distinct
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