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Ruby Length vs Size vs Count method

Ruby provides us three methods to interact with Array, Hashes or Objects.   Length Size Count   Lets takes a simple array to explain the difference between these methods   array1 = [A, B, C, D, E] &nbs...

What is the use of HAVING Clause in MySQL?

The HAVING clause is used with aggregate functions as the WHERE clause can not be used with them. HAVING Syntax SELECT column_name, aggregate_function(column_name) FROM table_name WHERE column_name operator value GROUP BY column_name HA...

What is the use of COUNT() function in MySQL?

In MySQL, COUNT() function used to return the number of rows that matches with a specified criteria. Syntax: COUNT(column_name) When we use COUNT(column_name) function in select query it returns the number of rows for the specified colum...

How to count unique values from table in mysql?

Sometimes we have the requirement to count how many unique values are in the table. We can do this by using "Distinct" and count(). SELECT COUNT(DISTINCT column_name) FROM table_name; Example: Suppose you have a table user from which you ...
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