SQL Count, Avg, Sum

SQL COUNT Function:

We are going to write an SQL query to count the number of rows in a table.  For is we will be making use of the count() function of SQL.

The SQL COUNT( ) function is used to return the number of rows in a table. It is used with the Select( ) statement.

If we have employee table with the following column emp_id, emp_name, emp_email, emp_contact_number  and we have to count the number of rows in  a table then we will do like this.

table_name : emmployee

column_name : salary

SYNTAX: 

SELECT COUNT(column_name) from table_name;

QUERY :

SELECT COUNT(salary) from employee

Note : We can use any of the column_name to count the number of rows in the table.

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SQL AVG Function:

We are going to see how to find the average value in a column in SQL.  A column in the SQL table is the vertical catalog structure.

Average of all values in a column

For this, we need to use avg() function. We have to pass the column name as a parameter. The avg() function has the following syntax:

SYNTAX:

SELECT AVG( column_name ) FROM table_name;

QUERY:

SELECT AVG( salary ) FROM employee;

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SQL SUM Function:

SELECT SUM is used to calculate the total value of an expression in SQL. It is the same as using the AGGREGATE function SUM ( ) in SQL.

In this article, we are going to see how to use “SELECT SUM” in SQL using suitable examples.

SYNTAX:

SELECT SUM(column_name) FROM table_name  WHERE condition;

QUERY:

SELECT SUM(salary) FROM employee WHERE salary > 50000;