13 count avg sum function скачать в хорошем качестве

13 count avg sum function

Introduction to SQL aggregate functions Each query in SQL returns filtered results of groups of values and also the field values. SQL provides aggregate functions to help with the summary of large volumes of data. SQL aggregate function allows you to perform a calculation on a set of values to return a single numericalalue. We often use aggregate functions with the GROUP BY and HAVING clauses of the SELECT statement. All aggregate functions are deterministic. This means aggregate functions return the same value any time that they are called by using a specific set of input values. The following are the most commonly used SQL aggregate functions: AVG – calculates the average of a set of values. COUNT – counts rows in a specified table or view. MIN – gets the minimum value in a set of values. MAX – gets the maximum value in a set of values. SUM – calculates the sum of values. Notice that all aggregate functions above ignore NULL values except for the COUNT function. COUNT function example To get the number of the products in the products table, you use the COUNT function as follows: SELECT COUNT(admno) FROM stdtbl ; SQL AVG function calculates the average value of a column of numeric type. It returns the average of all non NULL values Example: To get the data the average of 'marks' from the 'markstbl' table, the following SQL statement can be used : SELECT AVG( marks ) FROM markstbl ;