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    Tuesday, 17 December 2019

    SQL Aggregate Functions


    SQL Aggregate Functions

    An aggregate function allows you to perform a calculation on a set of values to return a single scalar value. We often use aggregate functions with the GROUP BY and HAVING clauses of the SELECT statement.

    The following are the most commonly used SQL aggregate functions:
    1. AVG – calculates the average of a set of values.
    2. COUNT – counts rows in a specified table or view.
    3. MIN – gets the minimum value in a set of values.
    4. MAX – gets the maximum value in a set of values.
    5. SUM – calculates the sum of values.
    All aggregate functions above ignore NULL values except for the COUNT function.

    AVG function
    The AVG function is used to calculate the average value of the numeric type. AVG function returns the average of all non-Null values.
    Syntax:
    AVG (expression)  
    Example:
    SELECT AVG(COST)  FROM PRODUCT; 

    COUNT function
    COUNT function is used to Count the number of rows in a database table. It can work on both numeric and non-numeric data types.
    COUNT function uses the COUNT(*) that returns the count of all the rows in a specified table. COUNT(*) considers duplicate and Null.
    Syntax:
    COUNT(*) 
    or 
    COUNT( expression ) 
    Example:
    SELECT COUNT(*)  FROM PRODUCT;  

    MIN Function
    MIN function is used to find the minimum value of a certain column. This function determines the smallest value of all selected values of a column.
    Syntax:
    MIN( expression ) 
    Example:
    SELECT MIN(RATE) FROM PRODUCT; 

    MAX Function
    MAX function is used to find the maximum value of a certain column. This function determines the largest value of all selected values of a column.
    Syntax:
    MAX( expression )  
    Example:
    SELECT MAX(RATE) FROM PRODUCT;  

    SUM Function
    Sum function is used to calculate the sum of all selected columns. It works on numeric fields only.
    Syntax
    SUM( expression )  
    Example:
    SELECT SUM(COST) FROM PRODUCT;  

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