SQL Aggregate Function

Introduction

Aggregate functions perform calculations on a set of values and return a single value. With the exception of the COUNT aggregate function, all other aggregate functions ignore NULL Values.

Aggregate functions are frequently used with the GROUP BY clause of the SELECT Statement.

List of Aggregate Functions

1. AVG
2. CHECKSUM_AGG
3. COUNT
4. COUNT_BIG
5. MAX
6. MIN
7. SUM
8. STDEV
9. STDEVP
10. VAR
11. VARP

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Explaining the above functions:

1. AVG: Return the average of the values. The expression contains numeric value.
   
   
   
   
2. CHECKSUM_AGG: Return the checksum of the values in group. Null Values are ignored,
   
   
   
   
3. COUNT: Returns row count and int data type value always. It can be followed by Over clause.
   
   
   
   
4. COUNT_BIG: Count_big work in the same way as Count function but difference is that count_big return big int data type values. 
   
   
   
   
5. MAX: Return maximum value in expression. It ignores Null Values and can be followed by over clause.
   
   
   
   
6. Min: Return minimum values in expression and ignores Null values. 
   
   
   
   
7. SUM: Return sum of all the values, or only the distinct values.
   
   
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9. STDEV: Return the statistical standard deviation of all values in specified expression. It ignores null values.
   
   
   
   
10. STDEVP: Return the statistical standard deviation for the population for all values in specified expression. It ignores Null Values.
    
    
    
    
11. VAR: Return the statistical variance of all variables in specified expression. It ignores Null Values .
    
    
    
    
12. VARP: Return statistical Variance for the population for all values in specified expression. It ignores Null Values.
    
    

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