CoverIntroduction1. How to Retrieve Data From a Single Table1.1. The Five Clauses of the SELECT Statement1.2. Column Specifications1.3. LIKE and REGEXP Operators1.4. Arithmetic Operators1.5. Column Aliases1.6. Comparison Operators1.7. IS NULL, BETWEEN, IN Operators1.8. AND, OR, NOT Logical Operators1.9. DISTINCT Clause2. How to Retrieve Data from Multiple Tables2.1. The JOIN Clause2.2. Joining More Than Two Tables2.3. The OUTER JOIN Clause2.4. How to Code a UNION3. Using Functions3.1. Date Functions3.2. Numeric Functions3.3. String Functions4. How to Insert, Update, Delete Data in Tables4.1. The INSERT Clause With a Column List4.2. The INSERT Clause Without a Column List4.4. The UPDATE Clause With a Column List4.4. The DELETE Clause5. Summary Queries and Aggregate Functions5.1. Aggregate Functions5.2. Grouping Data5.3. Simple GROUP BY Query5.4. Improving the GROUP BY Query5.5. Using the HAVING Clause5.5. Using the HAVING and WHERE Clauses Together5.6. COUNT(column_name) and COUNT(*)5.7. Using the DISTINCT Statement6. Working With Subqueries6.1. The Subquery In a SELECT Statement6.2. The Subquery in an UPDATE statement6.3. Create a Duplicate Table From An Existing Table 6.4. The Subquery In a Delete Statement7. SQL Views7.1. SQL View Explained7.2. Benefits of Using Views7.3. Views That Allow UPDATE Statements8. SQL Indexes8.1. SQL Indexes Explained8.2. Clustered vs. Non-clustered Indexes8.3. Create an Index in Workbench Using an ERD8.4. How to Manually Add an Index to an Existing TableGlossaryIndex
5.1

Aggregate Functions

Aggregate Functions

  • Aggregate functions are synonymous with column functions.
  • A summary query uses at least on column function.
  • AVG, SUM return numeric values.
  • MIN, MAX, COUNT can return numeric, date, or string values
  • All values are included in aggregate functions by default unless you specify the DISTINCT keyword
  • Duplicate rows are excluded in all aggregate functions with the exception of COUNT(*)
  • ***** IF YOU CODE AN AGGREGATE FUNCTION IN THE SELECT STATEMENT, YOU CANNOT ALSO INCLUDE NON-AGGREGATE FUNCTIONS IN THE SELECT STATEMENT UNLESS THOSE NON-AGGREGATE COLUMNS ARE INCLUDED IN A GROUP BY CLAUSE

Table 1. Aggregate Functions List

Aggregate Function

Output data-type

Result

AVG([DISTINCT] column_values)

numeric

The average of the non-null columns in the expression

SUM([DISTINCT] column_values)

numeric

The total of the non-null columns in the expression

MIN([DISTINCT] column_values)

numeric, date, string

The lowest value off the non-null columns in the expression

MAX([DISTINCT] column_values)

numeric, date, string

The highest value of the non-null columns in the expression

COUNT([DISTINCT] column_values)

numeric

The number of the non-null columns in the expression

COUNT(*)

numeric

The number of rows returned by the query

Code Sample:

USE bike;
SELECT AVG(list_price), SUM(list_price), MIN(list_price), 
    MAX(list_price), COUNT(list_price), COUNT(*)
FROM product;

Output:

ag_01.png

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