Cover
Introduction
1. How to Retrieve Data From a Single Table
1.1. The Five Clauses of the SELECT Statement
1.2. Column Specifications
1.3. LIKE and REGEXP Operators
1.4. Arithmetic Operators
1.5. Column Aliases
1.6. Comparison Operators
1.7. IS NULL, BETWEEN, IN Operators
1.8. AND, OR, NOT Logical Operators
1.9. DISTINCT Clause
2. How to Retrieve Data from Multiple Tables
2.1. The JOIN Clause
2.2. Joining More Than Two Tables
2.3. The OUTER JOIN Clause
2.4. How to Code a UNION
3. Using Functions
3.1. Date Functions
3.2. Numeric Functions
3.3. String Functions
4. How to Insert, Update, Delete Data in Tables
4.1. The INSERT Clause With a Column List
4.2. The INSERT Clause Without a Column List
4.4. The UPDATE Clause With a Column List
4.4. The DELETE Clause
5. Summary Queries and Aggregate Functions
5.1. Aggregate Functions
5.2. Grouping Data
5.3. Simple GROUP BY Query
5.4. Improving the GROUP BY Query
5.5. Using the HAVING Clause
5.5. Using the HAVING and WHERE Clauses Together
5.6. COUNT(column_name) and COUNT(*)
5.7. Using the DISTINCT Statement
6. Working With Subqueries
6.1. The Subquery In a SELECT Statement
6.2. The Subquery in an UPDATE statement
6.3. Create a Duplicate Table From An Existing Table
6.4. The Subquery In a Delete Statement
7. SQL Views
7.1. SQL View Explained
7.2. Benefits of Using Views
7.3. Views That Allow UPDATE Statements
8. SQL Indexes
8.1. SQL Indexes Explained
8.2. Clustered vs. Non-clustered Indexes
8.3. Create an Index in Workbench Using an ERD
8.4. How to Manually Add an Index to an Existing Table
Glossary
Index
5.7

Using the DISTINCT Statement

Removing Duplicate Values With DISTINCT

  • The DISTINCT keyword allows you to eliminate duplicate rows in aggregate functions.
  • You may also use the DISTINCT keyword with columns of the base table in a SELECT statement.
  • COUNT(list_price) counts all the rows in the product table that have a list price.
  • COUNT(DISTINCT list_price) eliminates duplicate values in the list_price.

Code Sample:

Example
USE bike;
SELECT COUNT(list_price), COUNT(DISTINCT list_price) 
FROM product;

Output:

ag_07.png

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CC BY-NC-ND International 4.0: This work is released under a CC BY-NC-ND International 4.0 license, which means that you are free to do with it as you please as long as you (1) properly attribute it, (2) do not use it for commercial gain, and (3) do not create derivative works.

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