Summary of "SQL - SELECT DISTINCT Statement - W3Schools.com"

The video titled "SQL - SELECT DISTINCT Statement" from W3Schools.com explains the purpose and usage of the SQL SELECT DISTINCT Statement, which is used to retrieve unique values from a database table.

Main Ideas and Concepts:

Purpose of SELECT DISTINCT: The SELECT DISTINCT statement is used to filter out duplicate entries in a dataset, allowing users to see only unique values.
Example Context: The video uses a 'Customers' table with a 'Country' column to illustrate how SELECT DISTINCT works, showing that multiple entries from the same Country can be condensed into a list of unique Country names.
Syntax: The basic syntax is presented as:
- SELECT DISTINCT column_name
- In the example, it would be SELECT DISTINCT Country.
Output Comparison: Without the DISTINCT keyword, every Country would be listed for each customer, but with DISTINCT, only unique Country names are shown.
Counting Distinct Values: The video introduces the COUNT function in conjunction with DISTINCT:
- COUNT(DISTINCT column_name) is used to COUNT the number of unique entries in a column.
- A note is made that MS Access does not support COUNT with DISTINCT, but a subquery can be used as a workaround.

Methodology/Instructions:

Identify the column from which you want unique values (e.g., 'Country').
Write the SQL query using the syntax:
```
SELECT DISTINCT column_name
```
To COUNT unique values, use:
```
COUNT(DISTINCT column_name)
```
If using MS Access, implement a subquery to achieve similar results.

Conclusion:

The video emphasizes the utility of the SELECT DISTINCT statement for data analysis and encourages viewers to practice using it in an interactive SQL editor provided by W3Schools.