In SQL, the DISTINCT keyword is used in the SELECT statement to retrieve unique values from a database table. Any value that has a duplicate will only show up once.
"table_name" is the name of the table where data is stored, and "column_name" is the name of the column containing the data to be retrieved.
The examples will use the following table:
Table Store_Information
To select all distinct stores in Table Store_Information, we key in,
Result:
| Store_Name |
|---|
| Los Angeles |
| San Diego |
| Boston |
We can apply DISTINCT to multiple columns. If we want to get a list showing all unique combinations of stores and transaction dates, we would type in the following,
Result:
| Store_Name | Txn_Date |
|---|---|
| Los Angeles | Jan-05-1999 |
| San Diego | Jan-07-1999 |
| Los Angeles | Jan-08-1999 |
| Boston | Jan-08-1999 |
For these exercises, assume we have a table called Users with the following data:
Table Users
1. Which of the following SQL statement is valid?
a) SELECT DISTINCT * FROM Users;
b) SELECT DISTINCT First_Name FROM Users;
c) SELECT DISTINCT First_Name Last_Name FROM Users;
2. What's the result of the following query?
SELECT DISTINCT Join_Date From Users;
3. What's the result of the following query?
SELECT DISTINCT Gender, Join_Date From Users;
1. b)
2. The result is:
3. The result is:
Our website is made possible by displaying ads to our visitors. Please supporting us by whitelisting our website.