To discover how many unique values there are in a particular column of your database, use the COUNT(DISTINCT) function in SQL. This function takes a single argument, which is the column you want to count the distinct values of. For example, if you wanted to count the distinct values in the name column of your database, you would use the following query:
Let's look at a few examples of how this function can be used. Suppose you have a table called users with the following data:
If you wanted to count the number of distinct names in this table, you would use the following query:
This query would return the result 3, since there are three distinct names in the table (John, Jane, and Bob).
How to Not Show Duplicates in SQL
If you want to not show duplicates in your SQL query, you can use the DISTINCT keyword. This keyword will return only the distinct (unique) values in the specified column. For example, if you wanted to get a list of all the distinct names in the users table, you would use the following query:
This query would return the result John, Jane, Bob, since those are the three distinct names in the table.
The COUNT(DISTINCT) and DISTINCT functions are supported by most major databases, including MySQL, PostgreSQL, and SQL Server. However, the syntax may vary slightly depending on the database you are using. For more information, check out the documentation for your particular database.