ColdFusion 4.0 Primer
2. Changing Data
To modify existing data you must use the UPDATE statement.
UPDATE Friends SET Age = '21' WHERE Name like "Chris"
How this works is you first specify the table which you want to update, in our case "Friends", Then you pick the value using the SET keyword. If you wanted to update multiple values you would separate each by a comma, for instance SET Age = '21', FavMovie = 'The Patriot'. Finally we include the where clause, without it all rows would be updated. The UPDATE statement is very useful, for instance in our friends database we would use it to change someone's age when they have a birthday.
3. Deleting DataYou should always be very careful when deleting data. A slip of the mind or a typo and you could have an empty database.
DELETE FROM Friends WHERE Name = "Tim"
Lets say you had a falling out with a friend. You could delete their name from your friends database by using the above statement. Again the first thing specified is the table name followed by an optional WHERE statement. However remember that though the where statement is optional, without it everything in the table would be erased.
4. The Distinct Keyword
Sometimes when working with a database you do not want to return duplicate values. For instance when working with a Used Car database I wanted to dynamically generate a select form for vehicle make on the website. If I hadn't used the distinct keyword the select list would have been very long, it would have had 1 option for every car in the database. Using the distinct keyword in my SELECT statement limited the output to every distinct make within the database.
Select DISTINCT Make FROM Used
As you can see it looks just like a regular SELECT statement, just with the DISTINCT keyword thrown in to eliminate duplicate values.
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