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criteria you specify.
Let's go back to our example firstname and lastname table – let's say the
table was called 'names'. To get Bob Smith's name in there to begin with, we
would have used SQL that looked like this:
INSERT INTO names VALUES ('Bob', 'Smith');
The ID number would be assigned automatically be the database. Then, later
on, if we wanted to find out who customer 123 was, we could run this SQL:
SELECT * FROM names WHERE id = '123';
This would get us customer 123's record from the database – Bob Smith's
record.
SQL might look complicated, and it can be, but that complexity is helped by
the fact that there aren't very many SQL commands you're likely to ever
need. Really, most websites can get by with just these statements:
CREATE. Used to create new database tables. You have to tell the database
which fields (columns) you want, and what kind of data (text, dates, etc.)
each field is going to contain.
SELECT. This command is used to search tables. You can use operators like =
(equals), < (less than) and > (greater than) to find the record you're after. For
example, if you wanted to find all your sales this week, you would work out
the date a week ago and use SELECT * FROM sales WHERE date > – that is,
"find all records in the sales table where the date is greater than...".
INSERT. Lets you add new records to the table.
UPDATE. Once you've inserted data, update lets you modify parts of it.
Useful if, for example, Bob Smith tells you he'd prefer to be known as Robert
Smith. Update lets you change the data without having to delete and
re-insert it, which means that records get to keep their existing ID nun
DELETE. Removes existing rows from the table, using the same basic syntax
as SELECT.
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