Databases in PHP, SQL Basics

The Structured Query Language, SQL, which is commonly pronounced as if it was a
word – “seekul”, is used to access a database in a modern database management system (DBMS). Now, before we get into coding specific commands in PHP,
it is very worthwhile to get an overview of the basic elements of the language
and the purpose of those elements.

In SQL everything is done in a “query”.  Personally I think this must be
because somebody got the idea that since it’s a query language, everything must
be a query, and made it so even if it’s an instruction like “add this record”.

That would be an insert query!  Ah well, if I want to be a master of SQL I
will have to toe the line an accept the expanded notion of  “queries”! 
More about them later — first, lets take a look at the most common commands
you’ll see.

Create

It seems logical to begin with the create command, since it is used to create
databases and the tables within them.  In practice, databases are usually
created outside an application like a PHP program.  They are most
frequently created using a management tool of the DBMS.  For this reason,
you probably won’t write many database create commands.  It is also used to
create new tables, however.

Drop

The opposite of create, drop is used to delete databases and tables. 
For the same reasons stated for create, you’ll probably write more table drops
than database drops.

Insert

The first of the record level commands, insert is used to create a record in
a table.  Most of the work you do in database systems will involve
operations on records.  Remember that a record corresponds to a row in a
table (the columns are the data elements, or fields, within a record.)