PHP and MySQL Web Development 4th Ed-tqw-_darksiderg

312 Chapter 13 Advanced MySQL Programming
Storage Engines
MySQL supports a number of different storage engines, sometimes also called table types.
This means that you have a choice about the underlying implementation of the tables.
Each table in your database can use a different storage engine, and you can easily convert
between them.
You can choose a table type when you create a table by using
CREATE TABLE table TYPE=type ....
The commonly available table types are
n MyISAM—This type is the default and what we have used so far in the book. It
is based on the traditional ISAM type, which stands for Indexed Sequential Access
Method, a standard method for storing records and files. MyISAM adds a number
of advantages over the ISAM type. Compared to the other storage engines,
MyISAM has the most tools for checking and repairing tables. MyISAM tables can
be compressed, and they support full text searching.They are not transaction safe
and do not support foreign keys.
n MEMORY (previously known as HEAP)—Tables of this type are stored in memory,
and their indexes are hashed.This makes MEMORY tables extremely fast, but,
in the event of a crash, your data will be lost.These characteristics make MEMO-
RY tables ideal for storing temporary or derived data.You should specify MAX_ROWS
in the CREATE TABLE statement; otherwise, these tables can hog all your memory.
Also, they cannot have BLOB, TEXT, or AUTO INCREMENT columns.
n MERGE—These tables allow you to treat a collection of MyISAM tables as a single
table for the purpose of querying.This way, you can work around maximum
file size limitations on some operating systems.
n ARCHIVE—These tables store large amounts of data but with a small footprint.
Tables of this type support only INSERT and SELECT queries, not DELETE, UPDATE,
or REPLACE. Additionally, indexes are not used.
n CSV—These tables are stored on the server in a single file containing commaseparated
values.The benefit of these types of tables only appears when you need
to view or otherwise work with the data in an external spreadsheet application
such as Microsoft Excel.
n InnoDB—These tables are transaction safe; that is, they provide COMMIT and ROLL-
BACK capabilities. InnoDB tables also support foreign keys.While slower than
MyISAM tables, the ability to use transactions in your applications is a worthy
trade-off.
In most web applications, you will generally use either MyISAM or InnoDB tables or a
mix of the two.
You should use MyISAM when you are using a large number of SELECTs or INSERTs
on a table (not both mixed together) because it is the fastest at doing this. For many web