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

240 Chapter 9 Creating Your Web Database
In practice, BLOB and TEXT columns are the same except that BLOB is case sensitive
and TEXT is not. Because these column types can hold large amounts of data, they
require some special considerations.We discuss this issue in Chapter 12.
The third group has two special types: SET and ENUM.The SET type specifies that values
in this column must come from a particular set of specified values. Column values
can contain more than one value from the set.You can have a maximum of 64 things in
the specified set.
ENUM is an enumeration. It is very similar to SET, except that columns of this type can
have only one of the specified values or NULL, and you can have a maximum of 65,535
things in the enumeration.
We summarized the string data types in Tables 9.9, 9.10, and 9.11.Table 9.9 shows the
plain string types.
Table 9.9 Regular String Types
Type Range Description
[NATIONAL] 0 to 255 Fixed-length string of length
CHAR(M) characters M, where M is between 0 and
[BINARY | ASCII | UNICODE]
255.The NATIONAL keyword
specifies that the default
character set should be used.
This is the default in MySQL
anyway, but is included because it
is part of the ANSI SQL standard.
The BINARY keyword specifies that
the data should be treated as case
sensitive. (The default is case
sensitive.) The ASCII keyword
specifies that the latin1 character
set will be used for this column.The
UNICODE keyword specifies that
the ucs character set will be used.
CHAR
Synonym for CHAR(1).
[NATIONAL] VARCHAR(M) 1 to 255 Same as above, except they are
[BINARY] characters variable length.
Table 9.10 shows the TEXT and BLOB types.The maximum length of a TEXT field in characters
is the maximum size in bytes of files that could be stored in that field.