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

Choosing Column Data Types
239
Table 9.7
Continued
TIMESTAMP[(M)] 1970-01-01 A timestamp, useful for transaction reporting.
00:00:00 The display format depends on the value of M
(see Table 9.8, which follows).
Sometime The top of the range depends on the limit
in 2037
on Unix.
timestamps.
YEAR[(2|4)] 70–69 A year.You can specify two- or four-digit
(1970–2069) format. Each has a different range, as shown.
1901–2155
Table 9.8 shows the possible different display types for TIMESTAMP.
Table 9.8 TIMESTAMP Display Types
Type Specified Display
TIMESTAMP
YYYYMMDDHHMMSS
TIMESTAMP(14) YYYYMMDDHHMMSS
TIMESTAMP(12) YYMMDDHHMMSS
TIMESTAMP(10) YYMMDDHHMM
TIMESTAMP(8) YYYYMMDD
TIMESTAMP(6) YYMMDD
TIMESTAMP(4) YYMM
TIMESTAMP(2) YY
String Types
String types fall into three groups. First, there are plain old strings—that is, short pieces
of text.These are the CHAR (fixed-length character) and VARCHAR (variable-length character)
types.You can specify the width of each. Columns of type CHAR are padded with
spaces to the maximum width regardless of the size of the data, whereas VARCHAR
columns vary in width with the data. (Note that MySQL strips the trailing spaces from
CHARs when they are retrieved and from VARCHARs when they are stored.) There is a space
versus speed trade-off with these two types, which we discuss in more detail in
Chapter 12.
Second, there are TEXT and BLOB types.These types, which come in various sizes, are
for longer text or binary data, respectively. BLOBs, or binary large objects, can hold anything
you like—for example, image or sound data.