On Wed, May 18, 2005 11:15 am, tony yau said:
Hi all,
I try to do the following:
CREATE TABLE IF NOT EXISTS Invoice(
PKey INTEGER,
Received DATETIME,
Cost DECIMAL(10,2),
FileName VARCHAR(50),
RefNum CHAR(10),
PRIMARY KEY (PKey)
) TYPE=MyISAM COMMENT='Invoice Data';
but it keep generating RefNum VARCHAR(10) instead of CHAR(10)
I don't understand, please help (or point me to RTFM page)
WILD GUESS!!!
In *some* impelementations of SQL, the performance benefit of CHAR over
VARCHAR is lost after the first VARCHAR column.
That's exactly it...
http://dev.mysql.com/doc/mysql/en/silent-column-changes.html
If any column in a table has a variable length, the entire row becomes variable-length as a result. Therefore, if a table contains any variable-length columns (VARCHAR, TEXT, or BLOB), all CHAR columns longer than three characters are changed to VARCHAR columns. This doesn't affect how you use the columns in any way; in MySQL, VARCHAR is just a different way to store characters. MySQL performs this conversion because it saves space and makes table operations faster. See Chapter 14, MySQL Storage Engines and Table Types.