mysql text 长度
http://justdo2008.iteye.com/blog/576552
mysql的text类型有64K长度限制的，MEDIUMTEXT中型是2G，LONGTEXT大型是4G .
| 类型 | 最大长度 |
| char | 255 |
| vharchar | 65535 |
| tinyblob tinytext | 255 (2^8-1) |
| BLOB TEXT | 65535 (2^16-1) |
| MEDIUMBLOB MEDIUMTEXT | 16777215 (2^24-1) |
| LONGBLOB LONGTEXT | 4294967295 (2^32-1) |
| tinyint | -128~127 0~255 |
| bit | tinyint(1) |
| bool | tinyint(1) |
| smallint | -32768~32767 0~65535 |
| mediumint | 16777215 |
| int | 2^32-1 |
| integer | 同int |
| bigint | 2^64 |
| float | |
| double | |
| real | 同double |
| decimal | |
| dec | 同decimal |
| numeric | 同decimal |