1·LONG VARCHAR所允许的长度大于32672，这将导致数据的截断。
The length allowed for a LONG VARCHAR is greater than 32672 and this could result in truncation of data.
2·Sybase：如果源表具有数据类型为LONG VARCHAR的列，就要用数据类型VARCHAR(32672)创建别名。
Sybase: If the source table has a column data type of LONG VARCHAR, the nickname is created with a data type of VARCHAR (32672).