DT_STR 类型和 DT_WSTR 类型有什么区别？

DT_STR

A null-terminated ANSI/MBCS character string with a maximum length of 8000 characters. (If a column value contains additional null terminators, the string will be truncated at the occurrence of the first null.)

DT_WSTR

A null-terminated Unicode character string with a maximum length of 4000 characters. (If a column value contains additional null terminators, the string will be truncated at the occurrence of the first null.)

reference:
http://msdn.microsoft.com/en-us/library/ms141036.aspx

The difference is the same as between varchar and nvarchar: non-UNICODE vs. UNICODE.