When accessing a Progress Database using BRIO where the Progress Database does contain fields with the type "mandatory" - you will encounter the following problem :
brioqry 144-600 EXIT SQLExecDirect with return code -1 (SQL_ERROR) HSTMT 01D91E10 UCHAR * 0x00DE70A4 SDWORD 0 DIAG [S1090] [Microsoft][ODBC Driver Manager] Invalid string or buffer length (0)
Changing the field type from mandatory solves the issue.