Defines the type of database server used in this Query. Possible values for this property are -1 - stUnknown: Undefined (default), 0 - stAccess: Access-type database, 1 - stOracle: Oracle-type database, 2 - stSqlServer: SQL Server-type database, 3 - stPostgreSQL: PostgreSQL-type database, or 4 - stMySQL: MySQL-type database.