Oracle
When an XML Schema is generated from an Oracle database (DB), the Oracle DB datatypes are converted to XML Schema datatypes as listed in the table below.
Oracle Datatype  | XML Schema Datatype  | 
ROWID  | xs:ID  | 
CHAR  | xs:string  | 
NCHAR  | xs:string  | 
VARCHAR2  | xs:string  | 
NVARCHAR2  | xs:string  | 
CLOB  | xs:string  | 
NCLOB  | xs:string  | 
NUMBER (with check constraint applied)*  | xs:boolean  | 
NUMBER  | xs:decimal  | 
FLOAT  | xs:double  | 
DATE  | xs:dateTime  | 
INTERVAL YEAR TO MONTH  | xs:gYearMonth  | 
BLOB  | xs:base64Binary  | 
| * | If a check constraint is applied to a column of datatype NUMBER, and the check constraint checks for the values 0 or 1, then the NUMBER datatype for this column will be converted to an XML Schema datatype of xs:boolean. This mechanism is useful for generating an xs:boolean datatype in the generated XML Schema. |