When a new BLOB object is created, SESAM/SQL generates an REF value. You can use this value in the columns of any required table to reference the BLOB object. For this reason, the REF columns are defined in base tables. The syntax used for column definition is described in section “Column”.
Alongside the data type CHAR(237), the REF column also contains the REF value of the class as the default value. Certain SESAM-CLI calls, for example for the creation of a new BLOB object, may require the REF value of the class.
A REF value has the basic structure: ss/tt?UID=uuuu&OID=nn
ss tt uuuu | is the simple schema name of the BLOB table without a database name. is the simple table name of the BLOB table without a schema or database name. is a unique ID number for the BLOB object which consists of 32 hexadecimal digits. In the case of the class REF value, all the digits are 0. |
nn | is the number of the BLOB object in the BLOB table. In the case of the class REF value, this number is 0. |
Two REF values are then identical when they designate the same BLOB object. If two REF values are different then they also reference different BLOB objects. In contrast, their BLOB values may be different. If a BLOB object is deleted then its associated REF value can never again designate a BLOB object.