Selecting the LO handle

The SELECT statement can select an LO handle of a smart large object from a CLOB, BLOB, or opaque-type column. Because the result of a query is usually the contents of an object, not just its LO handle, the DataBlade® API module must then use the LO handle that the mi_value() or mi_value_by_name() function returns to access the smart-large-object data in its sbspace.

About this task

To select a smart large object from the database:

Procedure

1. Execute the SELECT statement with a DataBlade® API statement-execution function such as mi_exec() or mi_exec_prepared_statement().
2. Obtain the column value that the mi_value() or mi_value_by_name() function passes back in the MI_DATUM structure as appropriate for the control mode of the query:
   • For binary representation, the MI_DATUM structure contains a pointer to an LO handle.
   • For text representation, the MI_DATUM structure contains the hexadecimal dump of an LO handle. To access the smart-large-object data, you must convert the LO handle to its binary representation with mi_lo_from_string().
3. Optional: Ensure that the LO handle is valid with mi_lo_validate().