When a VARCHAR column has this default value, the column is the filename column in an external blob definition.
When a column has this type of default, the system table TableSchema.SYS_COLUMN's column_default_value column will contain
the prefix and extension strings found in the external blob definition, in the form 'prefix|extension'.
The default value of existing tables can be determined by querying the system table TableSchema.SYS_COLUMNS's column_default
column.
Syntax