4.5. Flexibility
In conventional relational databases, one must first model
the data in the initial phase of the development. Data modelling
is restricted here by the permissible number of columns
of the database management system. In contrast, both the
NoSQL database design and the XML structure used in the
XML databases are more fiexible in that there is no need
to pre-define the required number of columns. Data with
complex structures can always be added subsequently. Fur
storage when compared to NoSQL approaches
of clinical notes. The number of rows is thus kept to a minther,
re-design of schema is not required when the content is
changed since the schema is generalized for any clinical concepts.
In particular, for XML databases containing clinical data
represented with XML data types, queries can be performed
conveniently with the X-Query language which is sufficient for
performing most queries encountered in conventional relational
database tables [31]. Between the two XML approaches,
it is necessary to write additional SQL codes in approach II in ported
by MS-SQL. This procedure is not required for native
XML database developed with eXist, where raw data are simply
imported as files.