- Design criteria of
NOSQL systems:
- SQL's
(strict) structured data model
is too restrictive !!!
- Data stored in NOSQL systems has a structure that does not comform to traditional table-based structure
- SQL's
(strict) structured data model
is too restrictive !!!
- Data models in
NOSQL systems:
- Do not
use any
data description schema
- Some
NOSQL systems
use Semi-structured
self-describing
data
Examples:
- XML documents:
Example:
<menu id="file" value="File"> <popup> <menuitem value="New" onclick="CreateNewDoc()" /> <menuitem value="Open" onclick="OpenDoc()" /> <menuitem value="Close" onclick="CloseDoc()" /> </popup> </menu>
- JSON documents
Example:
{ "menu": { "id": "file", "value": "File", "popup": { "menuitem": [ {"value": "New", "onclick": "CreateNewDoc()"}, {"value": "Open", "onclick": "OpenDoc()"}, {"value": "Close", "onclick": "CloseDoc()"} ] } } }
- XML documents:
- Other
NOSQL systems does
not specify
any schema
Example:
- In key-value
NoSQL databases
(discussed later),
the value stored
can be
anything:
No structure is imposed of the value part
- The application program that access the data is responsible to structure in the data stored
- In key-value
NoSQL databases
(discussed later),
the value stored
can be
anything:
- Do not
use any
data description schema
- Fact:
- Due to unstructured data, NOSQL system cannot provide power operations in query language that are available in SQL systems
- Functionality available
in NOSQL systems:
- Completely unstructured data:
CRUD operations
- Create (insert data)
- Read (access data)
- Update (modify data)
- Delete (remove data)
- Semi-structured data
(such as XML):
SCRUD operations
- Search (lookup data using limited search criteria)
- Create (insert data)
- Read (access data)
- Update (modify data)
- Delete (remove data)
- Completely unstructured data:
CRUD operations