> For the complete documentation index, see [llms.txt](https://lin-4.gitbook.io/database-and-relative/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://lin-4.gitbook.io/database-and-relative/chapter1.md).

# database

The CRUD cycle describes the elemental functions of a persistent database. CRUD stands for Create, Read, Update and Delete. (Retrieve may occasionally be substituted for Read.) These functions are also descriptive of the [data life cycle](http://searchstorage.techtarget.com/definition/data-life-cycle-management).

## 2. Clob vs Blob

LOB stands for large object, a stream of data stored in a database. Maximum capacity of a LOB is (4 gigabytes-1) bytes. In Oracle three kinds of LOB data type exist:

* **BLOB** datetype stores unstructured binary large objects. BLOB objects can be thought of as bitstreams with no character set semantics.
* The **CLOB** datatype stores single-byte and multibyte character data. Both fixed-width and variable-width character sets are supported, and both use the database character set.
* The **NCLOB** datatype stores Unicode data.

## 3. Truncate VS delete

Truncate: removes all data from a table, typically bypassing a number of integrity enforcing mechanisms.

delete: delete existing records in a table.

### 4. View vs Materalized View vs Table

Materalized view: disk based and are updated periodidcally based upon the query definition.

view: virtual only and run the query definition each time they are accessed.