DB2 View

DB2 TABLE DB2 Types of VIEWS

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VIEW is nothing but the table which can be derived from one or more tables.

In other words, the view can be defined as “ The Table which can be derived from one or more tables based on selection criteria”.

A VIEW is an alternative representation of data which is derived from one or more tables.

MAX up to 15 tables can be used to create the view.

VIEW can combine the data from different tables.

VIEW can omit the columns from base tables and can only create on with some columns of the base tables.

VIEW can contain all the columns or some columns from the table.

CREATE VIEW is used to create the VIEW.

VIEW is temporary table in storage point of view and no memory will be allocated.

A VIEW can be created on single table or more than one table.

If a VIEW created with all the tables of a single table, then the data can be inserted by referring the view name in INSERT.


Advantages:


Makes data easier to use by representing the data from more than one table’s as a single table.

Restrict the access to the base tables and providing the access to the view can increase security to base table data.

Increasing controlled access over the database.

Can able to hide the complex queries and makes the end user life easy by representing the data in single table from more than one table.

Views can have the derived columns, apart from the retrieved columns.


Syntax:


CREATE VIEW View name[Column-names] AS
	(SELECT *[column-names] FROM database-name.tablespace-name.table-name) 
	 ON database-name.tablespace-name


SYSCAT.VIEWS contains the VIEWs complete information.

A VIEW is unchanged, if the base table altered when the VIEW is created on full table.


SYSCAT.VIEWS:


Field nameData typeDescription
VIEWSCHEMAVARCHAR(128)Along with VIEWNAME, the qualified name of a view or table that is used to define a materialized query table or staging table
VIEWNAMEVARCHAR(128)Along with VIEWSCHEMA, the qualified name of a view or table that is used to define a materialized query table or staging table
DEFINERVARCHAR(128)Authorization ID of the creator of the view
SEQNOSMALLINTAlways 1
VIEWCHECKCHAR(1) The type of view checking
  • N = No check option
  • L = Local check option
  • C = Cascaded check option
READONLYCHAR(1)Y = Read-only view because of its definition
or
N = Not read-only view
VALIDCHAR(1)Y = Valid view or materialized query table definition valid
or
X = Inoperative view or materialized query table definition; must be re-created
QUALIFIERVARCHAR(128)Contains value of the default schema at the time of object definition
FUNC_PATHVARCHAR(254)The SQL path of the view creator at the time the view was defined
When the view is used in data manipulation statements, this path must be used to resolve function calls in the view.
TEXTCLOB(64K)Text of the CREATE VIEW statement

Note:  The above table information is collected from Internet.


Practical Example:


DB2 Code:


CREATE VIEW USER_DETAILS_V AS 
	(SELECT * FROM USER_DETAILS )
	ON MTH1DB.MFTHTS
 

DB2 TABLE DB2 Types of VIEWS

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