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><H1
><A
NAME="SQL-CREATEVIEW"
></A
>CREATE VIEW</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN41532"
></A
><H2
>Name</H2
>CREATE VIEW -- define a new view</DIV
><A
NAME="AEN41535"
></A
><DIV
CLASS="REFSYNOPSISDIV"
><A
NAME="AEN41537"
></A
><H2
>Synopsis</H2
><PRE
CLASS="SYNOPSIS"
>CREATE [ OR REPLACE ] VIEW <TT
CLASS="REPLACEABLE"
><I
>name</I
></TT
> [ ( <TT
CLASS="REPLACEABLE"
><I
>column_name</I
></TT
> [, ...] ) ] AS <TT
CLASS="REPLACEABLE"
><I
>query</I
></TT
></PRE
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN41542"
></A
><H2
>Description</H2
><P
> <TT
CLASS="COMMAND"
>CREATE VIEW</TT
> defines a view of a query. The view
is not physically materialized. Instead, the query is run every time
the view is referenced in a query.
</P
><P
> <TT
CLASS="COMMAND"
>CREATE OR REPLACE VIEW</TT
> is similar, but if a view
of the same name already exists, it is replaced. You can only replace
a view with a new query that generates the identical set of columns
(i.e., same column names and data types).
</P
><P
> If a schema name is given (for example, <TT
CLASS="LITERAL"
>CREATE VIEW
myschema.myview ...</TT
>) then the view is created in the
specified schema. Otherwise it is created in the current schema.
The view name must be distinct from the name of any other view, table,
sequence, or index in the same schema.
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN41550"
></A
><H2
>Parameters</H2
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
><TT
CLASS="REPLACEABLE"
><I
>name</I
></TT
></DT
><DD
><P
> The name (optionally schema-qualified) of a view to be created.
</P
></DD
><DT
><TT
CLASS="REPLACEABLE"
><I
>column_name</I
></TT
></DT
><DD
><P
> An optional list of names to be used for columns of the view.
If not given, the column names are deduced from the query.
</P
></DD
><DT
><TT
CLASS="REPLACEABLE"
><I
>query</I
></TT
></DT
><DD
><P
> A query (that is, a <TT
CLASS="COMMAND"
>SELECT</TT
> statement) which will
provide the columns and rows of the view.
</P
><P
> Refer to <A
HREF="sql-select.html"
><I
>SELECT</I
></A
>
for more information about valid queries.
</P
></DD
></DL
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN41571"
></A
><H2
>Notes</H2
><P
> Currently, views are read only: the system will not allow an insert,
update, or delete on a view. You can get the effect of an updatable
view by creating rules that rewrite inserts, etc. on the view into
appropriate actions on other tables. For more information see
<A
HREF="sql-createrule.html"
><I
>CREATE RULE</I
></A
>.
</P
><P
> Use the <TT
CLASS="COMMAND"
>DROP VIEW</TT
> statement to drop views.
</P
><P
> Be careful that the names and types of the view's columns will be
assigned the way you want. For example,
</P><PRE
CLASS="PROGRAMLISTING"
>CREATE VIEW vista AS SELECT 'Hello World';</PRE
><P>
is bad form in two ways: the column name defaults to <TT
CLASS="LITERAL"
>?column?</TT
>,
and the column data type defaults to <TT
CLASS="TYPE"
>unknown</TT
>. If you want a
string literal in a view's result, use something like
</P><PRE
CLASS="PROGRAMLISTING"
>CREATE VIEW vista AS SELECT text 'Hello World' AS hello;</PRE
><P>
</P
><P
> Access to tables referenced in the view is determined by permissions of
the view owner. However, functions called in the view are treated the
same as if they had been called directly from the query using the view.
Therefore the user of a view must have permissions to call all functions
used by the view.
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN41583"
></A
><H2
>Examples</H2
><P
> Create a view consisting of all comedy films:
</P><PRE
CLASS="PROGRAMLISTING"
>CREATE VIEW comedies AS
SELECT *
FROM films
WHERE kind = 'Comedy';</PRE
><P>
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN41587"
></A
><H2
>Compatibility</H2
><P
> The SQL standard specifies some additional capabilities for the
<TT
CLASS="COMMAND"
>CREATE VIEW</TT
> statement:
</P><PRE
CLASS="SYNOPSIS"
>CREATE VIEW <TT
CLASS="REPLACEABLE"
><I
>name</I
></TT
> [ ( <TT
CLASS="REPLACEABLE"
><I
>column</I
></TT
> [, ...] ) ]
AS query
[ WITH [ CASCADE | LOCAL ] CHECK OPTION ]</PRE
><P>
</P
><P
> The optional clauses for the full SQL command are:
<P
></P
></P><DIV
CLASS="VARIABLELIST"
><DL
><DT
><TT
CLASS="LITERAL"
>CHECK OPTION</TT
></DT
><DD
><P
> This option has to do with updatable views. All
<TT
CLASS="COMMAND"
>INSERT</TT
> and <TT
CLASS="COMMAND"
>UPDATE</TT
> commands on the view
will be checked to ensure data satisfy the view-defining
condition (that is, the new data would be visible through the
view). If they do not, the update will be rejected.
</P
></DD
><DT
><TT
CLASS="LITERAL"
>LOCAL</TT
></DT
><DD
><P
> Check for integrity on this view.
</P
></DD
><DT
><TT
CLASS="LITERAL"
>CASCADE</TT
></DT
><DD
><P
> Check for integrity on this view and on any dependent
view. <TT
CLASS="LITERAL"
>CASCADE</TT
> is assumed if neither
<TT
CLASS="LITERAL"
>CASCADE</TT
> nor <TT
CLASS="LITERAL"
>LOCAL</TT
> is specified.
</P
></DD
></DL
></DIV
><P>
</P
><P
> <TT
CLASS="COMMAND"
>CREATE OR REPLACE VIEW</TT
> is a
<SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> language extension.
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN41619"
></A
><H2
>See Also</H2
><A
HREF="sql-dropview.html"
><I
>DROP VIEW</I
></A
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