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136 lines
4.2 KiB
Plaintext
136 lines
4.2 KiB
Plaintext
.\\" auto-generated by docbook2man-spec $Revision: 1.1.1.1 $
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.TH "CREATE VIEW" "" "2005-11-05" "SQL - Language Statements" "SQL Commands"
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.SH NAME
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CREATE VIEW \- define a new view
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.SH SYNOPSIS
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.sp
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.nf
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CREATE [ OR REPLACE ] [ TEMP | TEMPORARY ] VIEW \fIname\fR [ ( \fIcolumn_name\fR [, ...] ) ]
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AS \fIquery\fR
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.sp
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.fi
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.SH "DESCRIPTION"
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.PP
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\fBCREATE VIEW\fR defines a view of a query. The view
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is not physically materialized. Instead, the query is run every time
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the view is referenced in a query.
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.PP
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\fBCREATE OR REPLACE VIEW\fR is similar, but if a view
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of the same name already exists, it is replaced. You can only replace
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a view with a new query that generates the identical set of columns
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(i.e., same column names and data types).
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.PP
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If a schema name is given (for example, CREATE VIEW
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myschema.myview ...) then the view is created in the specified
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schema. Otherwise it is created in the current schema. Temporary
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views exist in a special schema, so a schema name may not be given
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when creating a temporary view. The name of the view must be
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distinct from the name of any other view, table, sequence, or index
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in the same schema.
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.SH "PARAMETERS"
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.TP
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\fBTEMPORARY or TEMP\fR
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If specified, the view is created as a temporary view.
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Temporary views are automatically dropped at the end of the
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current session. Existing
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permanent relations with the same name are not visible to the
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current session while the temporary view exists, unless they are
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referenced with schema-qualified names.
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If any of the tables referenced by the view are temporary,
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the view is created as a temporary view (whether
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TEMPORARY is specified or not).
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.TP
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\fB\fIname\fB\fR
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The name (optionally schema-qualified) of a view to be created.
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.TP
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\fB\fIcolumn_name\fB\fR
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An optional list of names to be used for columns of the view.
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If not given, the column names are deduced from the query.
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.TP
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\fB\fIquery\fB\fR
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A query (that is, a \fBSELECT\fR statement) which will
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provide the columns and rows of the view.
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Refer to SELECT [\fBselect\fR(l)]
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for more information about valid queries.
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.SH "NOTES"
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.PP
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Currently, views are read only: the system will not allow an insert,
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update, or delete on a view. You can get the effect of an updatable
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view by creating rules that rewrite inserts, etc. on the view into
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appropriate actions on other tables. For more information see
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CREATE RULE [\fBcreate_rule\fR(l)].
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.PP
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Use the DROP VIEW [\fBdrop_view\fR(l)]
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statement to drop views.
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.PP
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Be careful that the names and types of the view's columns will be
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assigned the way you want. For example,
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.sp
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.nf
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CREATE VIEW vista AS SELECT 'Hello World';
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.sp
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.fi
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is bad form in two ways: the column name defaults to ?column?,
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and the column data type defaults to \fBunknown\fR. If you want a
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string literal in a view's result, use something like
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.sp
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.nf
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CREATE VIEW vista AS SELECT text 'Hello World' AS hello;
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.sp
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.fi
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.PP
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Access to tables referenced in the view is determined by permissions of
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the view owner. However, functions called in the view are treated the
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same as if they had been called directly from the query using the view.
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Therefore the user of a view must have permissions to call all functions
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used by the view.
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.SH "EXAMPLES"
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.PP
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Create a view consisting of all comedy films:
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.sp
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.nf
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CREATE VIEW comedies AS
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SELECT *
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FROM films
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WHERE kind = 'Comedy';
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.sp
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.fi
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.SH "COMPATIBILITY"
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.PP
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The SQL standard specifies some additional capabilities for the
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\fBCREATE VIEW\fR statement:
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.sp
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.nf
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CREATE VIEW \fIname\fR [ ( \fIcolumn_name\fR [, ...] ) ]
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AS \fIquery\fR
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[ WITH [ CASCADED | LOCAL ] CHECK OPTION ]
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.sp
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.fi
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.PP
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The optional clauses for the full SQL command are:
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.TP
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\fBCHECK OPTION\fR
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This option has to do with updatable views. All
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\fBINSERT\fR and \fBUPDATE\fR commands on the view
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will be checked to ensure data satisfy the view-defining
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condition (that is, the new data would be visible through the
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view). If they do not, the update will be rejected.
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.TP
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\fBLOCAL\fR
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Check for integrity on this view.
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.TP
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\fBCASCADED\fR
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Check for integrity on this view and on any dependent
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view. CASCADED is assumed if neither
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CASCADED nor LOCAL is specified.
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.PP
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.PP
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\fBCREATE OR REPLACE VIEW\fR is a
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PostgreSQL language extension.
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So is the concept of a temporary view.
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.SH "SEE ALSO"
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DROP VIEW [\fBdrop_view\fR(l)]
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