1CREATE VIEW(7) PostgreSQL 13.4 Documentation CREATE VIEW(7)
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6 CREATE_VIEW - define a new view
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9 CREATE [ OR REPLACE ] [ TEMP | TEMPORARY ] [ RECURSIVE ] VIEW name [ ( column_name [, ...] ) ]
10 [ WITH ( view_option_name [= view_option_value] [, ... ] ) ]
11 AS query
12 [ WITH [ CASCADED | LOCAL ] CHECK OPTION ]
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15 CREATE VIEW defines a view of a query. The view is not physically
16 materialized. Instead, the query is run every time the view is
17 referenced in a query.
18 CREATE OR REPLACE VIEW is similar, but if a view of the same name
20 already exists, it is replaced. The new query must generate the same
21 columns that were generated by the existing view query (that is, the
22 same column names in the same order and with the same data types), but
23 it may add additional columns to the end of the list. The calculations
24 giving rise to the output columns may be completely different.
25 If a schema name is given (for example, CREATE VIEW myschema.myview
27 ...) then the view is created in the specified schema. Otherwise it is
28 created in the current schema. Temporary views exist in a special
29 schema, so a schema name cannot be given when creating a temporary
30 view. The name of the view must be distinct from the name of any other
31 view, table, sequence, index or foreign table in the same schema.
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34 TEMPORARY or TEMP
35 If specified, the view is created as a temporary view. Temporary
36 views are automatically dropped at the end of the current session.
37 Existing permanent relations with the same name are not visible to
38 the current session while the temporary view exists, unless they
39 are referenced with schema-qualified names.
40 If any of the tables referenced by the view are temporary, the view
42 is created as a temporary view (whether TEMPORARY is specified or
43 not).
44 RECURSIVE
46 Creates a recursive view. The syntax
47 CREATE RECURSIVE VIEW [ schema . ] view_name (column_names) AS SELECT ...;
49 is equivalent to
51 CREATE VIEW [ schema . ] view_name AS WITH RECURSIVE view_name (column_names) AS (SELECT ...) SELECT column_names FROM view_name;
53 A view column name list must be specified for a recursive view.
55 name
57 The name (optionally schema-qualified) of a view to be created.
58 column_name
60 An optional list of names to be used for columns of the view. If
61 not given, the column names are deduced from the query.
62 WITH ( view_option_name [= view_option_value] [, ... ] )
64 This clause specifies optional parameters for a view; the following
65 parameters are supported:
66 check_option (enum)
68 This parameter may be either local or cascaded, and is
69 equivalent to specifying WITH [ CASCADED | LOCAL ] CHECK OPTION
70 (see below). This option can be changed on existing views using
71 ALTER VIEW (ALTER_VIEW(7)).
72 security_barrier (boolean)
74 This should be used if the view is intended to provide
75 row-level security. See Section 40.5 for full details.
76 query
78 A SELECT(7) or VALUES(7) command which will provide the columns and
79 rows of the view.
80 WITH [ CASCADED | LOCAL ] CHECK OPTION
82 This option controls the behavior of automatically updatable views.
83 When this option is specified, INSERT and UPDATE commands on the
84 view will be checked to ensure that new rows satisfy the
85 view-defining condition (that is, the new rows are checked to
86 ensure that they are visible through the view). If they are not,
87 the update will be rejected. If the CHECK OPTION is not specified,
88 INSERT and UPDATE commands on the view are allowed to create rows
89 that are not visible through the view. The following check options
90 are supported:
91 LOCAL
93 New rows are only checked against the conditions defined
94 directly in the view itself. Any conditions defined on
95 underlying base views are not checked (unless they also specify
96 the CHECK OPTION).
97 CASCADED
99 New rows are checked against the conditions of the view and all
100 underlying base views. If the CHECK OPTION is specified, and
101 neither LOCAL nor CASCADED is specified, then CASCADED is
102 assumed.
103 The CHECK OPTION may not be used with RECURSIVE views.
105 Note that the CHECK OPTION is only supported on views that are
107 automatically updatable, and do not have INSTEAD OF triggers or
108 INSTEAD rules. If an automatically updatable view is defined on top
109 of a base view that has INSTEAD OF triggers, then the LOCAL CHECK
110 OPTION may be used to check the conditions on the automatically
111 updatable view, but the conditions on the base view with INSTEAD OF
112 triggers will not be checked (a cascaded check option will not
113 cascade down to a trigger-updatable view, and any check options
114 defined directly on a trigger-updatable view will be ignored). If
115 the view or any of its base relations has an INSTEAD rule that
116 causes the INSERT or UPDATE command to be rewritten, then all check
117 options will be ignored in the rewritten query, including any
118 checks from automatically updatable views defined on top of the
119 relation with the INSTEAD rule.
120
122 Use the DROP VIEW (DROP_VIEW(7)) statement to drop views.
123 Be careful that the names and types of the view's columns will be
125 assigned the way you want. For example:
126 CREATE VIEW vista AS SELECT 'Hello World';
128 is bad form because the column name defaults to ?column?; also, the
130 column data type defaults to text, which might not be what you wanted.
131 Better style for a string literal in a view's result is something like:
132 CREATE VIEW vista AS SELECT text 'Hello World' AS hello;
134 Access to tables referenced in the view is determined by permissions of
136 the view owner. In some cases, this can be used to provide secure but
137 restricted access to the underlying tables. However, not all views are
138 secure against tampering; see Section 40.5 for details. Functions
139 called in the view are treated the same as if they had been called
140 directly from the query using the view. Therefore the user of a view
141 must have permissions to call all functions used by the view.
142 When CREATE OR REPLACE VIEW is used on an existing view, only the
144 view's defining SELECT rule is changed. Other view properties,
145 including ownership, permissions, and non-SELECT rules, remain
146 unchanged. You must own the view to replace it (this includes being a
147 member of the owning role).
148 Updatable Views
150 Simple views are automatically updatable: the system will allow INSERT,
151 UPDATE and DELETE statements to be used on the view in the same way as
152 on a regular table. A view is automatically updatable if it satisfies
153 all of the following conditions:
154 • The view must have exactly one entry in its FROM list, which must
156 be a table or another updatable view.
157 • The view definition must not contain WITH, DISTINCT, GROUP BY,
159 HAVING, LIMIT, or OFFSET clauses at the top level.
160 • The view definition must not contain set operations (UNION,
162 INTERSECT or EXCEPT) at the top level.
163 • The view's select list must not contain any aggregates, window
165 functions or set-returning functions.
166 An automatically updatable view may contain a mix of updatable and
168 non-updatable columns. A column is updatable if it is a simple
169 reference to an updatable column of the underlying base relation;
170 otherwise the column is read-only, and an error will be raised if an
171 INSERT or UPDATE statement attempts to assign a value to it.
172 If the view is automatically updatable the system will convert any
174 INSERT, UPDATE or DELETE statement on the view into the corresponding
175 statement on the underlying base relation. INSERT statements that have
176 an ON CONFLICT UPDATE clause are fully supported.
177 If an automatically updatable view contains a WHERE condition, the
179 condition restricts which rows of the base relation are available to be
180 modified by UPDATE and DELETE statements on the view. However, an
181 UPDATE is allowed to change a row so that it no longer satisfies the
182 WHERE condition, and thus is no longer visible through the view.
183 Similarly, an INSERT command can potentially insert base-relation rows
184 that do not satisfy the WHERE condition and thus are not visible
185 through the view (ON CONFLICT UPDATE may similarly affect an existing
186 row not visible through the view). The CHECK OPTION may be used to
187 prevent INSERT and UPDATE commands from creating such rows that are not
188 visible through the view.
189 If an automatically updatable view is marked with the security_barrier
191 property then all the view's WHERE conditions (and any conditions using
192 operators which are marked as LEAKPROOF) will always be evaluated
193 before any conditions that a user of the view has added. See
194 Section 40.5 for full details. Note that, due to this, rows which are
195 not ultimately returned (because they do not pass the user's WHERE
196 conditions) may still end up being locked. EXPLAIN can be used to see
197 which conditions are applied at the relation level (and therefore do
198 not lock rows) and which are not.
199 A more complex view that does not satisfy all these conditions is
201 read-only by default: the system will not allow an insert, update, or
202 delete on the view. You can get the effect of an updatable view by
203 creating INSTEAD OF triggers on the view, which must convert attempted
204 inserts, etc. on the view into appropriate actions on other tables. For
205 more information see CREATE TRIGGER (CREATE_TRIGGER(7)). Another
206 possibility is to create rules (see CREATE RULE (CREATE_RULE(7))), but
207 in practice triggers are easier to understand and use correctly.
208 Note that the user performing the insert, update or delete on the view
210 must have the corresponding insert, update or delete privilege on the
211 view. In addition the view's owner must have the relevant privileges on
212 the underlying base relations, but the user performing the update does
213 not need any permissions on the underlying base relations (see
214 Section 40.5).
215
217 Create a view consisting of all comedy films:
218 CREATE VIEW comedies AS
220 SELECT *
221 FROM films
222 WHERE kind = 'Comedy';
223 This will create a view containing the columns that are in the film
225 table at the time of view creation. Though * was used to create the
226 view, columns added later to the table will not be part of the view.
227 Create a view with LOCAL CHECK OPTION:
229 CREATE VIEW universal_comedies AS
231 SELECT *
232 FROM comedies
233 WHERE classification = 'U'
234 WITH LOCAL CHECK OPTION;
235 This will create a view based on the comedies view, showing only films
237 with kind = 'Comedy' and classification = 'U'. Any attempt to INSERT or
238 UPDATE a row in the view will be rejected if the new row doesn't have
239 classification = 'U', but the film kind will not be checked.
240 Create a view with CASCADED CHECK OPTION:
242 CREATE VIEW pg_comedies AS
244 SELECT *
245 FROM comedies
246 WHERE classification = 'PG'
247 WITH CASCADED CHECK OPTION;
248 This will create a view that checks both the kind and classification of
250 new rows.
251 Create a view with a mix of updatable and non-updatable columns:
253 CREATE VIEW comedies AS
255 SELECT f.*,
256 country_code_to_name(f.country_code) AS country,
257 (SELECT avg(r.rating)
258 FROM user_ratings r
259 WHERE r.film_id = f.id) AS avg_rating
260 FROM films f
261 WHERE f.kind = 'Comedy';
262 This view will support INSERT, UPDATE and DELETE. All the columns from
264 the films table will be updatable, whereas the computed columns country
265 and avg_rating will be read-only.
266 Create a recursive view consisting of the numbers from 1 to 100:
268 CREATE RECURSIVE VIEW public.nums_1_100 (n) AS
270 VALUES (1)
271 UNION ALL
272 SELECT n+1 FROM nums_1_100 WHERE n < 100;
273 Notice that although the recursive view's name is schema-qualified in
275 this CREATE, its internal self-reference is not schema-qualified. This
276 is because the implicitly-created CTE's name cannot be
277 schema-qualified.
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280 CREATE OR REPLACE VIEW is a PostgreSQL language extension. So is the
281 concept of a temporary view. The WITH ( ... ) clause is an extension as
282 well.
283
285 ALTER VIEW (ALTER_VIEW(7)), DROP VIEW (DROP_VIEW(7)), CREATE
286 MATERIALIZED VIEW (CREATE_MATERIALIZED_VIEW(7))
287PostgreSQL 13.4 2021 CREATE VIEW(7)