1CREATE VIEW(7) PostgreSQL 12.2 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 (string)
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
79 A SELECT(7) or VALUES(7) command which will provide the columns and
80 rows of the view.
81 WITH [ CASCADED | LOCAL ] CHECK OPTION
83 This option controls the behavior of automatically updatable views.
84 When this option is specified, INSERT and UPDATE commands on the
85 view will be checked to ensure that new rows satisfy the
86 view-defining condition (that is, the new rows are checked to
87 ensure that they are visible through the view). If they are not,
88 the update will be rejected. If the CHECK OPTION is not specified,
89 INSERT and UPDATE commands on the view are allowed to create rows
90 that are not visible through the view. The following check options
91 are supported:
92 LOCAL
94 New rows are only checked against the conditions defined
95 directly in the view itself. Any conditions defined on
96 underlying base views are not checked (unless they also specify
97 the CHECK OPTION).
98 CASCADED
100 New rows are checked against the conditions of the view and all
101 underlying base views. If the CHECK OPTION is specified, and
102 neither LOCAL nor CASCADED is specified, then CASCADED is
103 assumed.
104 The CHECK OPTION may not be used with RECURSIVE views.
106 Note that the CHECK OPTION is only supported on views that are
108 automatically updatable, and do not have INSTEAD OF triggers or
109 INSTEAD rules. If an automatically updatable view is defined on top
110 of a base view that has INSTEAD OF triggers, then the LOCAL CHECK
111 OPTION may be used to check the conditions on the automatically
112 updatable view, but the conditions on the base view with INSTEAD OF
113 triggers will not be checked (a cascaded check option will not
114 cascade down to a trigger-updatable view, and any check options
115 defined directly on a trigger-updatable view will be ignored). If
116 the view or any of its base relations has an INSTEAD rule that
117 causes the INSERT or UPDATE command to be rewritten, then all check
118 options will be ignored in the rewritten query, including any
119 checks from automatically updatable views defined on top of the
120 relation with the INSTEAD rule.
121
123 Use the DROP VIEW (DROP_VIEW(7)) statement to drop views.
124 Be careful that the names and types of the view's columns will be
126 assigned the way you want. For example:
127 CREATE VIEW vista AS SELECT 'Hello World';
129 is bad form because the column name defaults to ?column?; also, the
131 column data type defaults to text, which might not be what you wanted.
132 Better style for a string literal in a view's result is something like:
133 CREATE VIEW vista AS SELECT text 'Hello World' AS hello;
135 Access to tables referenced in the view is determined by permissions of
137 the view owner. In some cases, this can be used to provide secure but
138 restricted access to the underlying tables. However, not all views are
139 secure against tampering; see Section 40.5 for details. Functions
140 called in the view are treated the same as if they had been called
141 directly from the query using the view. Therefore the user of a view
142 must have permissions to call all functions used by the view.
143 When CREATE OR REPLACE VIEW is used on an existing view, only the
145 view's defining SELECT rule is changed. Other view properties,
146 including ownership, permissions, and non-SELECT rules, remain
147 unchanged. You must own the view to replace it (this includes being a
148 member of the owning role).
149 Updatable Views
151 Simple views are automatically updatable: the system will allow INSERT,
152 UPDATE and DELETE statements to be used on the view in the same way as
153 on a regular table. A view is automatically updatable if it satisfies
154 all of the following conditions:
155 · The view must have exactly one entry in its FROM list, which must
157 be a table or another updatable view.
158 · The view definition must not contain WITH, DISTINCT, GROUP BY,
160 HAVING, LIMIT, or OFFSET clauses at the top level.
161 · The view definition must not contain set operations (UNION,
163 INTERSECT or EXCEPT) at the top level.
164 · The view's select list must not contain any aggregates, window
166 functions or set-returning functions.
167 An automatically updatable view may contain a mix of updatable and
169 non-updatable columns. A column is updatable if it is a simple
170 reference to an updatable column of the underlying base relation;
171 otherwise the column is read-only, and an error will be raised if an
172 INSERT or UPDATE statement attempts to assign a value to it.
173 If the view is automatically updatable the system will convert any
175 INSERT, UPDATE or DELETE statement on the view into the corresponding
176 statement on the underlying base relation. INSERT statements that have
177 an ON CONFLICT UPDATE clause are fully supported.
178 If an automatically updatable view contains a WHERE condition, the
180 condition restricts which rows of the base relation are available to be
181 modified by UPDATE and DELETE statements on the view. However, an
182 UPDATE is allowed to change a row so that it no longer satisfies the
183 WHERE condition, and thus is no longer visible through the view.
184 Similarly, an INSERT command can potentially insert base-relation rows
185 that do not satisfy the WHERE condition and thus are not visible
186 through the view (ON CONFLICT UPDATE may similarly affect an existing
187 row not visible through the view). The CHECK OPTION may be used to
188 prevent INSERT and UPDATE commands from creating such rows that are not
189 visible through the view.
190 If an automatically updatable view is marked with the security_barrier
192 property then all the view's WHERE conditions (and any conditions using
193 operators which are marked as LEAKPROOF) will always be evaluated
194 before any conditions that a user of the view has added. See
195 Section 40.5 for full details. Note that, due to this, rows which are
196 not ultimately returned (because they do not pass the user's WHERE
197 conditions) may still end up being locked. EXPLAIN can be used to see
198 which conditions are applied at the relation level (and therefore do
199 not lock rows) and which are not.
200 A more complex view that does not satisfy all these conditions is
202 read-only by default: the system will not allow an insert, update, or
203 delete on the view. You can get the effect of an updatable view by
204 creating INSTEAD OF triggers on the view, which must convert attempted
205 inserts, etc. on the view into appropriate actions on other tables. For
206 more information see CREATE TRIGGER (CREATE_TRIGGER(7)). Another
207 possibility is to create rules (see CREATE RULE (CREATE_RULE(7))), but
208 in practice triggers are easier to understand and use correctly.
209 Note that the user performing the insert, update or delete on the view
211 must have the corresponding insert, update or delete privilege on the
212 view. In addition the view's owner must have the relevant privileges on
213 the underlying base relations, but the user performing the update does
214 not need any permissions on the underlying base relations (see
215 Section 40.5).
216
218 Create a view consisting of all comedy films:
219 CREATE VIEW comedies AS
221 SELECT *
222 FROM films
223 WHERE kind = 'Comedy';
224 This will create a view containing the columns that are in the film
226 table at the time of view creation. Though * was used to create the
227 view, columns added later to the table will not be part of the view.
228 Create a view with LOCAL CHECK OPTION:
230 CREATE VIEW universal_comedies AS
232 SELECT *
233 FROM comedies
234 WHERE classification = 'U'
235 WITH LOCAL CHECK OPTION;
236 This will create a view based on the comedies view, showing only films
238 with kind = 'Comedy' and classification = 'U'. Any attempt to INSERT or
239 UPDATE a row in the view will be rejected if the new row doesn't have
240 classification = 'U', but the film kind will not be checked.
241 Create a view with CASCADED CHECK OPTION:
243 CREATE VIEW pg_comedies AS
245 SELECT *
246 FROM comedies
247 WHERE classification = 'PG'
248 WITH CASCADED CHECK OPTION;
249 This will create a view that checks both the kind and classification of
251 new rows.
252 Create a view with a mix of updatable and non-updatable columns:
254 CREATE VIEW comedies AS
256 SELECT f.*,
257 country_code_to_name(f.country_code) AS country,
258 (SELECT avg(r.rating)
259 FROM user_ratings r
260 WHERE r.film_id = f.id) AS avg_rating
261 FROM films f
262 WHERE f.kind = 'Comedy';
263 This view will support INSERT, UPDATE and DELETE. All the columns from
265 the films table will be updatable, whereas the computed columns country
266 and avg_rating will be read-only.
267 Create a recursive view consisting of the numbers from 1 to 100:
269 CREATE RECURSIVE VIEW public.nums_1_100 (n) AS
271 VALUES (1)
272 UNION ALL
273 SELECT n+1 FROM nums_1_100 WHERE n < 100;
274 Notice that although the recursive view's name is schema-qualified in
276 this CREATE, its internal self-reference is not schema-qualified. This
277 is because the implicitly-created CTE's name cannot be
278 schema-qualified.
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281 CREATE OR REPLACE VIEW is a PostgreSQL language extension. So is the
282 concept of a temporary view. The WITH ( ... ) clause is an extension as
283 well.
284
286 ALTER VIEW (ALTER_VIEW(7)), DROP VIEW (DROP_VIEW(7)), CREATE
287 MATERIALIZED VIEW (CREATE_MATERIALIZED_VIEW(7))
288PostgreSQL 12.2 2020 CREATE VIEW(7)