1CREATE FOREIGN TABLE(7) PostgreSQL 11.6 Documentation CREATE FOREIGN TABLE(7)
2
6 CREATE_FOREIGN_TABLE - define a new foreign table
7
9 CREATE FOREIGN TABLE [ IF NOT EXISTS ] table_name ( [
10 { column_name data_type [ OPTIONS ( option 'value' [, ... ] ) ] [ COLLATE collation ] [ column_constraint [ ... ] ]
11 | table_constraint }
12 [, ... ]
13 ] )
14 [ INHERITS ( parent_table [, ... ] ) ]
15 SERVER server_name
16 [ OPTIONS ( option 'value' [, ... ] ) ]
17 CREATE FOREIGN TABLE [ IF NOT EXISTS ] table_name
19 PARTITION OF parent_table [ (
20 { column_name [ WITH OPTIONS ] [ column_constraint [ ... ] ]
21 | table_constraint }
22 [, ... ]
23 ) ] partition_bound_spec
24 SERVER server_name
25 [ OPTIONS ( option 'value' [, ... ] ) ]
26 where column_constraint is:
28 [ CONSTRAINT constraint_name ]
30 { NOT NULL |
31 NULL |
32 CHECK ( expression ) [ NO INHERIT ] |
33 DEFAULT default_expr }
34 and table_constraint is:
36 [ CONSTRAINT constraint_name ]
38 CHECK ( expression ) [ NO INHERIT ]
39
41 CREATE FOREIGN TABLE creates a new foreign table in the current
42 database. The table will be owned by the user issuing the command.
43 If a schema name is given (for example, CREATE FOREIGN TABLE
45 myschema.mytable ...) then the table is created in the specified
46 schema. Otherwise it is created in the current schema. The name of the
47 foreign table must be distinct from the name of any other foreign
48 table, table, sequence, index, view, or materialized view in the same
49 schema.
50 CREATE FOREIGN TABLE also automatically creates a data type that
52 represents the composite type corresponding to one row of the foreign
53 table. Therefore, foreign tables cannot have the same name as any
54 existing data type in the same schema.
55 If PARTITION OF clause is specified then the table is created as a
57 partition of parent_table with specified bounds.
58 To be able to create a foreign table, you must have USAGE privilege on
60 the foreign server, as well as USAGE privilege on all column types used
61 in the table.
62
64 IF NOT EXISTS
65 Do not throw an error if a relation with the same name already
66 exists. A notice is issued in this case. Note that there is no
67 guarantee that the existing relation is anything like the one that
68 would have been created.
69 table_name
71 The name (optionally schema-qualified) of the table to be created.
72 column_name
74 The name of a column to be created in the new table.
75 data_type
77 The data type of the column. This can include array specifiers. For
78 more information on the data types supported by PostgreSQL, refer
79 to Chapter 8.
80 COLLATE collation
82 The COLLATE clause assigns a collation to the column (which must be
83 of a collatable data type). If not specified, the column data
84 type's default collation is used.
85 INHERITS ( parent_table [, ... ] )
87 The optional INHERITS clause specifies a list of tables from which
88 the new foreign table automatically inherits all columns. Parent
89 tables can be plain tables or foreign tables. See the similar form
90 of CREATE TABLE (CREATE_TABLE(7)) for more details.
91 PARTITION OF parent_table FOR VALUES partition_bound_spec
93 This form can be used to create the foreign table as partition of
94 the given parent table with specified partition bound values. See
95 the similar form of CREATE TABLE (CREATE_TABLE(7)) for more
96 details. Note that it is currently not allowed to create the
97 foreign table as a partition of the parent table if there are
98 UNIQUE indexes on the parent table. (See also ALTER TABLE ATTACH
99 PARTITION.)
100 CONSTRAINT constraint_name
102 An optional name for a column or table constraint. If the
103 constraint is violated, the constraint name is present in error
104 messages, so constraint names like col must be positive can be used
105 to communicate helpful constraint information to client
106 applications. (Double-quotes are needed to specify constraint names
107 that contain spaces.) If a constraint name is not specified, the
108 system generates a name.
109 NOT NULL
111 The column is not allowed to contain null values.
112 NULL
114 The column is allowed to contain null values. This is the default.
115 This clause is only provided for compatibility with non-standard
117 SQL databases. Its use is discouraged in new applications.
118 CHECK ( expression ) [ NO INHERIT ]
120 The CHECK clause specifies an expression producing a Boolean result
121 which each row in the foreign table is expected to satisfy; that
122 is, the expression should produce TRUE or UNKNOWN, never FALSE, for
123 all rows in the foreign table. A check constraint specified as a
124 column constraint should reference that column's value only, while
125 an expression appearing in a table constraint can reference
126 multiple columns.
127 Currently, CHECK expressions cannot contain subqueries nor refer to
129 variables other than columns of the current row. The system column
130 tableoid may be referenced, but not any other system column.
131 A constraint marked with NO INHERIT will not propagate to child
133 tables.
134 DEFAULT default_expr
136 The DEFAULT clause assigns a default data value for the column
137 whose column definition it appears within. The value is any
138 variable-free expression (subqueries and cross-references to other
139 columns in the current table are not allowed). The data type of the
140 default expression must match the data type of the column.
141 The default expression will be used in any insert operation that
143 does not specify a value for the column. If there is no default for
144 a column, then the default is null.
145 server_name
147 The name of an existing foreign server to use for the foreign
148 table. For details on defining a server, see CREATE SERVER
149 (CREATE_SERVER(7)).
150 OPTIONS ( option 'value' [, ...] )
152 Options to be associated with the new foreign table or one of its
153 columns. The allowed option names and values are specific to each
154 foreign data wrapper and are validated using the foreign-data
155 wrapper's validator function. Duplicate option names are not
156 allowed (although it's OK for a table option and a column option to
157 have the same name).
158
160 Constraints on foreign tables (such as CHECK or NOT NULL clauses) are
161 not enforced by the core PostgreSQL system, and most foreign data
162 wrappers do not attempt to enforce them either; that is, the constraint
163 is simply assumed to hold true. There would be little point in such
164 enforcement since it would only apply to rows inserted or updated via
165 the foreign table, and not to rows modified by other means, such as
166 directly on the remote server. Instead, a constraint attached to a
167 foreign table should represent a constraint that is being enforced by
168 the remote server.
169 Some special-purpose foreign data wrappers might be the only access
171 mechanism for the data they access, and in that case it might be
172 appropriate for the foreign data wrapper itself to perform constraint
173 enforcement. But you should not assume that a wrapper does that unless
174 its documentation says so.
175 Although PostgreSQL does not attempt to enforce constraints on foreign
177 tables, it does assume that they are correct for purposes of query
178 optimization. If there are rows visible in the foreign table that do
179 not satisfy a declared constraint, queries on the table might produce
180 incorrect answers. It is the user's responsibility to ensure that the
181 constraint definition matches reality.
182 While rows can be moved from local partitions to a foreign-table
184 partition (provided the foreign data wrapper supports tuple routing),
185 they cannot be moved from a foreign-table partition to another
186 partition.
187
189 Create foreign table films, which will be accessed through the server
190 film_server:
191 CREATE FOREIGN TABLE films (
193 code char(5) NOT NULL,
194 title varchar(40) NOT NULL,
195 did integer NOT NULL,
196 date_prod date,
197 kind varchar(10),
198 len interval hour to minute
199 )
200 SERVER film_server;
201 Create foreign table measurement_y2016m07, which will be accessed
203 through the server server_07, as a partition of the range partitioned
204 table measurement:
205 CREATE FOREIGN TABLE measurement_y2016m07
207 PARTITION OF measurement FOR VALUES FROM ('2016-07-01') TO ('2016-08-01')
208 SERVER server_07;
209
211 The CREATE FOREIGN TABLE command largely conforms to the SQL standard;
212 however, much as with CREATE TABLE, NULL constraints and zero-column
213 foreign tables are permitted. The ability to specify column default
214 values is also a PostgreSQL extension. Table inheritance, in the form
215 defined by PostgreSQL, is nonstandard.
216
218 ALTER FOREIGN TABLE (ALTER_FOREIGN_TABLE(7)), DROP FOREIGN TABLE
219 (DROP_FOREIGN_TABLE(7)), CREATE TABLE (CREATE_TABLE(7)), CREATE SERVER
220 (CREATE_SERVER(7)), IMPORT FOREIGN SCHEMA (IMPORT_FOREIGN_SCHEMA(7))
221PostgreSQL 11.6 2019 CREATE FOREIGN TABLE(7)