NAME¶

CREATE TABLE - define a new table

SYNOPSIS¶

CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } ] TABLE table_name ( [


  { column_name data_type [ DEFAULT default_expr ] [ column_constraint [ ... ] ]


    | table_constraint


    | LIKE parent_table [ { INCLUDING | EXCLUDING } { DEFAULTS | CONSTRAINTS | INDEXES } ] ... }


    [, ... ]
] )
[ INHERITS ( parent_table [, ... ] ) ]
[ WITH ( storage_parameter [= value] [, ... ] ) | WITH OIDS | WITHOUT OIDS ]
[ ON COMMIT { PRESERVE ROWS | DELETE ROWS | DROP } ]
[ TABLESPACE tablespace ]
where column_constraint is:
[ CONSTRAINT constraint_name ]
{ NOT NULL | 


  NULL | 


  UNIQUE index_parameters |


  PRIMARY KEY index_parameters |


  CHECK ( expression ) |


  REFERENCES reftable [ ( refcolumn ) ] [ MATCH FULL | MATCH PARTIAL | MATCH SIMPLE ]


    [ ON DELETE action ] [ ON UPDATE action ] }
[ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]
and table_constraint is:
[ CONSTRAINT constraint_name ]
{ UNIQUE ( column_name [, ... ] ) index_parameters |


  PRIMARY KEY ( column_name [, ... ] ) index_parameters |


  CHECK ( expression ) |


  FOREIGN KEY ( column_name [, ... ] ) REFERENCES reftable [ ( refcolumn [, ... ] ) ]


    [ MATCH FULL | MATCH PARTIAL | MATCH SIMPLE ] [ ON DELETE action ] [ ON UPDATE action ] }
[ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]
index_parameters in UNIQUE and PRIMARY KEY constraints are:
[ WITH ( storage_parameter [= value] [, ... ] ) ]
[ USING INDEX TABLESPACE tablespace ]

DESCRIPTION¶

CREATE TABLE will create a new, initially empty table in the current database. The table will be owned by the user issuing the command.

If a schema name is given (for example, CREATE TABLE myschema.mytable ...) then the table is created in the specified schema. Otherwise it is created in the current schema. Temporary tables exist in a special schema, so a schema name cannot be given when creating a temporary table. The name of the table must be distinct from the name of any other table, sequence, index, or view in the same schema.

CREATE TABLE also automatically creates a data type that represents the composite type corresponding to one row of the table. Therefore, tables cannot have the same name as any existing data type in the same schema.

The optional constraint clauses specify constraints (tests) that new or updated rows must satisfy for an insert or update operation to succeed. A constraint is an SQL object that helps define the set of valid values in the table in various ways.

There are two ways to define constraints: table constraints and column constraints. A column constraint is defined as part of a column definition. A table constraint definition is not tied to a particular column, and it can encompass more than one column. Every column constraint can also be written as a table constraint; a column constraint is only a notational convenience for use when the constraint only affects one column.

PARAMETERS¶

TEMPORARY or TEMP

If specified, the table is created as a temporary table. Temporary tables are automatically dropped at the end of a session, or optionally at the end of the current transaction (see ON COMMIT below). Existing permanent tables with the same name are not visible to the current session while the temporary table exists, unless they are referenced with schema-qualified names. Any indexes created on a temporary table are automatically temporary as well.

Optionally, GLOBAL or LOCAL can be written before TEMPORARY or TEMP. This makes no difference in PostgreSQL, but see Compatibility [create_table(7)].

table_name

The name (optionally schema-qualified) of the table to be created.

column_name

The name of a column to be created in the new table.

data_type

The data type of the column. This can include array specifiers. For more information on the data types supported by PostgreSQL, refer to in the documentation.

DEFAULT

The DEFAULT clause assigns a default data value for the column whose column definition it appears within. The value is any variable-free expression (subqueries and cross-references to other columns in the current table are not allowed). The data type of the default expression must match the data type of the column.

The default expression will be used in any insert operation that does not specify a value for the column. If there is no default for a column, then the default is null.

INHERITS ( parent_table [, ... ] )

The optional INHERITS clause specifies a list of tables from which the new table automatically inherits all columns.

Use of INHERITS creates a persistent relationship between the new child table and its parent table(s). Schema modifications to the parent(s) normally propagate to children as well, and by default the data of the child table is included in scans of the parent(s).

If the same column name exists in more than one parent table, an error is reported unless the data types of the columns match in each of the parent tables. If there is no conflict, then the duplicate columns are merged to form a single column in the new table. If the column name list of the new table contains a column name that is also inherited, the data type must likewise match the inherited column(s), and the column definitions are merged into one. If the new table explicitly specifies a default value for the column, this default overrides any defaults from inherited declarations of the column. Otherwise, any parents that specify default values for the column must all specify the same default, or an error will be reported.

CHECK constraints are merged in essentially the same way as columns: if multiple parent tables and/or the new table definition contain identically-named CHECK constraints, these constraints must all have the same check expression, or an error will be reported. Constraints having the same name and expression will be merged into one copy. Notice that an unnamed CHECK constraint in the new table will never be merged, since a unique name will always be chosen for it.

LIKE parent_table [ { INCLUDING | EXCLUDING } { DEFAULTS | CONSTRAINTS | INDEXES } ]

The LIKE clause specifies a table from which the new table automatically copies all column names, their data types, and their not-null constraints.

Unlike INHERITS, the new table and original table are completely decoupled after creation is complete. Changes to the original table will not be applied to the new table, and it is not possible to include data of the new table in scans of the original table.

Default expressions for the copied column definitions will only be copied if INCLUDING DEFAULTS is specified. The default behavior is to exclude default expressions, resulting in the copied columns in the new table having null defaults.

Not-null constraints are always copied to the new table. CHECK constraints will only be copied if INCLUDING CONSTRAINTS is specified; other types of constraints will never be copied. Also, no distinction is made between column constraints and table constraints — when constraints are requested, all check constraints are copied.

Any indexes on the original table will not be created on the new table, unless the INCLUDING INDEXES clause is specified.

Note also that unlike INHERITS, copied columns and constraints are not merged with similarly named columns and constraints. If the same name is specified explicitly or in another LIKE clause, an error is signalled.

CONSTRAINT constraint_name

An optional name for a column or table constraint. If the constraint is violated, the constraint name is present in error messages, so constraint names like col must be positive can be used to communicate helpful constraint information to client applications. (Double-quotes are needed to specify constraint names that contain spaces.) If a constraint name is not specified, the system generates a name.

NOT NULL

The column is not allowed to contain null values.

NULL

The column is allowed to contain null values. This is the default.

This clause is only provided for compatibility with non-standard SQL databases. Its use is discouraged in new applications.

UNIQUE (column constraint)

UNIQUE ( column_name [, ... ] ) (table constraint)

The UNIQUE constraint specifies that a group of one or more columns of a table can contain only unique values. The behavior of the unique table constraint is the same as that for column constraints, with the additional capability to span multiple columns.

For the purpose of a unique constraint, null values are not considered equal.

Each unique table constraint must name a set of columns that is different from the set of columns named by any other unique or primary key constraint defined for the table. (Otherwise it would just be the same constraint listed twice.)

PRIMARY KEY (column constraint)

PRIMARY KEY ( column_name [, ... ] ) (table constraint)

The primary key constraint specifies that a column or columns of a table can contain only unique (non-duplicate), nonnull values. Technically, PRIMARY KEY is merely a combination of UNIQUE and NOT NULL, but identifying a set of columns as primary key also provides metadata about the design of the schema, as a primary key implies that other tables can rely on this set of columns as a unique identifier for rows.

Only one primary key can be specified for a table, whether as a column constraint or a table constraint.

The primary key constraint should name a set of columns that is different from other sets of columns named by any unique constraint defined for the same table.

CHECK ( expression )

The CHECK clause specifies an expression producing a Boolean result which new or updated rows must satisfy for an insert or update operation to succeed. Expressions evaluating to TRUE or UNKNOWN succeed. Should any row of an insert or update operation produce a FALSE result an error exception is raised and the insert or update does not alter the database. A check constraint specified as a column constraint should reference that column's value only, while an expression appearing in a table constraint can reference multiple columns.

Currently, CHECK expressions cannot contain subqueries nor refer to variables other than columns of the current row.

REFERENCES reftable [ ( refcolumn ) ] [ MATCH matchtype ] [ ON DELETE action ] [ ON UPDATE action ] (column constraint)

FOREIGN KEY ( column [, ... ] )

These clauses specify a foreign key constraint, which requires that a group of one or more columns of the new table must only contain values that match values in the referenced column(s) of some row of the referenced table. If refcolumn is omitted, the primary key of the reftable is used. The referenced columns must be the columns of a unique or primary key constraint in the referenced table. Note that foreign key constraints cannot be defined between temporary tables and permanent tables.

A value inserted into the referencing column(s) is matched against the values of the referenced table and referenced columns using the given match type. There are three match types: MATCH FULL, MATCH PARTIAL, and MATCH SIMPLE, which is also the default. MATCH FULL will not allow one column of a multicolumn foreign key to be null unless all foreign key columns are null. MATCH SIMPLE allows some foreign key columns to be null while other parts of the foreign key are not null. MATCH PARTIAL is not yet implemented.

In addition, when the data in the referenced columns is changed, certain actions are performed on the data in this table's columns. The ON DELETE clause specifies the action to perform when a referenced row in the referenced table is being deleted. Likewise, the ON UPDATE clause specifies the action to perform when a referenced column in the referenced table is being updated to a new value. If the row is updated, but the referenced column is not actually changed, no action is done. Referential actions other than the NO ACTION check cannot be deferred, even if the constraint is declared deferrable. There are the following possible actions for each clause:

If the referenced column(s) are changed frequently, it might be wise to add an index to the foreign key column so that referential actions associated with the foreign key column can be performed more efficiently.

DEFERRABLE

NOT DEFERRABLE

This controls whether the constraint can be deferred. A constraint that is not deferrable will be checked immediately after every command. Checking of constraints that are deferrable can be postponed until the end of the transaction (using the SET CONSTRAINTS [set_constraints(7)] command). NOT DEFERRABLE is the default. Only foreign key constraints currently accept this clause. All other constraint types are not deferrable.

INITIALLY IMMEDIATE

INITIALLY DEFERRED

If a constraint is deferrable, this clause specifies the default time to check the constraint. If the constraint is INITIALLY IMMEDIATE, it is checked after each statement. This is the default. If the constraint is INITIALLY DEFERRED, it is checked only at the end of the transaction. The constraint check time can be altered with the SET CONSTRAINTS [set_constraints(7)] command.

WITH ( storage_parameter [= value] [, ... ] )

This clause specifies optional storage parameters for a table or index; see Storage Parameters [create_table(7)] for more information. The WITH clause for a table can also include OIDS=TRUE (or just OIDS) to specify that rows of the new table should have OIDs (object identifiers) assigned to them, or OIDS=FALSE to specify that the rows should not have OIDs. If OIDS is not specified, the default setting depends upon the default_with_oids configuration parameter. (If the new table inherits from any tables that have OIDs, then OIDS=TRUE is forced even if the command says OIDS=FALSE.)

If OIDS=FALSE is specified or implied, the new table does not store OIDs and no OID will be assigned for a row inserted into it. This is generally considered worthwhile, since it will reduce OID consumption and thereby postpone the wraparound of the 32-bit OID counter. Once the counter wraps around, OIDs can no longer be assumed to be unique, which makes them considerably less useful. In addition, excluding OIDs from a table reduces the space required to store the table on disk by 4 bytes per row (on most machines), slightly improving performance.

To remove OIDs from a table after it has been created, use ALTER TABLE [alter_table(7)].

WITH OIDS

WITHOUT OIDS

These are obsolescent syntaxes equivalent to WITH (OIDS) and WITH (OIDS=FALSE), respectively. If you wish to give both an OIDS setting and storage parameters, you must use the WITH ( ... ) syntax; see above.

ON COMMIT

The behavior of temporary tables at the end of a transaction block can be controlled using ON COMMIT. The three options are:

TABLESPACE tablespace

The tablespace is the name of the tablespace in which the new table is to be created. If not specified, default_tablespace is consulted, or temp_tablespaces if the table is temporary.

USING INDEX TABLESPACE tablespace

This clause allows selection of the tablespace in which the index associated with a UNIQUE or PRIMARY KEY constraint will be created. If not specified, default_tablespace is consulted, or temp_tablespaces if the table is temporary.

NOTES¶

Using OIDs in new applications is not recommended: where possible, using a SERIAL or other sequence generator as the table's primary key is preferred. However, if your application does make use of OIDs to identify specific rows of a table, it is recommended to create a unique constraint on the oid column of that table, to ensure that OIDs in the table will indeed uniquely identify rows even after counter wraparound. Avoid assuming that OIDs are unique across tables; if you need a database-wide unique identifier, use the combination of tableoid and row OID for the purpose.

PostgreSQL automatically creates an index for each unique constraint and primary key constraint to enforce uniqueness. Thus, it is not necessary to create an index explicitly for primary key columns. (See CREATE INDEX [create_index(7)] for more information.)

Unique constraints and primary keys are not inherited in the current implementation. This makes the combination of inheritance and unique constraints rather dysfunctional.

A table cannot have more than 1600 columns. (In practice, the effective limit is usually lower because of tuple-length constraints.)

EXAMPLES¶

Create table films and table distributors:

CREATE TABLE films (


    code        char(5) CONSTRAINT firstkey PRIMARY KEY,


    title       varchar(40) NOT NULL,


    did         integer NOT NULL,


    date_prod   date,


    kind        varchar(10),


    len         interval hour to minute
);

CREATE TABLE distributors (


     did    integer PRIMARY KEY DEFAULT nextval('serial'),


     name   varchar(40) NOT NULL CHECK (name <> '')
);

Create a table with a 2-dimensional array:

CREATE TABLE array_int (


    vector  int[][]
);

Define a unique table constraint for the table films. Unique table constraints can be defined on one or more columns of the table:

CREATE TABLE films (


    code        char(5),


    title       varchar(40),


    did         integer,


    date_prod   date,


    kind        varchar(10),


    len         interval hour to minute,


    CONSTRAINT production UNIQUE(date_prod)
);

Define a check column constraint:

CREATE TABLE distributors (


    did     integer CHECK (did > 100),


    name    varchar(40)
);

Define a check table constraint:

CREATE TABLE distributors (


    did     integer,


    name    varchar(40)


    CONSTRAINT con1 CHECK (did > 100 AND name <> '')
);

Define a primary key table constraint for the table films:

CREATE TABLE films (


    code        char(5),


    title       varchar(40),


    did         integer,


    date_prod   date,


    kind        varchar(10),


    len         interval hour to minute,


    CONSTRAINT code_title PRIMARY KEY(code,title)
);

Define a primary key constraint for table distributors. The following two examples are equivalent, the first using the table constraint syntax, the second the column constraint syntax:

CREATE TABLE distributors (


    did     integer,


    name    varchar(40),


    PRIMARY KEY(did)
);

CREATE TABLE distributors (


    did     integer PRIMARY KEY,


    name    varchar(40)
);

Assign a literal constant default value for the column name, arrange for the default value of column did to be generated by selecting the next value of a sequence object, and make the default value of modtime be the time at which the row is inserted:

CREATE TABLE distributors (


    name      varchar(40) DEFAULT 'Luso Films',


    did       integer DEFAULT nextval('distributors_serial'),


    modtime   timestamp DEFAULT current_timestamp
);

Define two NOT NULL column constraints on the table distributors, one of which is explicitly given a name:

CREATE TABLE distributors (


    did     integer CONSTRAINT no_null NOT NULL,


    name    varchar(40) NOT NULL
);

Define a unique constraint for the name column:

CREATE TABLE distributors (


    did     integer,


    name    varchar(40) UNIQUE
);

CREATE TABLE distributors (


    did     integer,


    name    varchar(40),


    UNIQUE(name)
);

Create the same table, specifying 70% fill factor for both the table and its unique index:

CREATE TABLE distributors (


    did     integer,


    name    varchar(40),


    UNIQUE(name) WITH (fillfactor=70)
)
WITH (fillfactor=70);

Create table cinemas in tablespace diskvol1:

CREATE TABLE cinemas (


        id serial,


        name text,


        location text
) TABLESPACE diskvol1;

COMPATIBILITY¶

The CREATE TABLE command conforms to the SQL standard, with exceptions listed below.

SEE ALSO¶

ALTER TABLE [alter_table(7)], DROP TABLE [drop_table(7)], CREATE TABLESPACE [create_tablespace(7)]