CREATE TABLE SQL - Language Statements CREATE TABLE Creates a new table 2001-01-11 CREATE [ TEMPORARY | TEMP ] TABLE table_name ( { column_name type [ column_constraint [ ... ] ] | table_constraint } [, ... ] ) [ INHERITS ( parent_table [, ... ] ) ] where column_constraint can be: [ CONSTRAINT constraint_name ] { NOT NULL | NULL | UNIQUE | PRIMARY KEY | DEFAULT value | CHECK (condition) | REFERENCES table [ ( column ) ] [ MATCH FULL | MATCH PARTIAL ] [ ON DELETE action ] [ ON UPDATE action ] [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ] } and table_constraint can be: [ CONSTRAINT constraint_name ] { UNIQUE ( column_name [, ... ] ) | PRIMARY KEY ( column_name [, ... ] ) | CHECK ( condition ) | FOREIGN KEY ( column_name [, ... ] ) REFERENCES table [ ( column [, ... ] ) ] [ MATCH FULL | MATCH PARTIAL ] [ ON DELETE action ] [ ON UPDATE action ] [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ] } TEMPORARY or TEMP If specified, the table is created only for this session, and is automatically dropped on session exit. Existing permanent tables with the same name are not visible (in this session) while the temporary table exists. Any indexes created on a temporary table are automatically temporary as well. table_name The name of the new table to be created. column_name The name of a column to be created in the new table. type The type of the column. This may include array specifiers. Refer to the PostgreSQL User's Guide for further information about data types and arrays. parent_table The optional INHERITS clause specifies a list of table names from which this table automatically inherits all fields. constraint_name An optional name for a column or table constraint. If not specified, the system generates a name. value A default value for a column. See the DEFAULT clause for more information. condition CHECK clauses specify integrity constraints or tests which new or updated rows must satisfy for an insert or update operation to succeed. Each constraint must be an expression producing a boolean result. A condition appearing within a column definition should reference that column's value only, while a condition appearing as a table constraint may reference multiple columns. table The name of an existing table to be referenced by a foreign key constraint. column The name of a column in an existing table to be referenced by a foreign key constraint. If not specified, the primary key of the existing table is assumed. action A keyword indicating the action to take when a foreign key constraint is violated. CREATE Message returned if table is successfully created. ERROR Message returned if table creation failed. This is usually accompanied by some descriptive text, such as: ERROR: Relation 'table' already exists , which occurs at runtime if the table specified already exists in the database. CREATE TABLE will enter a new, initially empty table into the current database. The table will be "owned" by the user issuing the command. Each type may be a simple type, a complex type (set) or an array type. Each attribute may be specified to be non-null and each may have a default value, specified by the . Consistent array dimensions within an attribute are not enforced. This will likely change in a future release. CREATE TABLE also automatically creates a data type that represents the tuple type (structure type) corresponding to one row of the table. Therefore, tables can't have the same name as any existing datatype. A table can have no more than 1600 columns (in practice, the effective limit is lower because of tuple-length constraints). A table cannot have the same name as a system catalog table. INHERITS ( parent_table [, ... ] ) The optional INHERITS clause specifies a list of table names from which the new table automatically inherits all fields. If the same field name appears in more than one parent table, Postgres reports an error unless the field definitions match in each of the parent tables. If there is no definition conflict, then the duplicate fields are merged to form a single field of the new table. If the new table's own field list contains a field name that is also inherited, this declaration must likewise match the inherited field(s), and the field definitions are merged into one. Inherited and new field declarations of the same name must specify exactly the same data type to avoid an error. They need not specify identical constraints --- all constraints provided from any declaration are merged together and all are applied to the new table. If the new table explicitly specifies a default value for the field, this default overrides any defaults from inherited declarations of the field. Otherwise, any parents that specify default values for the field must all specify the same default, or an error will be reported. Postgres automatically allows the created table to inherit functions on tables above it in the inheritance hierarchy; that is, if we create table foo inheriting from bar, then functions that accept the tuple type bar can also be applied to instances of foo. (Currently, this works reliably for functions on the first or only parent table, but not so well for functions on additional parents.) DEFAULT value The DEFAULT clause assigns a default data value for the column whose column definition it appears within. The value is any variable-free expression (note that sub-selects and cross-references to other columns in the current table are not supported). The data type of a default value must match the column definition's data type. The DEFAULT expression will be used in any INSERT operation that does not specify a value for the column. If there is no DEFAULT clause, then the default is NULL. CREATE TABLE distributors ( name VARCHAR(40) DEFAULT 'luso films', did INTEGER DEFAULT NEXTVAL('distributors_serial'), modtime TIMESTAMP DEFAULT now() ); The above assigns a literal constant default value for the column name, and arranges for the default value of column did to be generated by selecting the next value of a sequence object. The default value of modtime will be the time at which the row is inserted. It is worth remarking that modtime TIMESTAMP DEFAULT 'now' would produce a result that is probably not the intended one: the string 'now' will be coerced to a timestamp value immediately, and so the default value of modtime will always be the time of table creation. This difficulty is avoided by specifying the default value as a function call. [ CONSTRAINT constraint_name ] { NULL | NOT NULL | UNIQUE | PRIMARY KEY | CHECK condition | REFERENCES reftable [ ( refcolumn ) ] [ MATCH matchtype ] [ ON DELETE action ] [ ON UPDATE action ] [ [ NOT ] DEFERRABLE ] [ INITIALLY checktime ] } constraint_name An arbitrary name given to a constraint clause. NULL The column is allowed to contain NULL values. This is the default. NOT NULL The column is not allowed to contain NULL values. This is equivalent to the column constraint CHECK (column NOT NULL). UNIQUE The column must have unique values. In Postgres this is enforced by automatic creation of a unique index on the column. PRIMARY KEY This column is a primary key, which implies that other tables may rely on this column as a unique identifier for rows. Both UNIQUE and NOT NULL are implied by PRIMARY KEY. See PRIMARY KEY for more information. condition An arbitrary boolean-valued constraint condition. The optional constraint clauses specify constraints or tests which new or updated rows must satisfy for an insert or update operation to succeed. A constraint is a named rule: an SQL object which helps define valid sets of values by putting limits on the results of INSERT, UPDATE or DELETE operations performed on a table. There are two ways to define integrity constraints: table constraints, covered later, and column constraints, covered here. A column constraint is an integrity constraint defined as part of a column definition, and logically becomes a table constraint as soon as it is created. The column constraints available are: PRIMARY KEY REFERENCES UNIQUE CHECK NOT NULL [ CONSTRAINT name ] NOT NULL The NOT NULL constraint specifies a rule that a column may contain only non-null values. This is a column constraint only, and not allowed as a table constraint. status ERROR: ExecAppend: Fail to add null value in not null attribute "column". This error occurs at runtime if one tries to insert a null value into a column which has a NOT NULL constraint. Define two NOT NULL column constraints on the table distributors, one of which is explicitly given a name: CREATE TABLE distributors ( did DECIMAL(3) CONSTRAINT no_null NOT NULL, name VARCHAR(40) NOT NULL ); [ CONSTRAINT constraint_name ] UNIQUE constraint_name An arbitrary name given to a constraint clause. status ERROR: Cannot insert a duplicate key into a unique index. This error occurs at runtime if one tries to insert a duplicate value into a column. The UNIQUE constraint specifies a rule that a group of one or more distinct columns of a table may contain only unique values. The column definitions of the specified columns do not have to include a NOT NULL constraint to be included in a UNIQUE constraint. Having more than one null value in a column without a NOT NULL constraint, does not violate a UNIQUE constraint. (This deviates from the SQL92 definition, but is a more sensible convention. See the section on compatibility for more details.) Each UNIQUE column constraint must name a column that is different from the set of columns named by any other UNIQUE or PRIMARY KEY constraint defined for the table. Postgres automatically creates a unique index for each UNIQUE constraint, to assure data integrity. See CREATE INDEX for more information. Defines a UNIQUE constraint for the name column: CREATE TABLE distributors ( did DECIMAL(3), name VARCHAR(40) UNIQUE ); which is equivalent to the following specified as a table constraint: CREATE TABLE distributors ( did DECIMAL(3), name VARCHAR(40), UNIQUE(name) ); [ CONSTRAINT constraint_name ] CHECK ( condition ) constraint_name An arbitrary name given to a constraint clause. condition Any valid conditional expression evaluating to a boolean result. status ERROR: ExecAppend: rejected due to CHECK constraint "constraint_name". This error occurs at runtime if one tries to insert an illegal value into a column subject to a CHECK constraint. The CHECK constraint specifies a generic restriction on allowed values within a column. The CHECK constraint is also allowed as a table constraint. CHECK specifies a general boolean expression involving one or more columns of a table. A new row will be rejected if the boolean expression evaluates to FALSE when applied to the row's values. Currently, CHECK expressions cannot contain sub-selects nor refer to variables other than fields of the current row. The SQL92 standard says that CHECK column constraints may only refer to the column they apply to; only CHECK table constraints may refer to multiple columns. Postgres does not enforce this restriction. It treats column and table CHECK constraints alike. [ CONSTRAINT constraint_name ] PRIMARY KEY constraint_name An arbitrary name given to a constraint clause. ERROR: Cannot insert a duplicate key into a unique index. This occurs at runtime if one tries to insert a duplicate value into a column subject to a PRIMARY KEY constraint. The PRIMARY KEY column constraint specifies that a column of a table may contain only unique (non-duplicate), non-NULL values. The definition of the specified column does not have to include an explicit NOT NULL constraint to be included in a PRIMARY KEY constraint. Only one PRIMARY KEY can be specified for a table, whether as a column constraint or a table constraint. Postgres automatically creates a unique index to assure data integrity (see CREATE INDEX statement). 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, since it will result in duplication of equivalent indexes and unproductive additional runtime overhead. However, Postgres does not specifically disallow this. 2000-02-04 [ CONSTRAINT constraint_name ] REFERENCES reftable [ ( refcolumn ) ] [ MATCH matchtype ] [ ON DELETE action ] [ ON UPDATE action ] [ [ NOT ] DEFERRABLE ] [ INITIALLY checktime ] The REFERENCES constraint specifies a rule that a column value is checked against the values of another column. REFERENCES can also be specified as part of a FOREIGN KEY table constraint. constraint_name An arbitrary name given to a constraint clause. reftable The table that contains the data to check against. refcolumn The column in reftable to check the data against. If this is not specified, the PRIMARY KEY of the reftable is used. MATCH matchtype There are three match types: MATCH FULL, MATCH PARTIAL, and a default match type if none is specified. MATCH FULL will not allow one column of a multi-column foreign key to be NULL unless all foreign key columns are NULL. The default MATCH type allows some foreign key columns to be NULL while other parts of the foreign key are not NULL. MATCH PARTIAL is currently not supported. ON DELETE action The action to do when a referenced row in the referenced table is being deleted. There are the following actions. NO ACTION Produce error if foreign key violated. This is the default. RESTRICT Same as NO ACTION. CASCADE Delete any rows referencing the deleted row. SET NULL Set the referencing column values to NULL. SET DEFAULT Set the referencing column values to their default value. ON UPDATE action The action to do 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 changed, no action is done. There are the following actions. NO ACTION Produce error if foreign key violated. This is the default. RESTRICT Same as NO ACTION. CASCADE Update the value of the referencing column to the new value of the referenced column. SET NULL Set the referencing column values to NULL. SET DEFAULT Set the referencing column values to their default value. [ NOT ] DEFERRABLE This controls whether the constraint can be deferred to the end of the transaction. If DEFERRABLE, SET CONSTRAINTS ALL DEFERRED will cause the foreign key to be checked only at the end of the transaction. NOT DEFERRABLE is the default. INITIALLY checktime checktime has two possible values which specify the default time to check the constraint. DEFERRED Check constraint only at the end of the transaction. IMMEDIATE Check constraint after each statement. This is the default. 2000-02-04 status ERROR: name referential integrity violation - key referenced from table not found in reftable This error occurs at runtime if one tries to insert a value into a column which does not have a matching column in the referenced table. The REFERENCES column constraint specifies that a column of a table must only contain values which match against values in a referenced column of a referenced table. A value added to this column is matched against the values of the referenced table and referenced column using the given match type. In addition, when the referenced column data is changed, actions are run upon this column's matching data. 1998-09-11 Currently Postgres only supports MATCH FULL and a default match type. In addition, the referenced columns are supposed to be the columns of a UNIQUE constraint in the referenced table, however Postgres does not enforce this. [ CONSTRAINT name ] { PRIMARY KEY | UNIQUE } ( column [, ... ] ) [ CONSTRAINT name ] CHECK ( constraint ) [ CONSTRAINT name ] FOREIGN KEY ( column [, ... ] ) REFERENCES reftable [ ( refcolumn [, ... ] ) ] [ MATCH matchtype ] [ ON DELETE action ] [ ON UPDATE action ] [ [ NOT ] DEFERRABLE ] [ INITIALLY checktime ] constraint_name An arbitrary name given to a constraint clause. column [, ... ] The column name(s) for which to define a unique index and, for PRIMARY KEY, a NOT NULL constraint. CHECK ( constraint ) A boolean expression to be evaluated as the constraint. The possible outputs for the table constraint clause are the same as for the corresponding portions of the column constraint clause. A table constraint is an integrity constraint defined on one or more columns of a table. The four variations of "Table Constraint" are: UNIQUE CHECK PRIMARY KEY FOREIGN KEY [ CONSTRAINT constraint_name ] UNIQUE ( column [, ... ] ) constraint_name An arbitrary name given to a constraint clause. column A name of a column in a table. status ERROR: Cannot insert a duplicate key into a unique index This error occurs at runtime if one tries to insert a duplicate value into a column. The UNIQUE constraint specifies a rule that a group of one or more distinct columns of a table may 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. See the section on the UNIQUE column constraint for more details. Prevent duplicate rows in the table distributors: CREATE TABLE distributors ( did DECIMAL(3), name VARCHAR(40), UNIQUE(did,name) ); [ CONSTRAINT constraint_name ] PRIMARY KEY ( column [, ... ] ) constraint_name An arbitrary name given to a constraint clause. column [, ... ] The names of one or more columns in the table. status ERROR: Cannot insert a duplicate key into a unique index. This occurs at run-time if one tries to insert a duplicate value into a column subject to a PRIMARY KEY constraint. The PRIMARY KEY constraint specifies a rule that a group of one or more distinct columns of a table may contain only unique (nonduplicate), non-null values. The column definitions of the specified columns do not have to include a NOT NULL constraint to be included in a PRIMARY KEY constraint. The PRIMARY KEY table constraint is similar to that for column constraints, with the additional capability of encompassing multiple columns. Refer to the section on the PRIMARY KEY column constraint for more information. 2000-02-04 [ CONSTRAINT constraint_name ] FOREIGN KEY ( column [, ... ] ) REFERENCES reftable [ ( refcolumn [, ... ] ) ] [ MATCH matchtype ] [ ON DELETE action ] [ ON UPDATE action ] [ [ NOT ] DEFERRABLE ] [ INITIALLY checktime ] The REFERENCES constraint specifies a rule that a column value or set of column values is checked against the values in another table. constraint_name An arbitrary name given to a constraint clause. column [, ... ] The names of one or more columns in the table. reftable The table that contains the data to check against. referenced column [, ... ] One or more columns in the reftable to check the data against. If this is not specified, the PRIMARY KEY of the reftable is used. MATCH matchtype There are three match types: MATCH FULL, MATCH PARTIAL, and a default match type if none is specified. MATCH FULL will not allow one column of a multi-column foreign key to be NULL unless all foreign key columns are NULL. The default MATCH type allows some foreign key columns to be NULL while other parts of the foreign key are not NULL. MATCH PARTIAL is currently not supported. ON DELETE action The action to do when a referenced row in the referenced table is being deleted. There are the following actions. NO ACTION Produce error if foreign key violated. This is the default. RESTRICT Same as NO ACTION. CASCADE Delete any rows referencing the deleted row. SET NULL Set the referencing column values to NULL. SET DEFAULT Set the referencing column values to their default value. ON UPDATE action The action to do 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 changed, no action is done. There are the following actions. NO ACTION Produce error if foreign key violated. This is the default. RESTRICT Disallow update of row being referenced. CASCADE Update the value of the referencing column to the new value of the referenced column. SET NULL Set the referencing column values to NULL. SET DEFAULT Set the referencing column values to their default value. [ NOT ] DEFERRABLE This controls whether the constraint can be deferred to the end of the transaction. If DEFERRABLE, SET CONSTRAINTS ALL DEFERRED will cause the foreign key to be checked only at the end of the transaction. NOT DEFERRABLE is the default. INITIALLY checktime checktime has two possible values which specify the default time to check the constraint. IMMEDIATE Check constraint after each statement. This is the default. DEFERRED Check constraint only at the end of the transaction. 2000-02-04 status ERROR: name referential integrity violation - key referenced from table not found in reftable This error occurs at runtime if one tries to insert a value into a column which does not have a matching column in the referenced table. The FOREIGN KEY constraint specifies a rule that a group of one or more distinct columns of a table is related to a group of distinct columns in the referenced table. The FOREIGN KEY table constraint is similar to that for column constraints, with the additional capability of encompassing multiple columns. Refer to the section on the FOREIGN KEY column constraint for more information. Create table films and table distributors: CREATE TABLE films ( code CHARACTER(5) CONSTRAINT firstkey PRIMARY KEY, title CHARACTER VARYING(40) NOT NULL, did DECIMAL(3) NOT NULL, date_prod DATE, kind CHAR(10), len INTERVAL HOUR TO MINUTE ); CREATE TABLE distributors ( did DECIMAL(3) PRIMARY KEY DEFAULT NEXTVAL('serial'), name VARCHAR(40) NOT NULL CHECK (name <> '') ); Create a table with a 2-dimensional array: CREATE TABLE array ( 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 DECIMAL(3), date_prod DATE, kind CHAR(10), len INTERVAL HOUR TO MINUTE, CONSTRAINT production UNIQUE(date_prod) ); Define a CHECK column constraint: CREATE TABLE distributors ( did DECIMAL(3) CHECK (did > 100), name VARCHAR(40) ); Define a CHECK table constraint: CREATE TABLE distributors ( did DECIMAL(3), name VARCHAR(40) CONSTRAINT con1 CHECK (did > 100 AND name > '') ); Define a PRIMARY KEY table constraint for the table films. PRIMARY KEY table constraints can be defined on one or more columns of the table: CREATE TABLE films ( code CHAR(5), title VARCHAR(40), did DECIMAL(3), date_prod DATE, kind CHAR(10), len INTERVAL HOUR TO MINUTE, CONSTRAINT code_title PRIMARY KEY(code,title) ); Defines a PRIMARY KEY column constraint for table distributors. PRIMARY KEY column constraints can only be defined on one column of the table (the following two examples are equivalent): CREATE TABLE distributors ( did DECIMAL(3), name CHAR VARYING(40), PRIMARY KEY(did) ); CREATE TABLE distributors ( did DECIMAL(3) PRIMARY KEY, name VARCHAR(40) ); In addition to the locally visible temporary table, SQL92 also defines a CREATE GLOBAL TEMPORARY TABLE statement, and optionally an ON COMMIT clause: CREATE GLOBAL TEMPORARY TABLE table ( column type [ DEFAULT value ] [ CONSTRAINT column_constraint ] [, ... ] ) [ CONSTRAINT table_constraint ] [ ON COMMIT { DELETE | PRESERVE } ROWS ] For temporary tables, the CREATE GLOBAL TEMPORARY TABLE statement names a new table visible to other clients and defines the table's columns and constraints. The optional ON COMMIT clause of CREATE TEMPORARY TABLE specifies whether or not the temporary table should be emptied of rows whenever COMMIT is executed. If the ON COMMIT clause is omitted, SQL92 specifies that the default is ON COMMIT DELETE ROWS. However, Postgres' behavior is always like ON COMMIT PRESERVE ROWS. SQL92 specifies some additional capabilities for UNIQUE: Table Constraint definition: [ CONSTRAINT constraint_name ] UNIQUE ( column [, ... ] ) [ { INITIALLY DEFERRED | INITIALLY IMMEDIATE } ] [ [ NOT ] DEFERRABLE ] Column Constraint definition: [ CONSTRAINT constraint_name ] UNIQUE [ {INITIALLY DEFERRED | INITIALLY IMMEDIATE} ] [ [ NOT ] DEFERRABLE ] The NULL "constraint" (actually a non-constraint) is a Postgres extension to SQL92 that is included for symmetry with the NOT NULL clause (and for compatibility with some other RDBMSes). Since it is the default for any column, its presence is simply noise. [ CONSTRAINT constraint_name ] NULL SQL92 specifies some additional capabilities for NOT NULL: [ CONSTRAINT constraint_name ] NOT NULL [ {INITIALLY DEFERRED | INITIALLY IMMEDIATE} ] [ [ NOT ] DEFERRABLE ] SQL92 specifies some additional capabilities for constraints, and also defines assertions and domain constraints. Postgres does not yet support either domains or assertions. An assertion is a special type of integrity constraint and shares the same namespace as other constraints. However, an assertion is not necessarily dependent on one particular table as constraints are, so SQL-92 provides the CREATE ASSERTION statement as an alternate method for defining a constraint: CREATE ASSERTION name CHECK ( condition ) Domain constraints are defined by CREATE DOMAIN or ALTER DOMAIN statements: Domain constraint: [ CONSTRAINT constraint_name ] CHECK constraint [ {INITIALLY DEFERRED | INITIALLY IMMEDIATE} ] [ [ NOT ] DEFERRABLE ] Table constraint definition: [ CONSTRAINT constraint_name ] { PRIMARY KEY ( column, ... ) | FOREIGN KEY constraint | UNIQUE constraint | CHECK constraint } [ {INITIALLY DEFERRED | INITIALLY IMMEDIATE} ] [ [ NOT ] DEFERRABLE ] Column constraint definition: [ CONSTRAINT constraint_name ] { NOT NULL | PRIMARY KEY | FOREIGN KEY constraint | UNIQUE | CHECK constraint } [ {INITIALLY DEFERRED | INITIALLY IMMEDIATE} ] [ [ NOT ] DEFERRABLE ] A CONSTRAINT definition may contain one deferment attribute clause and/or one initial constraint mode clause, in any order. NOT DEFERRABLE The constraint must be checked at the end of each statement. SET CONSTRAINTS ALL DEFERRED will have no effect on this type of constraint. DEFERRABLE This controls whether the constraint can be deferred to the end of the transaction. If SET CONSTRAINTS ALL DEFERRED is used or the constraint is set to INITIALLY DEFERRED, this will cause the foreign key to be checked only at the end of the transaction. SET CONSTRAINTS changes the foreign key constraint mode only for the current transaction. INITIALLY IMMEDIATE Check constraint after each statement. This is the default. INITIALLY DEFERRED Check constraint only at the end of the transaction. SQL92 specifies some additional capabilities for CHECK in either table or column constraints. table constraint definition: [ CONSTRAINT constraint_name ] CHECK ( VALUE condition ) [ {INITIALLY DEFERRED | INITIALLY IMMEDIATE} ] [ [ NOT ] DEFERRABLE ] column constraint definition: [ CONSTRAINT constraint_name ] CHECK ( VALUE condition ) [ {INITIALLY DEFERRED | INITIALLY IMMEDIATE} ] [ [ NOT ] DEFERRABLE ] SQL92 specifies some additional capabilities for PRIMARY KEY: Table Constraint definition: [ CONSTRAINT constraint_name ] PRIMARY KEY ( column [, ... ] ) [ {INITIALLY DEFERRED | INITIALLY IMMEDIATE} ] [ [ NOT ] DEFERRABLE ] Column Constraint definition: [ CONSTRAINT constraint_name ] PRIMARY KEY [ {INITIALLY DEFERRED | INITIALLY IMMEDIATE} ] [ [ NOT ] DEFERRABLE ] Multiple inheritance via the INHERITS clause is a Postgres language extension. SQL99 (but not SQL92) defines single inheritance using a different syntax and different semantics. SQL99-style inheritance is not yet supported by Postgres.