CREATE TABLE SQL - Language Statements CREATE TABLE Creates a new table 1998-04-15 CREATE TABLE table ( column type [DEFAULT value] [CONSTRAINT column_constraint] [, ...] [, column ...] [, CONSTRAINT table_constraint] ) [INHERITS ( inherited_table [, ...] )] 1998-04-15 table The name of a new table to be created. column The name of a column. type The type of the column. (Refer to the Postgres User's Guide for further information about data types). value A default value for a column. See the DEFAULT clause for more information. inherited_table The optional INHERITS clause specifies a collection of table names from which this table automatically inherits all fields. If any inherited field name appears more than once, PostgreSQL reports an error. PostgreSQL automatically allows the created table to inherit functions on tables above it in the inheritance hierarchy. Inheritance of functions is done according to the conventions of the Common Lisp Object System (CLOS). column_constraint table_constraint The optional CONSTRAINT clause specifies a list of integrity constraints which new or updated entries must satisfy for an insert or update operation to succeed. Each constraint must evaluate to a boolean expression. Multiple columns may be referenced within a single constraint. See CONSTRAINT clause for more information. 1998-04-15 status 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: amcreate: "table" relation already exists which occurs at runtime, if the table specified already exists in the database. 1998-04-15 CREATE TABLE will enter a new table into the current data base. The table will be "owned" by the user issuing the command. The new table is created as a heap with no initial data. A table can have no more than 1600 columns (realistically, this is limited by the fact that tuple sizes must be less than 8192 bytes), but this limit may be configured lower at some sites. A table cannot have the same name as a system catalog table. 1998-04-15 DEFAULT value The DEFAULT clause assigns a default data value to a column. value The possible values for expression are: a literal value a user function a niladic function ERROR: DEFAULT: type mismatched if data type of default value doesn't match the column definition's data type. The DEFAULT clause assigns a default data value to a column (via a column definition in the CREATE TABLE statement). The data type of a default value must match the column definition's data type. An INSERT operation that includes a column without a specified default value will assign the NULL value to the column if no explicit data value is provided for it. Default literal means that the default is the specified constant value. Default niladic-function or user-function means that the default is the value of the specified function at the time of the INSERT. There are two types of niladic functions: niladic USER CURRENT_USER / USER See CURRENT_USER function SESSION_USER not yet supported SYSTEM_USER not yet supported niladic datetime CURRENT_DATE See CURRENT_DATE function CURRENT_TIME See CURRENT_TIME function CURRENT_TIMESTAMP See CURRENT_TIMESTAMP function 1998-04-15 [ CONSTRAINT name ] NOT NULL The NOT NULL constraint specifies a rule that a column may contain only non-null values. The NOT NULL constraint is a column constraint. name The optional name of a constraint. 1998-04-15 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. 1998-04-15 Table Constraint definition [ CONSTRAINT name ] UNIQUE ( column [, ...] ) Column Constraint definition [ CONSTRAINT name ] UNIQUE name An arbitrary name given to a constraint. column A name of a column in a table. 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. Each UNIQUE 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. PostgreSQL automatically creates a unique index for each UNIQUE constraint, to assure data integrity. See CREATE INDEX for more information. 1998-04-15 Table constraint definition [ CONSTRAINT name ] { PRIMARY KEY constraint | UNIQUE constraint | CHECK constraint } Column constraint definition [ CONSTRAINT name ] { NOT NULL constraint | PRIMARY KEY constraint | UNIQUE constraint | CHECK constraint } name An arbitrary name given to an integrity constraint. constraint The definition of the constraint. A Constraint is a named rule: a SQL object which helps define valid sets of values by putting limits on the results of INSERT, UPDATE or DELETE operations performed on a Base table. There are two ways to define integrity constraints: Table constraint and Column constraint. A Table Constraint is an integrity Constraint defined on one or more Columns of a Base table. The four variations of "Table Constraint" are: PRIMARY KEY FOREIGN KEY UNIQUE CHECK 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 PostgreSQL does not yet (at release 6.3.2) support the FOREIGN KEY or REFERENCES integrity constraints, although the parser will accept them. Foreign keys may be partially emulated by triggers (See CREATE TRIGGER statement) PostgreSQL does not yet support either DOMAINs or ASSERTIONs. 1998-04-15 [ CONSTRAINT name ] CHECK ( condition [, ...] ) name An arbitrary name given to a constraint. condition Any valid conditional expression. 1998-04-15 ERROR: ExecAppend: rejected due to CHECK constraint "table_column". 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 rule that a group of one or more columns of a table may contain only those values allowed by the rule. The CHECK constraint is either a table constraint or a column constraint. PostgreSQL automatically creates an unique index to assure data integrity. (See CREATE INDEX statement) The SQL92 CHECK column constraints can only be defined on, and refer to, one column of the table. PostgreSQL does not have this restriction. The following CHECK constraints gives a parse error like: ERROR: parser: parse error at or near "opname": CHECK ( column BETWEEN 'A' AND 'Z' ) CHECK ( column IN ('A','Z')) CHECK ( column NOT LIKE 'A%') 1998-04-15 Table constraint definition [ CONSTRAINT name ] PRIMARY KEY ( column [, ...] ) Column constraint definition [ CONSTRAINT name ] PRIMARY KEY name An arbitrary name for the constraint. column The name of a column in the table. 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, (not duplicates), 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. A table's set of valid values may be constrained by only one PRIMARY KEY constraint at a time. The PRIMARY KEY constraint must name a set of columns that is different from the set of columns named by any UNIQUE constraint defined for the same table. 1998-04-15 PostgreSQL automatically creates an unique index to assure data integrity. (See CREATE INDEX statement) 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(03) 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 two NOT NULL column constraints on the table distributors CREATE TABLE distributors ( did DECIMAL(3) CONSTRAINT no_null NOT NULL, name VARCHAR(40) NOT NULL ); 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(03), date_prod DATE, kind CHAR(10), len INTERVAL HOUR TO MINUTE, CONSTRAINT production UNIQUE(date_prod) ); Defines a UNIQUE column constraint for the table distributors. UNIQUE column constraints can only be defined on one column of the table (the following two examples are equivalents). CREATE TABLE distributors ( did DECIMAL(03), name VARCHAR(40) UNIQUE, UNIQUE(name) ); CREATE TABLE distributors ( did DECIMAL(3), name VARCHAR(40) UNIQUE ); 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(05), title VARCHAR(40), did DECIMAL(03), 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 equivalents) CREATE TABLE distributors ( did DECIMAL(03), name CHAR VARYING(40), PRIMARY KEY(did) ); CREATE TABLE distributors ( did DECIMAL(03) PRIMARY KEY, name VARCHAR(40) ); To assign a sequence as the default for the column did, and a literal to the column name CREATE TABLE distributors ( did DECIMAL(3) DEFAULT NEXTVAL('serial'), name VARCHAR(40) DEFAULT 'luso films' ); 1998-04-15 CREATE TABLE/INHERITS is a PostgreSQL language extension. 1998-04-15 In addition to normal CREATE TABLE, SQL92 also defines a CREATE TEMPORARY TABLE statement: CREATE [ {GLOBAL | LOCAL} ] TEMPORARY TABLE table ( column type [DEFAULT value] [CONSTRAINT column_constraint] [, ...] ) [CONSTRAINT table_constraint ] [ ON COMMIT {DELETE | PRESERVE} ROWS ] For temporary tables, the CREATE TEMPORARY TABLE statement names a new table 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, the default option, ON COMMIT DELETE ROWS, is assumed. To create a temporary table: CREATE TEMPORARY TABLE actors ( id DECIMAL(03), name VARCHAR(40), CONSTRAINT actor_id CHECK (id < 150) ) ON COMMIT DELETE ROWS Temporary tables are not currently available in Postgres. TIP: In the current release of Postgres (v6.3.2), to create a temporary table you must create and drop the table by explicit commands. 1998-04-15 SQL92 specifies some additional capabilities for UNIQUE: Table Constraint definition [ CONSTRAINT name ] UNIQUE ( column [, ...] ) [ {INITIALLY DEFERRED | INITIALLY IMMEDIATE} ] [ [ NOT ] DEFERRABLE ] Column Constraint definition [ CONSTRAINT name ] UNIQUE [ {INITIALLY DEFERRED | INITIALLY IMMEDIATE} ] [ [ NOT ] DEFERRABLE ] 1998-04-15 SQL92 specifies some additional capabilities for NOT NULL: [ CONSTRAINT name ] NOT NULL [ {INITIALLY DEFERRED | INITIALLY IMMEDIATE} ] [ [ NOT ] DEFERRABLE ] 1998-04-15 SQL92 specifies some additional capabilities for the DEFAULT clause. A DEFAULT clause is used to set the default value for a column or a domain. DEFAULT literal | niladic USER function | niladic datetime function | NULL 1998-04-15 SQL92 specifies some additional capabilities for CONSTRAINTs, it also defines assertions and domain constraints. An assertion is a special type of integrity constraint and share the same namespace as other constraints. However, an assertion is not necessarily dependent on one particular base 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 name ] CHECK constraint [ {INITIALLY DEFERRED | INITIALLY IMMEDIATE} ] [ [ NOT ] DEFERRABLE ] Table constraint definition: [ CONSTRAINT name ] { PRIMARY KEY constraint | FOREIGN KEY constraint | UNIQUE constraint | CHECK constraint } [ {INITIALLY DEFERRED | INITIALLY IMMEDIATE} ] [ [ NOT ] DEFERRABLE ] Column constraint definition: [ CONSTRAINT name ] { NOT NULL constraint | PRIMARY KEY constraint | FOREIGN KEY constraint | UNIQUE constraint | 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 means that the Constraint must be checked for violation of its rule after the execution of every SQL statement. DEFERRABLE means that checking of the Constraint may be deferred until some later time, but no later than the end of the current transaction. The constraint mode for every Constraint always has an initial default value which is set for that Constraint at the beginning of a transaction. INITIALLY IMMEDIATE means that, as of the start of the transaction, the Constraint must be checked for violation of its rule after the execution of every SQL statement. INITIALLY DEFERRED means that, as of the start of the transaction, checking of the Constraint may be deferred until some later time, but no later than the end of the current transaction. 1998-04-15 SQL92 specifies some additional capabilities for CHECK: A CHECK constraint is either a table constraint, a column constraint or a domain constraint. table constraint definition: [ CONSTRAINT name ] CHECK ( VALUE condition ) [ {INITIALLY DEFERRED | INITIALLY IMMEDIATE} ] [ [ NOT ] DEFERRABLE ] column constraint definition: [ CONSTRAINT name ] CHECK ( VALUE condition ) [ {INITIALLY DEFERRED | INITIALLY IMMEDIATE} ] [ [ NOT ] DEFERRABLE ] domain constraint definition: [ CONSTRAINT name ] CHECK ( VALUE condition ) [ {INITIALLY DEFERRED | INITIALLY IMMEDIATE} ] [ [ NOT ] DEFERRABLE ] CHECK domain constraints can be defined in either a CREATE DOMAIN statement or an ALTER DOMAIN statement: CREATE DOMAIN duration AS SMALLINT CONSTRAINT minutes CHECK (VALUE IN (90,120,180,240)); ALTER DOMAIN cities ADD CONSTRAINT new_city CHECK (VALUE LIKE 'L%'); 1998-04-15 SQL92 specifies some additional capabilities for PRIMARY KEY: Table Constraint definition: [ CONSTRAINT name ] PRIMARY KEY ( column [, ...] ) [ {INITIALLY DEFERRED | INITIALLY IMMEDIATE} ] [ [ NOT ] DEFERRABLE ] Column Constraint definition: [ CONSTRAINT name ] PRIMARY KEY [ {INITIALLY DEFERRED | INITIALLY IMMEDIATE} ] [ [ NOT ] DEFERRABLE ]