GNU/Linux man pages
Livre :
Expressions régulières,
Syntaxe et mise en oeuvre :
GNU/Linux |
RedHat 5.2(Apollo) |
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create_table(l) |
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create table - create a new class
create table classname (attname type [default value] [not null]
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[, attname type [default value] [not null] [, ...] ] ) | ||
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[inherits ( classname [, classname] )] | ||
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[constraint cname check ( test ) [, check ( test ) ] ] |
Create Table will enter a new class into the current data base. The class will be “owned” by the user issuing the command. The name of the class is classname and the attributes are as specified in the list of attnames. Each attribute is created with the type specified by type. 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 default clause which is the keyword "default" followed by a constant or expression.
Each array
attribute stores arrays that must have the same number of
dimensions but may have different sizes and array index
bounds. An array of dimension n is specified by
appending n pairs of square brackets:
att_name type[][]..[]
N.B. As of Postgres version 6.0, consistant array dimensions
within an attribute are not enforced. This will likely
change in a future release.
The optional inherits clause specifies a collection of class names from which this class automatically inherits all fields. If any inherited field name appears more than once, Postgres reports an error. Postgres automatically allows the created class to inherit functions on classes above it in the inheritance hierarchy. Inheritance of functions is done according to the conventions of the Common Lisp Object System (CLOS).
Each new class classname is automatically created as a type. Therefore, one or more instances from the class are automatically a type and can be used in alter table(l) or other create table statements. See pgintro(1) for a further discussion of this point.
The optional constraint clause specifies a list of constraints or tests which new or updated entries must satisfy for an insert or update operation to succeed. Each constraint must evaluate to a boolean expression. Multiple attributes may be referenced within a single constraint.
The new class is created as a heap with no initial data. A class can have no more than 1600 attributes (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 class cannot have the same name as a system catalog class.
--
-- Create class emp with attributes name, sal and bdate
--
create table emp (name char16, salary float4, bdate abstime)
--
--Create class permemp with pension information that
--inherits all fields of emp
--
create table permemp (plan char16) inherits (emp)
--
--Create class emppay with attributes name and wage with
--a default salary and constraints on wage range
--
create table emppay (name text not null, wage float4 default
10.00)
constraint empcon check (wage > 5.30 and wage <=
30.00), check (name <> ’’)
--
--Create class tictactoe to store noughts-and-crosses
--boards as a 2-dimensional array
--
create table tictactoe (game int4, board char[][])
--
--Create a class newemp with a set attribute
"manager". A
--set (complex) attribute may be of the same type as the
--relation being defined (as here) or of a different complex
--type. The type must exist in the "pg_type"
catalog or be
--the one currently being defined.
--
create table newemp (name text, manager newemp)
drop table(l).
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create_table(l) | |