alter table\(em add attributes to a class

.nf

\fBaltertable\fR classname [*]

\fBaddcolumn\fR attname type

\fBaltertable\fR classname [ * ]

\fBadd\fR [\fBcolumn\fR ] attname type

.fi

.nf

\fBaltertable\fR classname [ * ]

\fBadd\fR\fB(\fR attname type\fB)\fR

.fi

.IR classname.

The new attributes and their types are specified

in the same style and with the the same restrictions as in

.IR createtable (l).

.IR"create table"(l).

.PP

In order to add an attribute to each class in an entire inheritance

hierarchy, use the

create table\(em create a new class

.nf

\fBcreatetable\fR classname\fB(\fPattname-1 type-1 {\fB,\fP attname-i type-i}\fB)\fP

[\fBinherits\fR\fB(\fR classname-1 {\fB,\fR classname-i}\fB)\fR]

\fBcreatetable\fR classname\fB(\fPattname type [\fBdefault\fP value] [\fB,\fP attname type\fBdefault\fP value]\fB)\fP

[\fBinherits\fR\fB(\fR classname [\fB,\fR classname]\fB)\fR]

[\fBconstraint\fR cname\fBcheck\fR\fB(\fR test\fB)\fR [\fB,\fR\fBcheck\fR test]

[\fBarchive\fR\fB=\fR archive_mode]

[\fBstore\fR\fB=\fR\*(lqsmgr_name\*(rq]

[\fBarch_store\fR\fB=\fR\*(lqsmgr_name\*(rq]

.fi

.BR"Createtable"

.BR"CreateTable"

will enter a new class into the current data base. The class will be

\*(lqowned\*(rq by the user issuing the command. The name of the

class is

.IR classname

and the attributes are as specified in the list of

.IR attnames.

The

.IR ith

attribute is created with the type specified by

.IR type"-i."

Each attribute is created with the type specified by

.IR type"."

Each type may be a simple type, a complex type (set) or an array type.

Each attribute may have a default value, specified by the

.IR default

clause which is the keyword "default" followed by a constant or expression.

.PP

Each array attribute stores arrays that must have the same number of

dimensions but may have different sizes and array index bounds. An

.nf

att_name type[][]..[]

.fi

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.

.PP

The optional

.BR inherits

.IR classname

is automatically created as a type. Therefore, one or more instances

from the class are automatically a type and can be used in

.IR altertable(l)

.IR"alter table"(l)

or other

.BR"create table"

statements. See

.IR pgintro(1)

for a further discussion of this point.

.PP

The optional

.BR 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.

.PP

The optional

.BR store

and

.BR arch_store

.fi

.nf

--

--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 <> '')

.fi

.nf

--

--Create class foo on magnetic disk and archive historical data

--

create table foo (bar int4) archive = heavy