diff options
| author | Marc G. Fournier | 1996-08-18 22:14:33 +0000 |
|---|---|---|
| committer | Marc G. Fournier | 1996-08-18 22:14:33 +0000 |
| commit | 69b655f481c0696064466bcee8e09c7844aff382 (patch) | |
| tree | 07c9f640637884cdded35df571ae6d03f6674d18 /doc/man/alter_table.l | |
Support Docs & ContribPG95-DIST
Diffstat (limited to 'doc/man/alter_table.l')
| -rw-r--r-- | doc/man/alter_table.l | 61 |
1 files changed, 61 insertions, 0 deletions
diff --git a/doc/man/alter_table.l b/doc/man/alter_table.l new file mode 100644 index 0000000000..88374b2fdf --- /dev/null +++ b/doc/man/alter_table.l @@ -0,0 +1,61 @@ +.\" This is -*-nroff-*- +.\" XXX standard disclaimer belongs here.... +.\" $Header$ +.TH "ALTER TABLE" SQL 11/5/95 Postgres95 Postgres95 +.SH NAME +alter table \(em add attributes to a class +.SH SYNOPSIS +.nf +\fBalter table\fR classname [*] + \fBadd column\fR attname type + +.fi +.SH DESCRIPTION +The +.BR "alter table" +command +causes a new attribute to be added to an existing class, +.IR classname . +The new attributes and their types are specified +in the same style and with the the same restrictions as in +.IR create table (l). +.PP +In order to add an attribute to each class in an entire inheritance +hierarchy, use the +.IR classname +of the superclass and append a \*(lq*\*(rq. (By default, the +attribute will not be added to any of the subclasses.) This should +.BR always +be done when adding an attribute to a superclass. If it is not, +queries on the inheritance hierarchy such as +.nf +select * from super* s +.fi +will not work because the subclasses will be missing an attribute +found in the superclass. +.PP +For efficiency reasons, default values for added attributes are not +placed in existing instances of a class. That is, existing instances +will have NULL values in the new attributes. If non-NULL values are +desired, a subsequent +.IR update (l) +query should be run. +.PP +You must own the class in order to change its schema. +.SH EXAMPLE +.nf +-- +-- add the date of hire to the emp class +-- +alter table emp add column hiredate abstime +.fi +.nf +-- +-- add a health-care number to all persons +-- (including employees, students, ...) +-- +alter table person * add column health_care_id int4 +.fi +.SH "SEE ALSO" +create table (l), +update (l). |