From: Christopher Browne <cbbrowne@acm.org>
To: pgsql-sql@postgresql.org
Subject: Re: Desc Commnad in pgsql?
Date: Sat, 19 Apr 2008 12:55:53 -0400
Message-ID: <87skxh3ht2.fsf@wolfe.cbbrowne.com> (raw)
References: <c4fdd6d00804170146l7aa56dbdy6a4ec006ad5eedc4@mail.gmail.com>
<c4fdd6d00804170147t6519649ldbaa5660302df3be@mail.gmail.com>
The world rejoiced as vikasraigupta@gmail.com (VG) wrote:
> Hello All,
> I like to know how can I achieve the same functionality that is give by desc commnad in mysql or oracle.
> Also specify me the book related to pgsql as a beginner.
> Presently my task is going to be communication of ruby with pgsql
> Thanks in advanced.
If you were referring to the usage of "desc" to indicate "descending
order", as in:
select * from some table order by id desc
well, that's pretty standard SQL usage, and will work much as it
would in MySQL(tm) or Oracle.
If you're looking for ways to "describe" a table, there are two
mechanisms:
1. SQL standard (probably SQL:1993) describes an
"information_schema" which contains tables or views that allow
querying database metadata in a fairly standard fashion.
PostgreSQL supports that.
2. Probably easier and friendlier, albeit nonportable, is to use
the psql "\d" command.
Here's an example:
cbbrowne@wolfe:~> psql ledgersmb Saturday 12:51:13
Welcome to psql 8.1.10, the PostgreSQL interactive terminal.
Type: \copyright for distribution terms
\h for help with SQL commands
\? for help with psql commands
\g or terminate with semicolon to execute query
\q to quit
ledgersmb=# \d acc_trans
Table "public.acc_trans"
Column | Type | Modifiers
----------------+---------+-------------------------------------------------------------
trans_id | integer |
chart_id | integer | not null
transdate | date | default date('now'::text)
source | text |
cleared | boolean | default false
fx_transaction | boolean | default false
project_id | integer |
memo | text |
invoice_id | integer |
amount | numeric |
entry_id | bigint | not null default nextval('acctrans_entry_id_seq'::regclass)
Indexes:
"acc_trans_pkey" PRIMARY KEY, btree (entry_id)
"acc_trans_chart_id_key" btree (chart_id)
"acc_trans_source_key" btree (lower(source))
"acc_trans_trans_id_key" btree (trans_id)
"acc_trans_transdate_key" btree (transdate)
Foreign-key constraints:
"$1" FOREIGN KEY (chart_id) REFERENCES chart(id)
"$2" FOREIGN KEY (chart_id) REFERENCES chart(id)
"$3" FOREIGN KEY (chart_id) REFERENCES chart(id)
"$4" FOREIGN KEY (chart_id) REFERENCES chart(id)
"acc_trans_chart_id_fkey" FOREIGN KEY (chart_id) REFERENCES chart(id)
You can query the schemas for all sorts of objects, complete with
tab-completion; type "\?" at the psql prompt to see all of the
internal psql commands. There is a whole section entitled
"Informational" that shows modifiers to \d to query various sorts of
objects.
For instance:
\dt will list all tables
\ds will list all sequences
\dv will list all views
and there's a further cast of ~20 variants for various different sorts
of objects.
--
let name="cbbrowne" and tld="gmail.com" in String.concat "@" [name;tld];;
http://linuxdatabases.info/info/postgresql.html
"Java and C++ make you think that the new ideas are like the old ones.
Java is the most distressing thing to hit computing since MS-DOS."
-- Alan Kay
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To: pgsql-sql@postgresql.org
Cc: cbbrowne@acm.org
Subject: Re: Desc Commnad in pgsql?
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