View source for Short Notes on PSQL

PSQL aka Postgres aka PostgreSQL... I prefer psql.

== Dump and Restore ==

<pre>dump:
$ pg_dump -h host -p 5432 -U user -F c -b -v -f /tmp/db_name.backup db_name
restore:
$ pg_restore -h host -p 5432 -U user -d db_name -v /tmp/db_name.backup</pre>

== Delete Duplicate Lines ==

Before you can add a <tt>unique</tt> constraint to a table, you have to make sure it does satisfy this criteria.

With <tt>table_T</tt> and columns <tt>criteria_1</tt>, ..., <tt>criteria_N</tt>.

<pre>
;;
;; list rows that do not satisfy the uniqueness constraint
;;
SELECT
    criteria_1,
    ...
    criteria_N,
    COUNT(*)
FROM
    table_T
GROUP BY
    criteria_1, ..., criteria_N
HAVING
    COUNT(*) > 1
ORDER BY
    criteria_1, ..., criteria_N;

;;
;; delete all rows that do not satisfy the constraint, keeping the ones with lowest id value
;;
DELETE  FROM
    table_T a
        USING table_T b
WHERE
    a.id > b.id
    AND a.criteria_1 = b.criteria_1
    ...
    AND a.criteria_N = b.criteria_N;
</pre>

== Set Sequence Value to Max of Table's ID ==

<pre>
SELECT setval('table_id_seq', (SELECT MAX(id) FROM table));
</pre>