The way I nuderstand it, each value is emitted by a sequence only ONCE. If you retrieve a number (say 12) from a sequence using nextval(), the sequence will advance and subsequent calls to nextval() will return further numbers (after 12) in the sequence.
This means that if you use nextval() to retrieve a value to use as a primary key, you can be guaranteed that no other calls to nextval() on that sequence will return the same value. No race conditions, no transactions required.
That's what sequences are *for* afaik :^)
pg_last_oid
(PHP 4 >= 4.2.0, PHP 5, PHP 7)
pg_last_oid — Returns the last row's OID
Descrierea
pg_last_oid
( resource
$result
) : stringpg_last_oid() is used to retrieve the OID assigned to an inserted row.
OID field became an optional field from PostgreSQL 7.2 and will not be present by default in PostgreSQL 8.1. When the OID field is not present in a table, the programmer must use pg_result_status() to check for successful insertion.
To get the value of a SERIAL field in an inserted
row, it is necessary to use the PostgreSQL CURRVAL
function, naming the sequence whose last value is required. If the
name of the sequence is unknown, the pg_get_serial_sequence
PostgreSQL 8.0 function is necessary.
PostgreSQL 8.1 has a function LASTVAL that returns
the value of the most recently used sequence in the session. This avoids
the need for naming the sequence, table or column altogether.
Notă:
This function used to be called pg_getlastoid().
Parametri
-
result -
PostgreSQL query result resource, returned by pg_query(), pg_query_params() or pg_execute() (among others).
Valorile întoarse
A string containing the OID assigned to the most recently inserted
row in the specified connection, or false on error or
no available OID.
Exemple
Example #1 pg_last_oid() example
<?php
// Connect to the database
pg_connect("dbname=mark host=localhost");
// Create a sample table
pg_query("CREATE TABLE test (a INTEGER) WITH OIDS");
// Insert some data into it
$res = pg_query("INSERT INTO test VALUES (1)");
$oid = pg_last_oid($res);
?>
add a note
User Contributed Notes 6 notes
julian at e2-media dot co dot nz ¶
21 years ago
a dot bardsley at lancs dot ac dot uk ¶
21 years ago
As pointed out on a busy site some of the above methods might actually give you an incorrect answer as another record is inserted inbetween your insert and the select. To combat this put it into a transaction and dont commit till you have done all the work
webmaster at gamecrash dot net ¶
21 years ago
You could use this to get the last insert id...
CREATE TABLE test (
id serial,
something int not null
);
This creates the sequence test_id_seq. Now do the following after inserting something into table test:
INSERT INTO test (something) VALUES (123);
SELECT currval('test_id_seq') AS lastinsertid;
lastinsertid should contain your last insert id.
dtutar at yore dot com dot tr ¶
21 years ago
This is very useful function :)
function sql_last_inserted_id($connection, $result, $table_name, $column_name) {
$oid = pg_last_oid ( $result);
$query_for_id = "SELECT $column_name FROM $table_name WHERE oid=$oid";
$result_for_id = pg_query($connection,$query_for_id);
if(pg_num_rows($result_for_id))
$id=pg_fetch_array($result_for_id,0,PGSQL_ASSOC);
return $id[$column_name];
}
Call after insert, simply ;)
qeremy [atta] gmail [dotta] com ¶
12 years ago
Simply getting LAST_INSERT_ID;
<?php
// Note: waiting for "select" part from pg_query below.
// Note: separating the query parts using semicolons (;).
$qry = pg_query("
INSERT INTO users (id,uname,upass,rep) VALUES (DEFAULT,'bubu','a981v',0.19);
SELECT Currval('users_id_seq') LIMIT 1
");
// or
$qry = pg_query("
INSERT INTO users (id,uname,upass,rep) VALUES (DEFAULT,'bubu','a981v',0.19) RETURNING Currval('users_id_seq')");
$fch = pg_fetch_row($qry);
print_r($fch);
?>
Array
(
[0] => 3 -> Gotcha!
)
Jonathan Bond-Caron ¶
19 years ago
I'm sharing an elegant solution I found on the web (Vadim Passynkov):
CREATE RULE get_pkey_on_insert AS ON INSERT TO Customers DO SELECT currval('customers_customers_id_seq') AS id;
Every time you insert to the Customers table, postgreSQL will return a table with the id you just inserted. No need to worry about concurrency, the ressource is locked when the rule gets executed.
Note that in cases of multiple inserts:
INSERT INTO C1 ( ... ) ( SELECT * FROM C2);
we would return the id of the last inserted row.
For more info about PostgreSQL rules:
http://www.postgresql.org/docs/7.4/interactive/sql-createrule.html
