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, PHP 8)
pg_last_oid — 返回上一条记录的 oid
说明
pg_last_oid() 用于检索分配给插入行的 OID。
从 PostgreSQL 7.2 开始 OID 字段成为可选项，在 PostgreSQL 8.1 中默认不存在。如果表中没有定义 OID 字段，程序员必须用 pg_result_status() 检查记录是否成功插入。
要在插入的行中获取 SERIAL 字段的值，必须使用 PostgreSQL CURRVAL
函数，命名需要最后一个值的序列。如果序列名称未知，则需要 pg_get_serial_sequence PostgreSQL 8.0 函数。
PostgreSQL 8.1 有一个函数 LASTVAL，它返回会话中最近使用的序列的值。这避免了对序列、表或列的命名需求。
注意:
本函数以前的名字为 pg_getlastoid()。
更新日志
| 版本 | 说明 |
|---|---|
| 8.1.0 |
现在 result 参数接受 PgSql\Result
实例，之前接受 resource。
|
示例
示例 #1 pg_last_oid() 示例
<?php
// 连接到数据库
pg_connect("dbname=mark host=localhost");
// 创建示例表
pg_query("CREATE TABLE test (a INTEGER) WITH OIDS");
// 插入一些数据
$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
