PostgreSQL function for last inserted ID

Question

In PostgreSQL, how do I get the last id inserted into a table?

In MS SQL there is SCOPE_IDENTITY().

Please do not advise me to use something like this:

select max(id) from table

Manualmanubrium

why do you hate the max function? I think it's very simple. Is there any problem such as security? – Judaic

@Judaic there is problem if in between there are other operations, and more insertions(concurrent operations), means max id has changed, unless and until you take a lock explicitly and don't release it – Archangel

If the intended use case is to use the last inserted ID as part of the value of a subsequent insert, see this question. – Setting

The problem with the max function is that you want the latest inserted id, not the maximal value. – Derril

Answer 1

( tl;dr : goto option 3: INSERT with RETURNING )

Recall that in postgresql there is no "id" concept for tables, just sequences (which are typically but not necessarily used as default values for surrogate primary keys, with the SERIAL pseudo-type).

If you are interested in getting the id of a newly inserted row, there are several ways:

---

Option 1: CURRVAL(<sequence name>);.

For example:

  INSERT INTO persons (lastname,firstname) VALUES ('Smith', 'John');
  SELECT currval('persons_id_seq');

The name of the sequence must be known, it's really arbitrary; in this example we assume that the table persons has an id column created with the SERIAL pseudo-type. To avoid relying on this and to feel more clean, you can use instead pg_get_serial_sequence:

  INSERT INTO persons (lastname,firstname) VALUES ('Smith', 'John');
  SELECT currval(pg_get_serial_sequence('persons','id'));

Caveat: currval() only works after an INSERT (which has executed nextval() ), in the same session.

---

Option 2: LASTVAL();

This is similar to the previous, only that you don't need to specify the sequence name: it looks for the most recent modified sequence (always inside your session, same caveat as above).

---

Both CURRVAL and LASTVAL are totally concurrent safe. The behaviour of sequence in PG is designed so that different session will not interfere, so there is no risk of race conditions (if another session inserts another row between my INSERT and my SELECT, I still get my correct value).

However they do have a subtle potential problem. If the database has some TRIGGER (or RULE) that, on insertion into persons table, makes some extra insertions in other tables... then LASTVAL will probably give us the wrong value. The problem can even happen with CURRVAL, if the extra insertions are done intto the same persons table (this is much less usual, but the risk still exists).

---

Option 3: INSERT with RETURNING

INSERT INTO persons (lastname,firstname) VALUES ('Smith', 'John') RETURNING id;

This is the most clean, efficient and safe way to get the id. It doesn't have any of the risks of the previous.

Drawbacks? Almost none: you might need to modify the way you call your INSERT statement (in the worst case, perhaps your API or DB layer does not expect an INSERT to return a value); it's not standard SQL (who cares); it's available since Postgresql 8.2 (Dec 2006...)

---

Conclusion: If you can, go for option 3. Elsewhere, prefer 1.

Note: all these methods are useless if you intend to get the last inserted id globally (not necessarily by your session). For this, you must resort to SELECT max(id) FROM table (of course, this will not read uncommitted inserts from other transactions).

Conversely, you should never use SELECT max(id) FROM table instead one of the 3 options above, to get the id just generated by your INSERT statement, because (apart from performance) this is not concurrent safe: between your INSERT and your SELECT another session might have inserted another record.

Glycogenesis

LASTVAL() might be very evil, in case you add a trigger / rule inserting rows on itself into another table. – Lazes

SELECT max(id) unfortunately does not do the job either as soon as you start deleting rows. – Lashelllasher

@Glycogenesis Unless I missed something, if you have rows with IDs 1,2,3,4,5 and delete the rows 4 and 5, the last inserted ID is still 5, but max() returns 3. – Lashelllasher

@SimonA.Eugster Ah, no, by "last inserted id globally" I meant among the currently existing rows - that's what one is typicaly interested in - though I agree that my wording is not very good. – Glycogenesis

@Glycogenesis Ah okay, I was interested in the other one ;) – Lashelllasher

I m using CURRVAL in postgresql 8.2 however its giving me an error Currval not supported. Any work around for this is much appreciated. Thanks. – Federica

I just found out that there is problem with LASTVAL() is not just in case of triggers. When I insert something like insert into some_table (some_column) values (some_function()), then some_function() is apparently executed later than the insert itself, so if it also inserts something, then LASTVAL() will return the id of that. – Waadt

I would avoid using SELECT MAX() in favor of SELECT last_value FROM person_id_seq. Much faster. – Constantia

@GustavoPinsard : SELECT MAX() and SELECT last_value are different things, and can give different results. – Glycogenesis

A sample of how to use RETURNING id; to insert this in another table would be welcome! – Gavin

Just in case anyone's wondering--here is a list of how this is possible in other databases' languages. As the answer (kind of) alludes to, there is no directly SQL-compliant way to get the last-inserted ID – Selwin

How can I use RETURNING id within an SQL script fed to the psql command line tool? – Astto

Option 1 Worked for me like a charm. +1 – Bleacher

LASTVAL() is not evil, it's Triggers that are evil – Fatty

I know you have a tl;dr but I'm not sure why you ordered your options the way you did, you should move option 3 to option 1 as it's the most practical solution and the one that most users will go with anyways. – Toffey

option 3 is the simplest and convenient option. thanks – Groggy

How to store the last insert id in a variable in order to reuse it next time? – Digiovanni

How to do two inserts and use the returning id of the first insert in the second insert? – Geodesy

Where the inserted query returns the returned id...I'm unable to see anything after even insertion of row... – Lole

Answer 2

See the RETURNING clause of the INSERT statement. Basically, the INSERT doubles as a query and gives you back the value that was inserted.

Charlottecharlottenburg

Works as of version 8.2 and is the best and fastest solution. – Soekarno

maybe a quick explanation of how to use said returned id? – Cinder

@Andrew, If you run from psql command line this: insert into names (firstname, lastname) values ('john', 'smith') returning id;, then it simply outputs id just as if you ran select id from names where id=$lastid directly. If you want to save the return into a a variable, then insert into names (firstname, lastname) values ('john', 'smith') returning id into other_variable; If the statement containing the returning is the last statement in a function, then the id being returning'ed is returned by the function as a whole. – Chassis

Answer 3

Leonbloy's answer is quite complete. I would only add the special case in which one needs to get the last inserted value from within a PL/pgSQL function where OPTION 3 doesn't fit exactly.

For example, if we have the following tables:

CREATE TABLE person(
   id serial,
   lastname character varying (50),
   firstname character varying (50),
   CONSTRAINT person_pk PRIMARY KEY (id)
);

CREATE TABLE client (
    id integer,
   CONSTRAINT client_pk PRIMARY KEY (id),
   CONSTRAINT fk_client_person FOREIGN KEY (id)
       REFERENCES person (id) MATCH SIMPLE
);

If we need to insert a client record we must refer to a person record. But let's say we want to devise a PL/pgSQL function that inserts a new record into client but also takes care of inserting the new person record. For that, we must use a slight variation of leonbloy's OPTION 3:

INSERT INTO person(lastname, firstname) 
VALUES (lastn, firstn) 
RETURNING id INTO [new_variable];

Note that there are two INTO clauses. Therefore, the PL/pgSQL function would be defined like:

CREATE OR REPLACE FUNCTION new_client(lastn character varying, firstn character varying)
  RETURNS integer AS
$BODY$
DECLARE
   v_id integer;
BEGIN
   -- Inserts the new person record and retrieves the last inserted id
   INSERT INTO person(lastname, firstname)
   VALUES (lastn, firstn)
   RETURNING id INTO v_id;

   -- Inserts the new client and references the inserted person
   INSERT INTO client(id) VALUES (v_id);

   -- Return the new id so we can use it in a select clause or return the new id into the user application
    RETURN v_id;
END;
$BODY$
  LANGUAGE plpgsql VOLATILE;

Now we can insert the new data using:

SELECT new_client('Smith', 'John');

or

SELECT * FROM new_client('Smith', 'John');

And we get the newly created id.

new_client
integer
----------
         1

Obmutescence

This answer is incredibly helpful. You won't find any concrete RETURNING id INTO [new_variable] examples in the official Postrgres docs. – Tub

Answer 4

The other answers don't show how one might use the value(s) returned by RETURNING. Here's an example where the returned value is inserted into another table.

WITH inserted_id AS (
  INSERT INTO tbl1 (col1)
  VALUES ('foo') RETURNING id
)

INSERT INTO tbl2 (other_id) 
VALUES ((select id from inserted_id));

Justify

Top! Most straight-to-the-point answer – Kaolin

This gives kind of unexpected behavior if the tables are the same, in a test I did I got two records like {id: 2, lastid: null} and {id: 1, lastid: 2} – Outpouring

I don't think Postgres provides any guarantees about the evaluation order in this situation (that's my reading of this section from the docs. – Justify

Best answer - it runs immediately, and works exactly as intended. Thanks – Birdhouse

Answer 5

you can use RETURNING clause in INSERT statement,just like the following

wgzhao=# create table foo(id int,name text);
CREATE TABLE
wgzhao=# insert into foo values(1,'wgzhao') returning id;
 id 
----
  1
(1 row)

INSERT 0 1
wgzhao=# insert into foo values(3,'wgzhao') returning id;
 id 
----
  3
(1 row)

INSERT 0 1

wgzhao=# create table bar(id serial,name text);
CREATE TABLE
wgzhao=# insert into bar(name) values('wgzhao') returning id;
 id 
----
  1
(1 row)

INSERT 0 1
wgzhao=# insert into bar(name) values('wgzhao') returning id;
 id 
----
  2
(1 row)

INSERT 0 

Rappel

Answer 6

SELECT CURRVAL(pg_get_serial_sequence('my_tbl_name','id_col_name'))

You need to supply the table name and column name of course.

This will be for the current session / connection http://www.postgresql.org/docs/8.3/static/functions-sequence.html

Disobedient

Answer 7

See the below example

CREATE TABLE users (
    -- make the "id" column a primary key; this also creates
    -- a UNIQUE constraint and a b+-tree index on the column
    id    SERIAL PRIMARY KEY,
    name  TEXT,
    age   INT4
);

INSERT INTO users (name, age) VALUES ('Mozart', 20);

Then for getting last inserted id use this for table "user" seq column name "id"

SELECT currval(pg_get_serial_sequence('users', 'id'));

Dryly

Answer 8

You can use RETURNING id after insert query.

INSERT INTO distributors (id, name) VALUES (DEFAULT, 'ALI') RETURNING id;

and result:

 id 
----
  1

In the above example id is auto-increment filed.

Wiggins

Answer 9

For the ones who need to get the all data record, you can add

returning *

to the end of your query to get the all object including the id.

Shakta

Answer 10

The better way is to use Insert with returning. Though there are already same answers, I just want to add, if you want to save this to a variable then you can do this

insert into my_table(name) returning id into _my_id;

Cachinnate

Answer 11

Postgres has an inbuilt mechanism for the same, which in the same query returns the id or whatever you want the query to return. here is an example. Consider you have a table created which has 2 columns column1 and column2 and you want column1 to be returned after every insert.

# create table users_table(id serial not null primary key, name character varying);
CREATE TABLE
#insert into users_table(name) VALUES ('Jon Snow') RETURNING id;
 id 
----
  1
(1 row)

# insert into users_table(name) VALUES ('Arya Stark') RETURNING id;
 id 
----
  2
(1 row)

Dvandva

Answer 12

Try this:

select nextval('my_seq_name');  // Returns next value

If this return 1 (or whatever is the start_value for your sequence), then reset the sequence back to the original value, passing the false flag:

select setval('my_seq_name', 1, false);

Otherwise,

select setval('my_seq_name', nextValue - 1, true);

This will restore the sequence value to the original state and "setval" will return with the sequence value you are looking for.

Richey

Answer 13

I had this issue with Java and Postgres. I fixed it by updating a new Connector-J version.

postgresql-9.2-1002.jdbc4.jar

https://jdbc.postgresql.org/download.html: Version 42.2.12

https://jdbc.postgresql.org/download/postgresql-42.2.12.jar

Decompose

Answer 14

Based on @ooZman 's answer above, this seems to work for PostgreSQL v12 when you need to INSERT with the next value of a "sequence" (akin to auto_increment) without goofing anything up in your table(s) counter(s). (Note: I haven't tested it in more complex DB cluster configurations though...)

Psuedo Code

$insert_next_id = $return_result->query("select (setval('"your_id_seq"', (select nextval('"your_id_seq"')) - 1, true)) +1");

Curculio

There is no guarantee the step size is 1, and if there are any concurrent uses of the sequence this blows up horribly. – Braasch