Re: What is the right syntax for retrieving the last_insert_id() inPostgresql ?

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От Sándor Daku
Тема Re: What is the right syntax for retrieving the last_insert_id() inPostgresql ?
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Msg-id CAKyoTgZxcU2kCk7e0gH+15JkWJvsERAkLj0=DKaXU3Fq7-T8zg@mail.gmail.com
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Ответ на Re: What is the right syntax for retrieving the last_insert_id() inPostgresql ?  (Karen Goh <karenworld@yahoo.com>)
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On Tue, 3 Mar 2020 at 16:50, Karen Goh <karenworld@yahoo.com> wrote:
Hi Pavel,

Using this as reference and your link :

https://dba.stackexchange.com/questions/3281/how-do-i-use-currval-in-postgresql-to-get-the-last-inserted-id

I tried :

select lastval('t_id') from table_tutor;

but it is not working.

Is there any tutorial out there that teaches the exact syntax ?

Thanks & regards,
Karen
On Sunday, March 1, 2020, 06:27:00 PM GMT+8, Pavel Stehule <pavel.stehule@gmail.com> wrote:




ne 1. 3. 2020 v 11:18 odesílatel Karen Goh <karenworld@yahoo.com> napsal:
Hi,

I hope I am posting on the right forum.  I googled but I can't find any solution pertaining to my problem.

Could someone know what is the syntext for last_insert_id() in Postgresql for me to insert into my sql execute query?

Postgres has not last_insert_id function. Maybe you think "lastval" function


Regards

Pavel


public int getTutorById() {
                openConnection();
                int tutor_id = 0;
                try {
                        Statement stmt3 = connection.createStatement();
                        ResultSet rs = stmt3.executeQuery("SELECT last_insert_id() from xtutor");
                        {
                                while (rs.next()) {
                                        tutor_id = rs.getInt(1);                                                       
                                }
                        }
                } catch (SQLException e) {
                        e.printStackTrace();
                }
                return tutor_id;
        }

org.postgresql.util.PSQLException: ERROR: function last_insert_id() does not exist
  Hint: No function matches the given name and argument types. You might need to add explicit type casts.
  Position: 8
        at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2440)
        at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:2183)
        at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:308)
        at org.postgresql.jdbc.PgStatement.executeInternal(PgStatement.java:441)
        at org.postgresql.jdbc.PgStatement.execute(PgStatement.java:365)
        at org.postgresql.jdbc.PgStatement.executeWithFlags(PgStatement.java:307)
        at org.postgresql.jdbc.PgStatement.executeCachedSql(PgStatement.java:293)
        at org.postgresql.jdbc.PgStatement.executeWithFlags(PgStatement.java:270)
        at org.postgresql.jdbc.PgStatement.executeQuery(PgStatement.java:224)
        at daoMySql.tutorDAOImpl.getTutorById(tutorDAOImpl.java:202)
        at daoMySql.tutorDAOImpl.getAlltutors(tutorDAOImpl.java:161)
        at business.manager.getAlltutors(manager.java:99)

The generated id is successfully generated by JDBC.

The errors when I tested in out using PGAdmin4 is

ERROR:  function last_insert_id() does not exist
LINE 1: SELECT last_insert_id() from xtutor;
               ^
HINT:  No function matches the given name and argument types. You might need to add explicit type casts.
SQL state: 42883
Character: 8

Postgresql 11, Windows 11

Thanks. 

 Hi,

Expanding a bit on John's answer, if you are using a serial or bigserial field Postgres makes a sequence for that field.
For example:
create table xtutor(
  t_id serial,
  ...
  ...

results a sequence named xtutor_t_id_seq(The schema is tablename_fieldname_seq)

And when you check the table structure with \d xtutor you'll see something like this:
Column     |            Type             | Collation | Nullable |                       Default
t_id            | integer                     |               | not null   | nextval('xtutor_t_id_seq'::regclass)

You can query the sequence as a table:

SELECT * FROM xtutor_t_id_seq;

or get the next value for a sequence(This advances the sequence as well):

SELECT nextval('xtutor_t_id_seq');

However...

Your example code looks like you are looking for the id of the most recently inserted tutor in which case a better solution would be replacing your select with this:
SELECT max(t_id) from xtutor;

Regards,
Sándor

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