Michael Michael - 7 months ago 12
PHP Question

lastInsertId does not work in Postgresql

I am using Postgresql, when I want to use PDO to retrieve the latest insertion ID, I got a problem. Here is my code:

$db->lastInsertId('columnName');


The error message says

SQLSTATE[42P01]: Undefined table: 7 ERROR: relation "columnName" does not exist


I guess I have some misunderstanding about "sequence object" stated in the PHP Manual.

Note:

Returns the ID of the last inserted row, or the last value from a sequence object,
depending on the underlying driver. For example, PDO_PGSQL() requires you to specify the
name of a sequence object for the name parameter.


Currently, the "columnName" is the string of that auto-incremented attribute. Can anyone point out where I went wrong? Thanks.

Answer

PostgreSQL uses sequences to generate values for serial columns and serial columns are generally what is used for "auto-incrementing" columns in PostgreSQL. Sequences have names and are, in general, independent of any particular table so you could have one sequence generating unique IDs for several different tables; the sequence name is what lastInsertId wants as its argument:

For example, PDO_PGSQL() requires you to specify the name of a sequence object for the name parameter.

The sequence object created by PostgreSQL is automatically named [table]_[column]_seq, So:

$id = $db->lastInsertId('tableName_columnName_seq');