Masis, Alexander (US SSA) wrote:
That will work reliably in a multi-user environment if and only if currval() returns the last value for the current connection. I assume this is the case but the description of currval() in the PostgreSQL documentation says "Return value most recently obtained withI was mapping C++ application code that works with mySQL to work with Postgres. There were a number of articles on line regarding the conversion from mySQL to Postgres like: http://en.wikibooks.org/wiki/Programming:Converting_MySQL_to_PostgreSQL http://groups.drupal.org/node/4680 http://jmz.iki.fi/blog/programming/converting_mysql_database_to_postgres ql http://www.raditha.com/blog/archives/000488.html However, I found the most difficult issue was related to a MySQL's "SELECT LAST_INSERT_ID()" sql call. If your code did not use LAST_INSERT_ID(), then you don't have to read this post. In MySQL "LAST_INSERT_ID()" is a MySQL's syntax that returns the last auto_increment type ID of the row(record) inserted in a table. In other words, if your MySQL table had a auto_increment datatype for a field, that field will automatically advance whenever a new record(row) is inserted into that table. It is sometimes handy to know what is the value of that ID, that has just been added to the table, so that that record(row) can be addressed/updated later. Well, in MySQL it's easy you just do: "SELECT LAST_INSERT_ID();" In Postgres, however it is not that simple. You have to know the name of so called "insert sequence". Postgres has a system function for that( SQL line below ). In Postgres you will have to provide the table and column name( "auto_increment" type in MySQL or "serial or bigserial" in Postgres). Here is that SQL query that returns the last inserted ID: "SELECT CURRVAL( pg_get_serial_sequence('my_tbl_name','id_col_name'));" Alexander Masis. nextval for specified sequence". There is no
mention that currval() returns the last value obtained by calling
nextval() for the current connection. Can someone confirm that
currval() returns the the value for the connection from which it is
called?Bill |
