Returns ids of documents inserted or replaced by last statement in the current session.
The same value can be also received via @@session.last_insert_id variable:
mysql> select @@session.last_insert_id;
+--------------------------+
| @@session.last_insert_id |
+--------------------------+
| 11,32 |
+--------------------------+
1 rows in set
mysql> select LAST_INSERT_ID();
+------------------+
| LAST_INSERT_ID() |
+------------------+
| 25,26,29 |
+------------------+
1 rows in set SELECT @@system_variable [LIMIT [offset,] row_count]This is currently a placeholder query that does nothing and reports success. That is in order to keep compatibility with frameworks and connectors that automatically execute this statement.
However @@session.last_insert_id and LAST_INSERT_ID() report ID of documents these were inserted or replaced well at last statement.
mysql> select @@session.last_insert_id;
+--------------------------+
| @@session.last_insert_id |
+--------------------------+
| 11,32 |
+--------------------------+
1 rows in set
mysql> select LAST_INSERT_ID();
+------------------+
| LAST_INSERT_ID() |
+------------------+
| 25,26,29 |
+------------------+
1 rows in set Returns current connection id.
mysql> select CONNECTION_ID();
+-----------------+
| CONNECTION_ID() |
+-----------------+
| 6 |
+-----------------+
1 row in set (0.00 sec)