Did you ever find a fix to this? I've been trying to upgrade as well. Tried from 1.9.7 to 2.0 and then 1.9.7 to 2.1 ...my error is slightly different, but close to yours:
DL sql execution error
More information about this error
I fixed it! You need to look at the table mdl_user_preferences for userid = 6350 and name=auth_forcepasswordchange (or email_send_count, etc.). You'll end up seeing more than one entry and you need to delete all but one of the records because this is supposed to be unique, ie.:
i.e.:
the debug info was: duplicate entry '6532-email_send_count' for key mdl_userpref_usename_uix'
So, the commands I ran were:
select * from mdl_user_preferences where name="email_send_count" and userid = 6532; +-------+--------+------------------+-------+
| id | userid | name | value |
+-------+--------+------------------+-------+
| 10347 | 6532 | email_send_count | 79 |
| 11196 | 6532 | email_send_count | 41 |
+-------+--------+------------------+-------+
2 rows in set (0.00 sec)
mysql> delete from mdl_user_preferences where name="email_send_count" and userid=6532 and id=10347;
Query OK, 1 row affected (0.00 sec)
Same problem here, this should fix the whole table in 1 command:
DELETE FROM `mdl_user_preferences` WHERE `id` IN (SELECT id FROM ( SELECT id,userid,name,count( * ) AS duplicities FROM `mdl_user_preferences` AS A GROUP BY userid,name HAVING COUNT( * ) >1 ) B );
You can use "SELECT *" instead of "DELETE" to preview the affected entries.
