Index: lams_tool_lamc/src/java/org/lamsfoundation/lams/tool/mc/dbupdates/patch20131021.sql
===================================================================
diff -u
--- lams_tool_lamc/src/java/org/lamsfoundation/lams/tool/mc/dbupdates/patch20131021.sql	(revision 0)
+++ lams_tool_lamc/src/java/org/lamsfoundation/lams/tool/mc/dbupdates/patch20131021.sql	(revision 77064a0217543af7ac08d839f1d5c8205f91358a)
@@ -0,0 +1,19 @@
+-- Turn off autocommit, so nothing is committed if there is an error
+SET AUTOCOMMIT = 0;
+
+----------------------Put all sql statements below here-------------------------
+
+--LDEV-3138 Prevent erroneously creating 2 identical user results for 1 question in DB
+CREATE TABLE temp_select AS SELECT MAX(uid) uid
+FROM tl_lamc11_usr_attempt GROUP BY que_usr_id, mc_que_content_id;
+ALTER TABLE temp_select ADD INDEX index1 (uid ASC);
+DELETE FROM tl_lamc11_usr_attempt WHERE uid NOT IN (SELECT uid FROM temp_select);
+DROP TABLE temp_select;
+
+ALTER TABLE tl_lamc11_usr_attempt ADD UNIQUE INDEX attempt_unique_index (que_usr_id, mc_que_content_id);
+
+----------------------Put all sql statements above here-------------------------
+
+-- If there were no errors, commit and restore autocommit to on
+COMMIT;
+SET AUTOCOMMIT = 1;