Index: lams_tool_assessment/src/java/org/lamsfoundation/lams/tool/assessment/dbupdates/patch20140101.sql
===================================================================
diff -u -r6c5d0c6b8ff17d661580df2c265f2dcabfe7d76c -r54dd2285aa0ecea6030a369e81355cb4a8d4b09d
--- lams_tool_assessment/src/java/org/lamsfoundation/lams/tool/assessment/dbupdates/patch20140101.sql	(.../patch20140101.sql)	(revision 6c5d0c6b8ff17d661580df2c265f2dcabfe7d76c)
+++ lams_tool_assessment/src/java/org/lamsfoundation/lams/tool/assessment/dbupdates/patch20140101.sql	(.../patch20140101.sql)	(revision 54dd2285aa0ecea6030a369e81355cb4a8d4b09d)
@@ -8,7 +8,8 @@
 ALTER TABLE tl_laasse10_session ADD COLUMN group_leader_uid BIGINT;
 ALTER TABLE tl_laasse10_session ADD INDEX FK_laasse10_session_1 (group_leader_uid), ADD CONSTRAINT tl_laasse10_session FOREIGN KEY (group_leader_uid) REFERENCES tl_laasse10_user (uid) ON DELETE CASCADE ON UPDATE CASCADE;
 
--- adding a constraint to the assessment user table so no same user_id and session_id can be repetead 
+-- Adding a constraint to the assessment user table so no same user_id and session_id can be repetead 
+-- (Please, note there are some duplicate users exist (their session_uid is null), they got formed when techers created questions in authoring. It's required to keep track of questions' authors.) 
 ALTER TABLE tl_laasse10_user ADD UNIQUE INDEX(user_id, session_uid);
 
 ----------------------Put all sql statements above here-------------------------
Index: lams_tool_lamc/src/java/org/lamsfoundation/lams/tool/mc/dbupdates/patch20140101.sql
===================================================================
diff -u -r6c5d0c6b8ff17d661580df2c265f2dcabfe7d76c -r54dd2285aa0ecea6030a369e81355cb4a8d4b09d
--- lams_tool_lamc/src/java/org/lamsfoundation/lams/tool/mc/dbupdates/patch20140101.sql	(.../patch20140101.sql)	(revision 6c5d0c6b8ff17d661580df2c265f2dcabfe7d76c)
+++ lams_tool_lamc/src/java/org/lamsfoundation/lams/tool/mc/dbupdates/patch20140101.sql	(.../patch20140101.sql)	(revision 54dd2285aa0ecea6030a369e81355cb4a8d4b09d)
@@ -11,7 +11,15 @@
 -- Put automatic letters in front of MCQ answers
 ALTER TABLE tl_lamc11_content ADD COLUMN prefix_answers_with_letters TINYINT(1) NOT NULL DEFAULT 1;
 
--- Adding a constraint to the MCQ user table so no same user_id and session_id can be repetead 
+-- Adding a constraint to the MCQ user table so no same user_id and session_id can be repetead. 
+-- In order to achieve this remove duplicate users and according attempts. 
+CREATE TABLE temp_select AS SELECT MAX(uid) uid
+FROM tl_lamc11_que_usr GROUP BY que_usr_id, mc_session_id;
+ALTER TABLE temp_select ADD INDEX index1 (uid ASC);
+DELETE FROM tl_lamc11_usr_attempt WHERE que_usr_id NOT IN (SELECT uid FROM temp_select);
+DELETE FROM tl_lamc11_que_usr WHERE uid NOT IN (SELECT uid FROM temp_select);
+DROP TABLE temp_select;
+
 ALTER TABLE tl_lamc11_que_usr ADD UNIQUE INDEX(que_usr_id, mc_session_id);
 
 ----------------------Put all sql statements above here-------------------------
Index: lams_tool_laqa/src/java/org/lamsfoundation/lams/tool/qa/dbupdates/patch20140101.sql
===================================================================
diff -u -r6c5d0c6b8ff17d661580df2c265f2dcabfe7d76c -r54dd2285aa0ecea6030a369e81355cb4a8d4b09d
--- lams_tool_laqa/src/java/org/lamsfoundation/lams/tool/qa/dbupdates/patch20140101.sql	(.../patch20140101.sql)	(revision 6c5d0c6b8ff17d661580df2c265f2dcabfe7d76c)
+++ lams_tool_laqa/src/java/org/lamsfoundation/lams/tool/qa/dbupdates/patch20140101.sql	(.../patch20140101.sql)	(revision 54dd2285aa0ecea6030a369e81355cb4a8d4b09d)
@@ -8,7 +8,15 @@
 ALTER TABLE tl_laqa11_session ADD COLUMN qa_group_leader_uid BIGINT;
 ALTER TABLE tl_laqa11_session ADD INDEX FK_laqa11_session1 (qa_group_leader_uid), ADD CONSTRAINT FK_laqa11_session1 FOREIGN KEY (qa_group_leader_uid) REFERENCES tl_laqa11_que_usr (uid) ON DELETE CASCADE ON UPDATE CASCADE;
 
--- adding a constraint to the QA user table so no same user_id and session_id can be repetead 
+-- Adding a constraint to the QA user table so no same que_usr_id and qa_session_id can be repetead 
+-- In order to achieve this remove duplicate users and according responses. 
+CREATE TABLE temp_select AS SELECT MAX(uid) uid
+FROM tl_laqa11_que_usr GROUP BY que_usr_id, qa_session_id;
+ALTER TABLE temp_select ADD INDEX index1 (uid ASC);
+DELETE FROM tl_laqa11_usr_resp WHERE que_usr_id NOT IN (SELECT uid FROM temp_select);
+DELETE FROM tl_laqa11_que_usr WHERE uid NOT IN (SELECT uid FROM temp_select);
+DROP TABLE temp_select;
+
 ALTER TABLE tl_laqa11_que_usr ADD UNIQUE INDEX(que_usr_id, qa_session_id);
 
 ----------------------Put all sql statements above here-------------------------
Index: lams_tool_vote/src/java/org/lamsfoundation/lams/tool/vote/dbupdates/patch20131227.sql
===================================================================
diff -u -r96866054a8598fbe1b6719c40ea9a5ed898f5daf -r54dd2285aa0ecea6030a369e81355cb4a8d4b09d
--- lams_tool_vote/src/java/org/lamsfoundation/lams/tool/vote/dbupdates/patch20131227.sql	(.../patch20131227.sql)	(revision 96866054a8598fbe1b6719c40ea9a5ed898f5daf)
+++ lams_tool_vote/src/java/org/lamsfoundation/lams/tool/vote/dbupdates/patch20131227.sql	(.../patch20131227.sql)	(revision 54dd2285aa0ecea6030a369e81355cb4a8d4b09d)
@@ -8,7 +8,15 @@
 ALTER TABLE tl_lavote11_session ADD COLUMN group_leader_uid BIGINT;
 ALTER TABLE tl_lavote11_session ADD INDEX FK_lavote11_session_1 (group_leader_uid), ADD CONSTRAINT tl_lavote11_session FOREIGN KEY (group_leader_uid) REFERENCES tl_lavote11_usr (uid) ON DELETE CASCADE ON UPDATE CASCADE;
 
--- adding a constraint to the vote user table so no same user_id and vote_session_id can be repetead 
+-- Adding a constraint to the vote user table so no same user_id and vote_session_id can be repetead 
+-- In order to achieve this remove duplicate users and according attempts. 
+CREATE TABLE temp_select AS SELECT MAX(uid) uid
+FROM tl_lavote11_usr GROUP BY user_id, vote_session_id;
+ALTER TABLE temp_select ADD INDEX index1 (uid ASC);
+DELETE FROM tl_lavote11_usr_attempt WHERE que_usr_id NOT IN (SELECT uid FROM temp_select);
+DELETE FROM tl_lavote11_usr WHERE uid NOT IN (SELECT uid FROM temp_select);
+DROP TABLE temp_select;
+
 ALTER TABLE tl_lavote11_usr ADD UNIQUE INDEX(user_id, vote_session_id);
 
 ----------------------Put all sql statements above here-------------------------