mysql get distinct tokens from a string list - mysql

Question

I have a query in mysql that group concats records and gives a value having redundant tokens. Below is the output of the query:
Problem Area->ACC-HO->ACC-HO->Credit Note (C/N)->Problem description ->Problem description
But I want the distinct tokens of this string as below
Problem Area->ACC-HO->Credit Note (C/N)->Problem description
Is there a way to do this in the sql SELECT query itself?
EDIT
Here is schema and query
Below is my query:
SELECT
t2.transaction_id AS transaction_id,
GROUP_CONCAT(
CONCAT(
t1.display_text,
'->',
(CASE (NOT EXISTS (SELECT 1 FROM mst_node a WHERE a.parent_node_id = t1.node_id))
WHEN 1 THEN t1.display_text ELSE
(SELECT b.display_text AS DISPLAY FROM mst_node b
WHERE parent_node_id = t2.node_id AND b.display_seq = t2.entered_value)
END)
)
ORDER BY t2.logtime_stamp SEPARATOR '->'
) AS display_text
FROM
mst_node t1
JOIN trn_user_log t2
ON t1.app_id = t2.app_id AND t1.node_id = t2.node_id
WHERE (t1.app_id = 105)
AND t1.parent_node_id IS NOT NULL
AND t1.save_as_default IS NULL
GROUP BY transaction_id,
mobile_no
ORDER BY t2.transaction_id DESC,
t2.logtime_stamp,
t2.mobile_no

Answer 1

In you GROUP CONCAT add DISTINCT so it will only concatenate unique values.
SELECT GROUP_CONCAT(DISTINCT colName),....
FROM ...
WHERE ...
GROUP BY ...
SQLFiddle Demo

Answer 2

in your grouping clause, you can add another group by to group by this string column as well.
SELECT GROUP_CONCAT(myStringColumn),....
FROM ...
WHERE ...
GROUP BY myOtherColumn,myStringColumn

Answer 3

I was finally able to resolve my issue by using a UNION of two select queries and then doing a GROUP_CONCAT(DISTINCT column ORDER BY another_column).
Below is the query I used:
SELECT
transaction_id,
GROUP_CONCAT(DISTINCT display_text ORDER BY logtime_stamp SEPARATOR '->') AS display_text
FROM
(SELECT
t2.transaction_id AS transaction_id,
t2.logtime_stamp,
t1.display_text AS display_text
FROM mst_node t1
JOIN trn_user_log t2 ON t1.app_id = t2.app_id
AND t1.node_id = t2.node_id
WHERE (t1.app_id = 105)
AND t1.parent_node_id IS NOT NULL
AND t1.save_as_default IS NULL
UNION
SELECT t2.transaction_id AS transaction_id,t2.logtime_stamp,
CASE(NOT EXISTS (SELECT 1 FROM mst_node a WHERE a.parent_node_id = t1.node_id))
WHEN 1 THEN NULL
ELSE (SELECT b.display_text AS display_text FROM mst_node b WHERE parent_node_id = t2.node_id AND b.display_seq = t2.entered_value)
END AS display_text
FROM mst_node t1 JOIN trn_user_log t2
ON t1.app_id = t2.app_id AND t1.node_id = t2.node_id
WHERE (t1.app_id = 105)
AND t1.parent_node_id IS NOT NULL
AND t1.save_as_default IS NULL
ORDER BY transaction_id DESC,logtime_stamp
) AS T
GROUP BY transaction_id
ORDER BY transaction_id DESC,logtime_stamp