mysql 从字符串列表中获取不同的标记

Question

我在 mysql 中有一个查询，group concats 记录并给出一个具有冗余标记的值。以下是查询的输出:

Problem Area->ACC-HO->ACC-HO->Credit Note (C/N)->Problem description ->Problem description 

但是我想要这个字符串的不同标记如下

Problem Area->ACC-HO->Credit Note (C/N)->Problem description 

有没有办法在 sql SELECT 查询本身中执行此操作？

编辑这是 schema and query以下是我的查询:

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

在 GROUP CONCAT 中添加 DISTINCT，这样它只会连接唯一值。

SELECT GROUP_CONCAT(DISTINCT colName),....
FROM   ...
WHERE  ...
GROUP BY ...

SQLFiddle Demo