MySQL跨多个列搜索重复项

Question

APOLOGIES : I meant to say that the duplicates have to be within the same column.

I have the following code:

SELECT m.* FROM ( 
    SELECT text 
    FROM mytable 
    GROUP BY text 
    HAVING COUNT(*) > 1 ) q 
JOIN mytable m 
ON m.text = q.text

This enables me to search for duplicates on the column text and works fine. However, I have a table with:

q1a, q2a, q3a, q4a, q5a

What I'd like is for the the query to check in all the columns for duplicates - if this possible and could anyone give me a pointed?

Thanks,

H.

Answer 1

This may be what you need, it will give you the text that is duplicated, and on what rows and column the match is found;

SELECT GROUP_CONCAT(id) ids,q1a text,1 col 
FROM myTable GROUP BY text HAVING COUNT(*)>1
UNION
SELECT GROUP_CONCAT(id),q2a text,2 
FROM myTable GROUP BY text HAVING COUNT(*)>1
UNION
SELECT GROUP_CONCAT(id),q3a text,3  
FROM myTable GROUP BY text HAVING COUNT(*)>1
UNION
SELECT GROUP_CONCAT(id),q4a text,4  
FROM myTable GROUP BY text HAVING COUNT(*)>1
UNION
SELECT GROUP_CONCAT(id),q5a text,5 
FROM myTable GROUP BY text HAVING COUNT(*)>1

An SQLfiddle to test with .

Answer 2

If I undestand your question correctly, you could use a query like this:

SELECT m.*
FROM (
    SELECT txt FROM (
      SELECT q1a as txt FROM mytable
      UNION ALL
      SELECT q2a as txt FROM mytable
      UNION ALL
      SELECT q3a as txt FROM mytable
      UNION ALL
      SELECT q4a as txt FROM mytable
      UNION ALL
      SELECT q5a as txt FROM mytable) u
    GROUP BY
      txt
    HAVING COUNT(*)>1) q
  INNER JOIN mytable m
  ON q.txt IN (m.q1a, m.q2a, m.q3a, m.q4a, m.q5a)

Please see fiddle here .