MySQL 查询返回重复+原始记录？

Question

So I have a table with duplicates and i want to update the original + duplicate values in that table. I can use the Update statement to update but I can't seem to figure out a query to return records that include both duplicate and original.

This is the query I'm using:

Select primary_id, user_number, duplicate, ignored from myTable 
group by user_number 
having count(user_number) > 1;

I have 27 unique user_number and all of them have at least 1 duplicate so I want the query to return at least 54 records (unique + duplicate) but it returns 27 records with unique only.

Goal is to change the values in duplicate and ignored columns to 1 .

Once i get all the records I can run the update query below:

update myTable 
set duplicate = 1, ignored = 1

primary_id is auto incremented id

Answer 1

You can use joins in update statements in MySQL.

UPDATE myTable AS t1
JOIN myTable AS t2 ON t1.user_number = t2.user_number 
  AND t1.primary_id < t2.primary_id
SET t2.duplicate = 1, t2.ignored = 1;

This updates a duplicate row with a greater primary_id and the same user_number as the first row where that user_number occured.

This naturally only affects rows that have duplicates, because if a row t1 does not have a duplicate, there will not be another row t2 for it to join to.