如何向已包含数据的MariaDB表添加密钥？

Question

I'm trying to alter my table with MySQL but it will show an error on ALTER:

#1062 - Duplicate entry '5009-daring-1' for key 'doctermitem'

SQL query:

ALTER TABLE `wpi4_asp_index`
  ADD UNIQUE KEY `doctermitem` (`doc`,`term`,`blogid`),
  ADD KEY `term_ptype_bid_lang` (`term`(20),`post_type`(20),`blogid`,`lang`(10)),
  ADD KEY `rterm_ptype_bid_lang` (`term_reverse`(20),`post_type`(20),`blogid`,`lang`(10))

How can I solve this error?

Answer 1

You are trying create doctermitem as UNIQUE KEY , but already there are duplicate entry exist in that combination (as you mentioned '5009-daring-1'), so it is not allowing to add the doctermitem as UNIQUE KEY .

You need to manually remove those duplicate combination values, then it will allow to create the UNIQUE KEY

Answer 2

The columns you're targeting for a unique key are not unique - there is at least one row which is duplicated, there may be more.

Find them through a SQL statement:

select doc,
      term,
      blogid,
      count(*)
from wpi4_asp_index
group by doc,
      term,
      blogid
having count(*) > 1

You will then have to decide what the problem is and how to fix it. Broadly speaking, there are two likely causes:

• You have incorrect data. Fix the data, eg by deleting the duplicates.
• Your assumptions about uniqueness are wrong - you may need to add an additional column to your unique key.