I'm new to databases. I want to find the Duplicate records from the database table which is already created i.e. i m not concern about to prevent duplicate insertion but i wanted to know the duplicate records.
i tried with
Distinct
key word but it will show the records by removing duplicate data,
and after that i tried
unique index
which will say the the table name which are having duplicate records but not show or give duplicate records.
thanks in advance.
List the columns that make a record a duplicate and then group by them and count the occourances
select col1. col2
from your_table
group by col1, col2
having count(*) > 1
The having clause lists only those having more than one enry in the table.
Related
I am trying to find out how many of my rows are duplicates with any other row in my table.
Any help would be really appreciated
Select *
From DB
This gives me a count of all rows but I can’t figure out how to get only duplicates
If you don't provide more details then I can only answer in generic terms. You could create a query like this:
select
custom_key,
count(0) as occurrences
from
table
group by
custom_key
having
occurrences > 1
;
with custom_key being the field or fields which make a record unique or not.
I need to remove duplicate rows in my Access database, does anyone have generic query to do this? As I have this problem with multiple tables
There are two things you need to do,
Determine what the criteria are for a unique record - what is the list of columns where two, or more, records would be considered duplicates, e.g. JobbID and HisGuid
Decide what you want to do with the duplicate records - do you want to hard delete them, or set the IsDeleted flag that you have on the table
Once you've determined the criteria that you want to use for uniqueness you then need to pick 1 record from each group of duplicates to retain. A query along the lines of:
SELECT MAX(ID)
FROM MyTable
GROUP
BY JobbID, HisGuid
Will give you (and I've assumed that the ID column is an auto-increment/identity column that is unique across all records in the table) the highest value for each group of records where JobbID and HisGuid are both the same. You could use MIN(ID) if you want, it's up to you - you just need to pick ONE record from each group to keep.
Assuming that you want to set the IsDeleted flag on the records you don't want to keep, you can then incorporate this into an update query:
UPDATE MyTable
SET IsDeleted = 1
WHERE ID NOT IN
(
SELECT MAX(ID)
FROM MyTable
GROUP
BY JobbID, HisGuid
)
This takes the result of the query that retrieves the highest IDs and uses it to say set IsDeleted to 1 for all the records where the ID isn't the highest ID for each group of records where JobbID and HisGuid are the same.
The only part I can't help you with is running these queries in Access as I don't have it installed on the PC I'm using right now and my memory is a bit rusty regarding how/where to run arbitrary queries.
I have below query and by using that i can find out duplicates on particular
keys. I have 335 columns in table so query will be bigger if mention all column names in the query
select stone_id,charge_title,count(*) from table group by stone_id,charge_title having count(*) > 1
But i want to find out duplicates on all keys from table by better way.
Please suggest solution
I'm using Access 2007.
I have a table with about 20 fields. One of those fields is an autonumber ID, so it's unique. I have a lot of records in this table that only differ in their autonumber ID. I can't just delete the ones with odd or even IDs, because some pairs of duplicates have both odds or both evens. Any ideas on how to select one record from each pair for deletion?
I know this could probably be done with VBA, but I'm not really familiar with Access VBA yet, so I'm looking for a purely SQL-based solution.
DELETE *
FROM yourTable
WHERE id NOT IN
( SELECT min(id)
FROM yourTable
GROUP BY field2
, filed3
, field4
, etc... <--- all other fields, except id
)
delete the ones that are not min(id), grouped by the other columns that mean equivalence.
How do delete duplicate records in a DB2 table? I want to be left with a single record for each group of dupes.
Create another table "no_dups" that has exactly the same columns as the table you want to eliminate the duplicates from. (You may want to add an identity column, just to make it easier to identify individual rows).
Insert into "no_dups", select distinct column1, column2...columnN from the original table. The "select distinct" should only bring back one row for every duplicate in the original table. If it doesn't you may have to alter the list of columns or have a closer look at your data, it may look like duplicate data but actually is not.
When step 2 is done, you will have your original table, and "no_dups" will have all the rows without duplicates. At this point you can do any number of things - drop and rename tables, or delete all from the original and insert into the original, select * from no_dups.
If you're running into problems identifying duplicates, and you've added an identity column to "no_dups," you should be able to delete rows one by one using the identity column value.