?
Solved

Finding missing records in SQL table

Posted on 2014-09-04
5
Medium Priority
?
116 Views
Last Modified: 2014-11-28
The table stored in mySQL database contains the ID column, which is a number between 2000000 and 4000000. The numbers are ordered and sequential (increment by 1). I need a SQL query which can loop through this range and find all missing records (the database should contain 2000000 records, but currently contains only 1800000).

Thank you, experts!
0
Comment
Question by:cyber-33
5 Comments
 
LVL 32

Expert Comment

by:Daniel Wilson
ID: 40303733
Create a table of numbers, 2 million to 4 million.
create table numbers (N bigint);
then do a loop that inserts the numbers you need.

Next select the numbers that have no counterpart in your table.

Select N from numbers where not exists (Select ID from MyTable where ID = N);
0
 

Author Comment

by:cyber-33
ID: 40303742
I would need a script that populates the new table you are suggesting.

Also, there should be a simpler way finding the missing records by using a cursor and a single query.
0
 
LVL 26

Accepted Solution

by:
Tomas Helgi Johannsson earned 2000 total points
ID: 40303886
Hi!

Try this sql to find the missing values (gaps) in your sequence.

SELECT a.id+1 AS start, MIN(b.id) - 1 AS end
    FROM mytable AS a, mytable AS b
    WHERE a.id < b.id
    GROUP BY a.id
    HAVING start < MIN(b.id)

Open in new window


Regards,
       Tomas Helgi
0
 

Author Comment

by:cyber-33
ID: 40304311
Tomas, I tried running the query but it never came back... Can you please explain the logic behind it?
0
 
LVL 111

Expert Comment

by:Ray Paseur
ID: 40305885
... there should be a simpler way finding the missing records
Really?  How often do you need to do this?  If it's more than once, there is something suspicious about the overall design.  My sense is that any solution would be the best solution.  And with only two million records it's not a large process.

Please post the CREATE TABLE statement and show us some of your test data.  Armed with that we can almost certainly give you a tested-and-working code sample.
0

Featured Post

Hire Technology Freelancers with Gigs

Work with freelancers specializing in everything from database administration to programming, who have proven themselves as experts in their field. Hire the best, collaborate easily, pay securely, and get projects done right.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

An alternative to the "For XML" way of pivoting and concatenating result sets into strings, and an easy introduction to "common table expressions" (CTEs). Being someone who is always looking for alternatives to "work your data", I came across this …
This month, Experts Exchange sat down with resident SQL expert, Jim Horn, for an in-depth look into the makings of a successful career in SQL.
In this video, Percona Solution Engineer Dimitri Vanoverbeke discusses why you want to use at least three nodes in a database cluster. To discuss how Percona Consulting can help with your design and architecture needs for your database and infras…
With just a little bit of  SQL and VBA, many doors open to cool things like synchronize a list box to display data relevant to other information on a form.  If you have never written code or looked at an SQL statement before, no problem! ...  give i…

569 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question