从包含2亿条记录的表中选择一些记录

Question

I am new to sql so my terminologies might not be very correct.

I have a table Alignment which has got 250 million records. It has two columns chain_id1 and chain_id2. Some of these chains are foreign keys for chain_id from another table Centroid which has 22000 records.

Basically I need all those records which are have both chains as centroids.

I tried using the following query:

insert into NewAlignment(...) 
select .... 
from Alignment as A
   , Centroid  as C1
   , Centroid  as C2 
where (A.chain_id1 = C1.chain_id) 
  and (A.chain_id2 = C2.chain_id)

But the above query just stalls which is understandable looking at the size of the tables.

So I tried writing a script to scan through the tables and check for values and then insert in new table. In that way for 1000000 records it took about 13 minutes.

Is there any way to speed this up.

Thanks a lot.

Answer 1

You'll likely want to add indexes to your tables, particularly on Alignment.Chain_id1 , Alignment.Chain_id2 , and Centroid.Chain_id . This should help a lot.