Question

I have two tables that look something like this:

Checkpoint with field:

  Checkpoint_id
  Checkpoint_name

checkpoint_id is a primary key

Checkpoint_data with fields:

Checkpoint_id
sequence_number
data

(checkpoint_id, sequence_number) is the primary key

What I want to do, is get the checkpoint_id with its name, but also sum the length of all of the data that is linked via checkpoint_id. For example, I would want to get the length of sequence_number 1, 2, 3 and 4, and then add up the lengths off all of data and return it with the corresponding checkpoint id and name. The data field is a varchar

Answer 1

SELECT c.checkpoint_id, c.checkpoint_name, sum(length(cd.data))
FROM checkpoint c 
INNER JOIN checkpoint_data cd ON c.checkpoint_id = cd.checkpoint_id
GROUP BY c.checkpoint_id

EDIT:

SELECT c.checkpoint_id, c.checkpoint_name, sum(length(cd.data))
FROM checkpoint c 
INNER JOIN checkpoint_data cd ON c.checkpoint_id = cd.checkpoint_id
GROUP BY c.checkpoint_id, c.checkpoint_name