How can I select adjacent rows to an arbitrary row (in sql or postgresql)?

Question

I want to select some rows based on certain criteria, and then take one entry from that set and the 5 rows before it and after it.

Now, I can do this numerically if ther

Answer 1

Here's another way to do it with analytic functions lead and lag. It would be nice if we could use analytic functions in the WHERE clause. So instead you need to use subqueries or CTE's. Here's an example that will work with the pagila sample database.

WITH base AS (
    SELECT lag(customer_id, 5) OVER (ORDER BY customer_id) lag, 
      lead(customer_id, 5) OVER (ORDER BY customer_id) lead, 
      c.*
    FROM customer c
    WHERE c.active = 1
    AND c.last_name LIKE 'B%'
) 
SELECT base.* FROM base 
JOIN (
  -- Select the center row, coalesce so it still works if there aren't 
  -- 5 rows in front or behind
  SELECT COALESCE(lag, 0) AS lag, COALESCE(lead, 99999) AS lead 
  FROM base WHERE customer_id = 280
) sub ON base.customer_id BETWEEN sub.lag AND sub.lead

The problem with sgriffinusa's solution is that you don't know which row_number your center row will end up being. He assumed it will be row 30.