Question

I am trying to create pagination of records from a sql statement, I was able to get next and previous for all but the last record shows the previous record as next due to the sql query only returning 1 row instead of 2. I am setting next based on the first result and previous as the second result.

The data:

• Apple
• Banana
• Grape
• Orange

The sql:

select * 
from (select top 1 fruit 
      FROM table 
      where fruit > 'Banana' 
      order by fruit asc) as x 

UNION ALL 

select * 
from (select top 1 fruit 
      FROM table 
      where fruit < 'Banana' order by fruit desc) as y

The result:

fruit
--------
Grape
Apple

This works great!

For the first record – I get the correct result for the first record being the true next.
For the last record – I get one result which is the second query that gets the previous record. However I have no way of knowing its the last record so it outputs as Next instead of Previous.

How would I determine that is the last record and the single row being returned is actually the previous?

OR

How can I have the query return a NULL row for the Next query? So I can test against a NULL result?

BONUS POINTS!

How can I have one query that will give me first record, last record and next and previous so I could enable circular pagination? If on first record show last record as previous. If on last record show next record as first record?

Answer 1

SELECT
  *
FROM
(
  SELECT
    MIN(fruit)   as first,
    MAX(fruit)   as previous
  FROM
    yourTable
  WHERE
    fruit < 'banana'
)
CROSS JOIN
(
  SELECT
    MIN(fruit)   as next,
    MAX(fruit)   as last
  FROM
    yourTable
  WHERE
    fruit > 'banana'
)

Or, shorter, but I’m not sure that it would be more performant…

SELECT
  MIN(CASE WHEN fruit < 'banana' THEN fruit END)   as first,
  MAX(CASE WHEN fruit < 'banana' THEN fruit END)   as previous,
  MIN(CASE WHEN fruit > 'banana' THEN fruit END)   as next,
  MAX(CASE WHEN fruit > 'banana' THEN fruit END)   as last
FROM
  yourTable

Or, as a final wierd option…

SELECT
  (SELECT TOP 1 fruit FROM yourTable WHERE fruit < 'banana' ORDER by fruit ASC)  AS first,
  (SELECT TOP 1 fruit FROM yourTable WHERE fruit < 'banana' ORDER by fruit DESC) AS previous,
  (SELECT TOP 1 fruit FROM yourTable WHERE fruit > 'banana' ORDER by fruit ASC)  AS next,
  (SELECT TOP 1 fruit FROM yourTable WHERE fruit > 'banana' ORDER by fruit DESC) AS last

(This may be usefull if you have thousands+ of records, as each is search quickly and separately.)