从当前id SQL PHP获取两个上一行和下一行数据

i have a table with database and i want get two data before current id and get two data after current id.

primary_key     id
1               345
2               356
3               400
4               102
5               210
6               190

Case:

• If current id defined 400, the results as before is 356 & 345 and after is 102 & 210
• If current id defined 210, the results as before is 102 & 400 and after is 190
• If current id defined 356, the results as before is 345 and after is 400 & 102
• If current id defined 345, the results as before is NULL and after is 356 & 400
• If current id defined 190, the results as before is 210 & 102 and after is NULL

I try this SQL but not working fine,

$define_id = 400;

SELECT *
FROM table_name

WHERE ( 
    id = IFNULL(
        (
            SELECT MIN(id)
            FROM table_name
            WHERE id > $define_id
        ), 0 )

    OR id = IFNULL(
        (
            SELECT MAX(id)
            FROM table_name
            WHERE id < $define_id
        ), 0 )
) 

LIMIT 2

The code success to get before and after data, but only one before and one after. I want get result two before and two after.

Please help.

Tried with the outputs you mentioned in the question. If this is not you want please explain more clearly.

    CREATE TABLE IF NOT EXISTS `docs` (
  `primary_key` int(6) unsigned NOT NULL,
  `id` int(3) unsigned NOT NULL,
  PRIMARY KEY (`primary_key`,`id`)
) DEFAULT CHARSET=utf8;
INSERT INTO `docs` (`primary_key`, `id`) VALUES
  ('1', '345'),
  ('2', '356'),
  ('3', '400'),
  ('4', '102'),
  ('5', '210'),
  ('6', '190');

Query

(SELECT * FROM docs WHERE primary_key < (SELECT primary_key FROM docs WHERE id = 400) ORDER BY primary_key DESC LIMIT 2)
UNION ALL
(SELECT * FROM docs WHERE primary_key > (SELECT primary_key FROM docs WHERE id = 400) ORDER BY primary_key ASC LIMIT 2);

Sqlfiddle link http://sqlfiddle.com/#!9/e11c8d/2

One method uses union all for the two groups:

(select 'before' as which, t.*
 from t cross join
      (select primary_key from t where id = $define_id) x
 where t.primary_key < x.primary_key
 order by t.primary_key desc
 limit 2
) union all
(select 'after' as which, t.*
 from t cross join
      (select primary_key from t where id = $define_id) x
 where t.primary_key > x.primary_key
 order by t.primary_key asc
 limit 2
);

You can do it with min and max functions, So for next

SELECT * FROM `table` WHERE  id = (select min(id) from `table` where id > YOUR_ID)

And for previous:

SELECT * from `table` where id = (select max(id) from table where id < YOUR_ID)