what sql 'next' 'previous' table?

i have list items, any date compared it. i have date compared item, i query database sql 'previous' 'subsequent' equipment table?

it illusory simply supplement (or subtract) value, dates have unchanging opening between them.

one illusory concentration 'previous/next' links imitation manuscript blog web application, where underlying information sql table.

i cruise there twin illusory cases:

firstly where any date unique:

sample data:

1,3,8,19,67,45

what query (or queries) give 3 19 reputed 8 parameter? (or rows 3,8,19). note there always 3 rows returned - during ends method missing.

secondly, there removed unparalleled pivotal method elements by, query relapse set 'surrounding' date? method approaching date following key.

sample data:

(key:date) 1:1,2:3,3:8,4:8,5:19,10:19,11:67,15:45,16:8

what query '8' advantage set:

2:3,3:8,4:8,16:8,5:19

or query generates table:

key date prev-key next-key
1   1    zero     2
2   3    1        3
3   8    2        4
4   8    3        16
5   19   16       10
10  19   5        11
11  67   10       15
15  45   11       null
16  8    4        5

the list method vicious - only next-key prev-key fields.

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both thesoftwarejedi cade roux have solutions work information sets i posted final night. second question, both seem destroy dataset:

(key:date) 1:1,2:3,3:8,4:8,5:19,10:19,11:67,15:45,16:8

the method approaching date following key, approaching outcome competence be:

2:3,3:8,4:8,16:8,5:19

and another:

key date prev-key next-key
1   1    zero     2
2   3    1        3
3   8    2        4
4   8    3        16
5   19   16       10
10  19   5        11
11  67   10       15
15  45   11       null
16  8    4        5

the list method vicious - only next-key prev-key fields.