Question

I’m querying a database in Android. The table is your ordinary table with values, nothing special.

What I need: return the two events that happened before and after the given timestamp.

Example: let’s suppose I have the table below, and my selection is 1332200003002:

_id |    Time       | Value
   ...    ...
n   | 1332200002000 | 145
n+1 | 1332200003001 | 98 (this is <= selection)
   (1332200003002 is here, between those two)
n+2 | 1332200004000 | 90 (this is > selection)
n+3 | 1332200005000 | 100
n+4 | 1332200005001 | 280

So, if my selection is 1332200003001, or 1332200003002… I’d want the returned rows to be n+1 and n+2, so that I can see that the Value went from 98 to 90.

What I’m using is a CursorLoader, so it must preferably fit into its usual call.

My code size thanks you!

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As a side note, I can guess safe values for BETWEEN (it IS working already), and then iterate the few remaining Cursor rows in Java to pinpoint the two rows that I need. However, this seems to me like a very common need, hence the question. Seems a waste to do it in Java with all those usual bumper tests we need to do with a Cursor.

Answer 1

SELECT *
FROM myTable LIMIT 2
OFFSET
  (SELECT _id
   FROM myTable
   WHERE time<=1332200003002
   ORDER BY time DESC LIMIT 1) - 1;

What this does:

Select 2 entries from the table. The offset of the first entry is selected as follows:

Choose the latest row where time <= 1332200003002, and calculate its offset from the first row.

The -1 at the end is needed if your _id values start at 1 rather than 0. (Change this value as needed to convert your _id values into zero-based offsets.)