Condition: use DB2 dba backend.

Send 2 values to a zabbix trapper items in the same second.
These values correctly saved to database with increasing nanoseconds.

But on latest data page, an SQL:

SELECT * FROM (SELECT * FROM history h WHERE h.itemid='91702' AND h.clock>1543221807 ORDER BY h.clock DESC) WHERE rownum BETWEEN 0 AND 2

Gives incorrectly sorted values.

A base of the query with better formatting for readability:

SELECT
 ITEMID,
 CLOCK,
 timestamp('1970-01-01-02.00.00') + (clock) seconds as clock_converted,
 cast (VALUE as Integer) as VALUE,
 NS
FROM history h WHERE h.itemid='91702' AND h.clock>1543221807 ORDER BY h.clock DESC

gives this result:

SQL:

SELECT * FROM (--previous SQL--)
WHERE rownum BETWEEN 0 AND 2

returns only first 2 lines of previous result:

Maybe something like sorting by NS should be added.:

SELECT * FROM history h WHERE h.itemid='91702' AND h.clock>1543221807 order by CLOCK desc, NS desc fetch first 2 rows only

In PHP these 2 values are considered as already sorted:

	$lastHistory = isset($history[$item['itemid']][0]) ? $history[$item['itemid']][0] : null;
	$prevHistory = isset($history[$item['itemid']][1]) ? $history[$item['itemid']][1] : null;

so, from 2 values 1st one will be considered as "Latest value" 

We observed this behavior in frontend many times, but I think screenshots are redundant.

Just in case - on MySQL backend everything is fine itself:

SELECT * FROM history_uint h WHERE h.itemid='28515' AND h.clock>1543226958 ORDER BY h.clock DESC LIMIT 2

where 1543226958 is timestanm for last 24hours - for safety as we know.
result:

+--------+------------+-------+-----------+
| itemid | clock      | value | ns        |
+--------+------------+-------+-----------+
|  28515 | 1543313069 |    33 | 809401834 |
|  28515 | 1543313069 |    22 | 805209006 |
+--------+------------+-------+-----------+