LUA script: Nested loop inserts only last item - arrays

Question

I have two loops, a main loop and a sub-loop inside the main loop. Both loops populate the same table (and sub-table). But for some reason the sub-loop only stores the last added item in the nested table.
For instance, main group 1 has sub-groups stored as 1-9:
printTable(data[1][subItems][1]) -- returns error (index nil value)
printTable(data[1][subItems][9]) -- dumps table to console
If I break the sub-loop after one iteration then data[1][subItems][1] contains data
for i=startId, endId, 10 do
items = loadItems(i)
data[i] = {['items'] = items}
for x=i+1, i+10-1 do
subItems = loadItems(x)
print('adding items to sub-group: '..x..' for main group: '..i)
data[i]['subItems'] = {}
data[i]['subItems'][x] = {['items'] = subItems}
end
end
end
Since I'm printing some debug info inside the sub-loop, I know that, the code is being executed. And I know that loadItems(x) is getting the data on each iteration, because if i dump the loadItems(x) to console in the sub-loop, all is there on each iteration.
What is this wizardry?

Answer 1

Silly me, how could I miss it!
The answer is of course to move the data[i][subItems] = {} outside the sub-loop:
for i=startId, endId, 10 do
items = loadItems(i)
data[i] = {['items'] = items}
data[i]['subItems'] = {} <----------------------------------------------
for x=i+1, i+10-1 do
subItems = loadItems(x)
print('adding items to sub-group: '..x..' for main group: '..i)
data[i]['subItems'][x] = {['items'] = subItems}
end
end
end