sql order by not working with decimal(18,6) - mysql

Question

The SQL query with order by clause is not working properly.
Query:
select cast(actual_qty as decimal(18,2)) from `Bin`
where warehouse = `Warehouse`.name
order by actual_qty desc
Output of above query:
303.00
550.00
0.00
3.00
The type of actual_qty is decimal(18,6). I tried using cast function in order by, didn't work.
Any help is much appreciated!!
Update1:
Here's my full query that is being fired:
select `tabWarehouse`.name, CONCAT_WS(" : ", "Actual Qty", ifnull( ( select round(`tabBin`.actual_qty, 2) as qty
from `tabBin` where `tabBin`.warehouse = `tabWarehouse`.name
and `tabBin`.item_code = '30440'
order by qty desc), 0) ) as actual_qty
from `tabWarehouse` where `tabWarehouse`.`name` like '%%%%' and ifnull(`tabWarehouse`.company, '') in ('', 'TILE TEST') and `tabWarehouse`.is_group = 0.0
limit 0, 20
The output is still the same which is not really ordered by the qty in a descending manner.
Update 2:
This is how my code looks:
query = """select tw.name,
CONCAT_WS(" : ", "Actual Qty", ifnull(round(`tabBin`.actual_qty, 2), 0 ) actual_qty
from `tabWarehouse` tw left join `tabBin` tb
on tb.warehouse = tw.name {bin_conditions}
where
tw.`{key}` like {txt}
{fcond} {mcond}
order by ifnull(round(tb.actual_qty, 2), 0) desc
limit
{start}, {page_len}
""".format(
bin_conditions=get_filters_cond(doctype, filter_dict.get("Bin"),bin_conditions, ignore_permissions=True),
# sub_query=sub_query,
key=searchfield,
fcond=get_filters_cond(doctype, filter_dict.get("Warehouse"), conditions),
mcond=get_match_cond(doctype),
start=start,
page_len=page_len,
txt=frappe.db.escape('%{0}%'.format(txt))
)

Answer 1

The cast in select doesn't change the type of the column -- and the order by is referring to the column in the table, not the expression in the select.
One option is to give it a new name and use that:
select cast(actual_qty as decimal(18,2)) as qty
from `Bin`
where warehouse = `Warehouse`.name
order by qty desc;
Or repeat the expression:
select cast(actual_qty as decimal(18,2)) as qty
from `Bin`
where warehouse = `Warehouse`.name
order by cast(actual_qty as decimal(18,2)) desc

Answer 2

There is no ORDER BY clause in your query.
The ORDER BY inside the correlated subquery is useless because that subquery will work only if it returns only 1 row and does not effect the final results.
Try this:
select tw.name,
CONCAT_WS(" : ", "Actual Qty", ifnull(round(tb.actual_qty, 2), 0)) actual_qty
from tabWarehouse tw left join tabBin tb
on tb.warehouse = tw.name and tb.item_code = '30440'
where tw.name like '%%%%'
and ifnull(tw.company, '') in ('', 'TILE SELECT')
and tw.is_group = 0.0
order by ifnull(round(tb.actual_qty, 2), 0) desc limit 0, 20
Also what is this condition:
`tabWarehouse`.`name` like '%%%%'