James B. Byrne wrote:
I have a requirement to select the effective exchange rate for a
number of currencies as of a specific date and time. The rates may
come from several sources for the same currency. For some
currencies the rate may be set infrequently. I have come close to
getting this to work but cannot seem to get the last bit figured
out. Thus my appeal for help.
Here is what I have so far:
SELECT
fxr.currency_code_base AS fx_base,
fxr.currency_code_quote AS fx_quote,
fxr.effective_from AS fx_date,
fxr.currency_exchange_type AS fx_type,
fxr.currency_exchange_rate AS fx_rate
FROM
currency_exchange_rates AS fxr
LEFT OUTER JOIN
currency_exchange_rates AS fxr_j
ON
fxr.currency_code_base = fxr_j.currency_code_base
AND
fxr.currency_code_quote = fxr_j.currency_code_quote
AND
fxr.currency_exchange_type = fxr_j.currency_exchange_type
AND
fxr.effective_from >= fxr_j.effective_from
WHERE
fxr.currency_code_base = 'CAD'
AND
fxr.effective_from <= current_timestamp
GROUP BY
fx_base,
fxr.currency_code_quote,
fx_date,
fxr.currency_exchange_type,
fx_rate
HAVING
COUNT(fxr.currency_code_quote) = 1
ORDER BY
fx_base,
fxr.currency_code_quote,
fx_date DESC
I see currency_code_base = 'CAD', so you are looking for the most recent
Canadian exchange rate.
> The rates may
> come from several sources for the same currency.
What field is the source? currency_code_quote?
-Andy
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