SQL Query? The question is how?

Question

Hi folks,
I am developing a finance program and I am having difficulty writing a SQL query to get the info that I need.
In short I have two tables:
TABLE 1: Currency Rates
FROM_CURRENCY (CURRENCY_ABRV)
TO_CURRENCY (CURRENCY_ABRV)
EXCHANGE_RATE
DATE
TABLE 2: Currency Country
CURRENCY_ABRV
CURRENCY_NAME
CURRENCY_SYMBOL
COUNTRY
REGION
COUNTRY_FLAG_IMAGE
I want to get the following information:
1. FROM_CURRENCY_FLAG
2. FROM_COUNTRY
3. TO_CURRENCY_FLAG
4. TO_COUNTRY
5. RATE
So basically using Table 1 FROM_CURRENCY & TO_CURRENCY and getting the relevant Country & Flag for each. The problem is that I cannot seem to get this info from one select statement. I at the moment I am getting all the records from Table 1. Then for each From & To currency searching Table 2.
This is very very time consuming. Anyone can help how to do this better.
Many thanks
James

Answer 1

SELECT
FROM_CURRENCY FROM_CURRENCY_FLAG,
a.COUNTRY FROM_COUNTRY,
TO_CURRENCY TO_CURRENCY_FLAG,
b.COUNTRY TO_COUNTRY,
EXCHANGE_RATE RATE
FROM TABLE1, TABLE2 a, TABLE2 b
WHERE FROM_CURRENCY = a.CURRENCY_ABRV
AND TO_CURRENCY = b.CURRENCY_ABRV;
You join TABLE1 with TABLE2 by FROM_CURRENCY and again with TABLE2 by TO_CURRENCY.
TABLE2 uses once alias name a and then alias name b, so a and b seem like different tables in the query.
All columns are assigned alias names in the SELECT clause to match your requirements.