在 SQL 服务器中使用具有多个条件的 INNER JOIN

Question

I have the below data and I need to join the two tables and get the results so that it converts PRICE1_VALUE and PRICE2_VALUE to EURO in the single record.

SELECT
PRODUCT,
CASE 
        WHEN PRICE1_VALUE ='EURO'
            THEN PRICE1_VALUE
            ELSE [T1.PRICE1_VALUE]*T2.EXCHANGE_VALUE
        END AS [PRICE1_VALUE],
CASE
        WHEN PRICE2_VALUE ='EURO'
            THEN PRICE2_VALUE
            ELSE [T1.PRICE2_VALUE]*T2.EXCHANGE_VALUE
        END AS [PRICE2_VALUE],
T1.START_DATE
FROM TABLE1 T1
INNER JOIN TABLE2 T2
ON      YEAR (T1.START_DATE)= YEAR(T2.START_DATE)
AND     MONTH(T1.START_DATE)= MONTH(T2.START_DATE)
AND     (T1.PRICE1_CURRENCY= T2.FROM_CODE
    OR   T1.PRICE2_CURRENCY= T2.FROM_CODE
    )
WHERE TO_CODE = 'EURO'

With this query its returning two separate records against each record, which I can understand is because of the way I have joined the two tables. Could you please help understand how I could fix it?

I understand its this condition causing it to return multiple records.

AND     (T1.PRICE1_CURRENCY= T2.FROM_CODE
    OR   T1.PRICE2_CURRENCY= T2.FROM_CODE
    )

Answer 1

You must replace the OR-join with another join to TABLE2:

SELECT
PRODUCT,
CASE 
        WHEN PRICE1_VALUE ='EURO'
            THEN PRICE1_VALUE
            ELSE [T1.PRICE1_VALUE]*T2.EXCHANGE_VALUE
        END AS [PRICE1_VALUE],
CASE
        WHEN PRICE2_VALUE ='EURO'
            THEN PRICE2_VALUE
            ELSE [T1.PRICE2_VALUE]*T3.EXCHANGE_VALUE
        END AS [PRICE2_VALUE],
T1.START_DATE
FROM TABLE1 T1
INNER JOIN TABLE2 T2 -- maybe LEFT JOIN
ON      YEAR (T1.START_DATE)= YEAR(T2.START_DATE)
AND     MONTH(T1.START_DATE)= MONTH(T2.START_DATE)
AND     T1.PRICE1_CURRENCY= T2.FROM_CODE
INNER JOIN TABLE2 T3 -- maybe LEFT JOIN
ON      YEAR (T1.START_DATE)= YEAR(T3.START_DATE)
AND     MONTH(T1.START_DATE)= MONTH(T3.START_DATE)
AND     T1.PRICE2_CURRENCY= T3.FROM_CODE

Answer 2

If I understand correctly, you can do what you want with two left join s:

SELECT PRODUCT,
       (CASE WHEN PRICE1_CURRENCY ='EURO'
             THEN PRICE1_VALUE
              ELSE T1.PRICE1_VALUE * T2_1.EXCHANGE_VALUE
        END) AS PRICE1_VALUE,
       (CASE WHEN PRICE2_CURRENCY = 'EURO'
             THEN PRICE2_VALUE
             ELSE T1.PRICE2_VALUE * T2_2.EXCHANGE_VALUE
        END ) AS PRICE2_VALUE
       T1.START_DATE
FROM TABLE1 T1 LEFT JOIN
     TABLE2 T2_1
     ON YEAR(T1.START_DATE) = YEAR(T2_1.START_DATE) AND
        MONTH(T1.START_DATE) = MONTH(T2_1.START_DATE) AND
        T1.PRICE1_CURRENCY = T2_1.FROM_CODE LEFT JOIN
     TABLE2 T2_2
     ON YEAR(T1.START_DATE) = YEAR(T2_2.START_DATE) AND
        MONTH(T1.START_DATE) = MONTH(T2_2.START_DATE) AND
        T1.PRICE2_CURRENCY = T2_2.FROM_CODE 
WHERE T2_1.FROM_CODE IS NOT NULL OR T2_2.FROM_CODE IS NOT NULL;

Note: Do not overuse square braces. Your use looked incorrect in your code and was unnecessary.

Answer 3

I don't think your query is doing what you want it to.

The specific answer to your question - "Why do I get two results?" is that the OR clause matches a the "1 to 1" conversion row in your table:

OR T1.PRICE2_CURRENCY= T2.FROM_CODE

A better version of your query would be:

SELECT
PRODUCT,
T1.PRICE1_VALUE *P1_CONVERSION_RATE.EXCHANGE_VALUE AS [PRICE1_VALUE],
T1.PRICE2_VALUE *P2_CONVERSION_RATE.EXCHANGE_VALUE AS [PRICE2_VALUE],
T1.START_DATE
FROM TABLE1 T1
INNER JOIN TABLE2 P1_CONVERSION_RATE
ON      YEAR (T1.START_DATE)= YEAR(T2.START_DATE)
AND     MONTH(T1.START_DATE)= MONTH(T2.START_DATE)
AND     T1.PRICE1_CURRENCY= T2.FROM_CODE
INNER JOIN TABLE2 P2_CONVERSION_RATE
ON      YEAR (T1.START_DATE)= YEAR(T2.START_DATE)
AND     MONTH(T1.START_DATE)= MONTH(T2.START_DATE)
AND     T1.PRICE2_CURRENCY= T2.FROM_CODE

Answer 4

If you want EURO as a result only, you can just add in the end:

where T2.TO_CODE='EURO'

However, if you want to see both prices for each product, stick to Gordon's solution.

Answer 5

you can do using distinct

SELECT  distinct
PRODUCT,
CASE 
        WHEN PRICE1_VALUE ='EURO'
            THEN PRICE1_VALUE
            ELSE [T1.PRICE1_VALUE]*T2.EXCHANGE_VALUE
        END AS [PRICE1_VALUE],
CASE
        WHEN PRICE2_VALUE ='EURO'
            THEN PRICE2_VALUE
            ELSE [T1.PRICE2_VALUE]*T2.EXCHANGE_VALUE
        END AS [PRICE2_VALUE],
T1.START_DATE
FROM TABLE1 T1
INNER JOIN TABLE2 T2
ON      YEAR (T1.START_DATE)= YEAR(T2.START_DATE)
AND     MONTH(T1.START_DATE)= MONTH(T2.START_DATE)
AND     (T1.PRICE1_CURRENCY= T2.FROM_CODE
    OR   T1.PRICE2_CURRENCY= T2.FROM_CODE
    )