How Can I Custom Order Currency Results in Oracle SQL?

Custom Currency Ordering in Oracle SQL

When working with transactions in different currencies, it can be useful to customize the order in which they are displayed. One common need is to have a specific currency, such as USD, always appear at the top of the list, followed by the remaining currencies in ascending order.

To achieve this in Oracle SQL, you can use the CASE or DECODE expression in the ORDER BY clause. Here's how:

CASE Expression:

ORDER BY
    CASE
        WHEN currency = 'USD' THEN 1
        WHEN currency = 'BHT' THEN 2
        WHEN currency = 'JPY' THEN 3
        WHEN currency = 'MYR' THEN 4
        ELSE 5
    END

In this example, USD is assigned a priority of 1, BHT is assigned a priority of 2, and so on. The remaining currencies are assigned a default priority of 5. The result will be sorted with USD at the top, followed by BHT, JPY, and MYR.

DECODE Expression (Oracle Specific):

ORDER BY DECODE(currency, 'USD', 1, 'BHT', 2, 'JPY', 3, 'MYR', 4, 5)

The DECODE function works similarly to the CASE expression. It takes a value (currency in this case) and matches it against a list of search conditions. If a match is found, the corresponding result is returned. Otherwise, the default value (5 in this case) is returned.

Notes:

• The priority numbers used in the CASE or DECODE expressions can be any unique values, but using sequential numbers is recommended for simplicity.

• If you want USD to appear at the top regardless of the other currencies present, you can use a character value as the priority, e.g.:

  ORDER BY
    CASE
        WHEN currency = 'USD' THEN '001'
        ELSE currency
    END

• This method assumes that you know the exact list of currencies that will appear in the result set. If there are unforeseen currencies, they will be sorted by their actual alphabetical order or numeric value, depending on the expression used.

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