How to Custom Order Data by Currency with USD Priority in Oracle SQL?

Custom Order with Currency Preference in Oracle SQL

Many data querying tasks involve ordering data based on specific criteria. When the desired order deviates from standard alphabetical or numerical arrangements, a custom order becomes necessary. This article discusses a scenario where transactions need to be ordered based on the currency, with a specific preference for placing USD at the top.

To achieve this custom order, Oracle SQL provides two approaches:

• CASE Expression: Using a CASE expression, you can assign numerical values to each currency based on its priority. For example:

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

This expression assigns a value of 1 to USD, ensuring that it appears first, followed by the other currencies in the specified order.

• DECODE Function: Oracle's DECODE function offers a more compact alternative to the CASE expression. It allows you to assign values based on specific conditions:

order by decode(currency, 'USD', 1, 'BHT', 2, 'JPY', 3, 'MYR', 4, 5)

Here, DECODE checks the currency value and returns the corresponding numerical priority.

Note: While these methods work for the currencies provided in the question, they may not sort other currencies correctly if they are not explicitly included in the CASE or DECODE statements.

Additional Customization: If you only want to prioritize USD, treating all other currencies equally, you can use the following technique:

order by 
    case 
       when currency = 'USD' then '001' 
       else currency
    end

This expression assigns a unique character string ('001') to USD, which will appear first in the alphabetical ordering due to its lower ASCII value.

By employing these methods, you can customize the order of data based on specific criteria, providing flexible and powerful solutions in Oracle SQL.

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