Transformation of DECODE to CASE - Example 2

decode_to_case_2.sql

-- provides percentage taxation

DECODE(tax_notice.taxtype ,'VAT',NVL(tax.vat, tax.general)
                         ,'PROP',NVL(tax.property_tax, tax.general)
                          ,'INC',NVL(tax.income_tax, tax.general)
                          ,'TAR',NVL(tax.tariff, tax.general)
                          ,tax.general)        	

-- changed to

CASE tax_notice.taxtype
    WHEN 'VAT' THEN COALESCE(tax.vat, tax.general)
    WHEN 'PROP' THEN COALESCE(tax.property_tax, tax.general)
    WHEN 'INC' THEN COALESCE(tax.income_tax, tax.general)
    WHEN 'TAR' THEN COALESCE(tax.tariff, tax.general)
    ELSE tax.general
END