How to select count of two distinct columns?

I would like to do a count of the total number of distinct COMPONENT_ID and PACKAGE_ID returned from this SQL.

开发者_运维知识库

SELECT DISTINCT COMPONENT_ID, PACKAGE_ID FROM BILL;

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You can use:

select count(distinct (COMPONENT_ID || PACKAGE_ID))
  from BILL;

Provided || is the string concatenation operator.

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select count(*)
from
(
    select distinct component_id, package_id
    from yourtable
) as distinctquery

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SELECT COUNT(*) FROM (
    SELECT DISTINCT component_id FROM bill
    UNION SELECT DISTINCT package_id FROM bill
)