Summarizing two conditions on the same SQL table

问题

Given a SQL table

Transactions
  ID            INT
  COMPANY_ID    INT
  STATUS        INT

where STATUS IN (0,1) indicates a free transaction and STATUS IN (2,3) indicates a billable transaction, what simple (I hope) ANSI SQL statement will show me, per COMPANY_ID, the number of billable transactions, non-billable transactions, and their ratio?

A conceptual prod in the right direction is fine if not a specific statement. My first attempts are to self-join on the table with WHERE clauses for the two status groups, but I'm stuck at how to get a column representing each distinct count so that I can compute the ratio.

This is conceptually very similar to summarize-aggregated-data but I'm not sure how to extend that question to this one.

回答1:

Here is a start, I think this is along the right lines...The only thing left would be to add the ratio.

SELECT
    COMPANY_ID,
    NON_BILLABLE = SUM(CASE STATUS WHEN IN (0, 1) THEN 1 ELSE 0 END),
    BILLABLE = SUM(CASE STATUS WHEN IN (2, 3) THEN 1 ELSE 0 END)
FROM TRANSACTIONS
GROUP BY COMPANY_ID

EDIT: for standards compliance.

SELECT
    COMPANY_ID,
    SUM(CASE STATUS WHEN IN (0, 1) THEN 1 ELSE 0 END) AS NON_BILLABLE,
    SUM(CASE STATUS WHEN IN (2, 3) THEN 1 ELSE 0 END) AS BILLABLE
FROM TRANSACTIONS
GROUP BY COMPANY_ID

来源：https://stackoverflow.com/questions/1786987/summarizing-two-conditions-on-the-same-sql-table