在一个查询中组合跨表的聚合函数

Question

I am trying to build a report using SQL that will return values from completely separate tables in the same query.

I've created three queries that give me each output that I desire, but not able to get these merged into one query to generate a single report.

-- Selects count of new subscriptions from a period and their current status --

SELECT
    COUNT(
        CASE WHEN created >= '2019-05-01'
            AND created <= '2019-05-31' THEN
            1
        END) AS "number of new subscriptions",
    COUNT(
        CASE WHEN status = 'canceled'
            AND created >= '2019-05-01'
            AND created <= '2019-05-31' THEN
            1
        END) AS "count of canceled",
    COUNT(
        CASE WHEN status = 'active'
            AND created >= '2019-05-01'
            AND created <= '2019-05-31' THEN
            1
        END) AS "count of still active",
    COUNT(
        CASE WHEN status = 'trialing'
            AND created >= '2019-05-01'
            AND created <= '2019-05-31' THEN
            1
        END) AS "count of trialing",
    COUNT(
        CASE WHEN status = 'past_due'
            AND created >= '2019-05-01'
            AND created <= '2019-05-31' THEN
            1
        END) AS "count of past due"
FROM
    subscriptions;

-- Total Number of Refunds --

SELECT
        COUNT(
            CASE WHEN received_at >= '2019-05-01'
                AND received_at <= '2019-05-31'
                AND refunded = TRUE THEN
                1
            END) AS "number of refunds"
FROM
    charges;

-- Total Amount Refunded --

SELECT
    ROUND((SUM(amount_refunded) / 100), 2) AS "Total Amount Refunded"
FROM
    charges
WHERE
    received_at >= '2019-05-01'
    AND received_at <= '2019-05-31'
    AND refunded = TRUE;

I would expect the output to be the results of all individual queries merged into one output.

Answer 1

In your case you can cross join derived tables made up from your SELECT s.

SELECT *
       FROM (SELECT <rest of your first query here>) a
            CROSS JOIN (SELECT <rest of your second query here>) b
            CROSS JOIN (SELECT <rest of your third query here>) c;