SQL | 将两个查询的结果合并到一张表中

Question

I'm new to SQL....

I have a table in which one column, "status", has a list of approved/declined orders. How do I write a query that gives the result of two columns: 'Total Approved Orders', 'Total Orders' in one table?

I know how to pull these results in two separate queries, ie:

SELECT COUNT(status) FROM orders WHERE status = 'Approved';

SELECT COUNT(status) FROM orders;

But unsure how this is done for one table/result

Answer 1

You can do conditional aggregation:

select
    sum(case when status = 'Approved' then 1 else 0 end) total_orders_approved,
    count(*) total_orders
from orders

Depending on your database, there might be shorter syntaxes available. In MySQL:

select
    sum(status = 'Approved') total_orders_approved,
    count(*) total_orders
from orders

In Postgres:

select
    Count(*) filter(where status = 'Approved') total_orders_approved,
    count(*) total_orders
from orders

Answer 2

You can combine these as sub queries as follows;

SELECT
(SELECT COUNT(status) FROM orders WHERE status = 'Approved') AS 'Approved',
(SELECT COUNT(status) FROM orders) AS 'All Orders
;