嵌套的postgres查询

Question

我有两个工作查询，我似乎无法嵌套。

第一个有效：

SELECT * FROM accounts WHERE account = 'some_account';

其次很好用：

SELECT COUNT(*) FROM accounts; 

我想加入这些，以便从第一个查询的结果得到帐户的数量，它看起来像这样，但我不能这样做。

SELECT COUNT(account) FROM (SELECT * FROM accounts WHERE account = 'some_account');

我该怎么做？

Answer 1

无论

SELECT COUNT(account) 
FROM (SELECT account 
      FROM accounts 
      WHERE account = 'some_account');

或者

SELECT COUNT(*) 
FROM accounts 
WHERE account = 'some_account';

Answer 2

select count(case when account = 'some_account' then 1 else null end) as Count
FROM accounts