合并两个具有相同词干但不同where子句的SQL语句

Question

请帮我组合以下两条SQL语句：

SELECT Count(*) AS total_number_of_followups_scheduled
FROM PROMIS_LT; 

和 ：

SELECT Count(Status) AS number_followups_completed,  
FROM PROMIS_LT
WHERE (Status = "Completed");

这就是我所拥有的，但它不起作用：

SELECT COUNT(*) As total_number_followups_scheduled, 
COUNT(Status) 
FROM (SELECT 
CASE WHEN (Status = 'Completed' THEN 1 ELSE 0 END) As number_followups_completed FROM PROMIS_LT)
PROMIS_LT;

Answer 1

你可以移动case表达的第二个内count通话，并使用的事实， count （以及许多类似的聚合函数）跳过null S：

SELECT COUNT(*) AS total_number_of_followups_scheduled,
       COUNT(CASE status WHEN 'Completed' THEN 1 END) AS number_followups_completed
FROM   promis_lt