仅用一个请求替换 2 个 SQL/ORACLE 请求

Question

我试图在一个请求中获取两个请求的结果，以下两个请求是有效的，每个请求都会生成一个包含两列的表：

SELECT patron.last_name, COUNT(*) AS **pret**
FROM circ_transaction_log INNER JOIN patron ON     circ_transaction_log.patron_id=patron.patron_id
AND **circ_transaction_log.transaction_type<5**
AND patron.college_or_school = 'High School'
GROUP BY patron.last_name;

姓氏 | pret
________________
史蒂文·格雷尔 | 552
米歇尔·文斯 | 122 ...

_______________ 或 _________________________

SELECT patron.last_name, COUNT(*) AS **resa**
FROM circ_transaction_log INNER JOIN patron ON    circ_transaction_log.patron_id=patron.patron_id
AND **circ_transaction_log.transaction_type BETWEEN 5 AND 10**
AND patron.college_or_school = 'High School'
GROUP BY patron.last_name;

姓氏 | 雷萨
________________
史蒂文·格雷尔 | 12
米歇尔·文斯 | 8
...

我想得到的结果是这样的：

姓氏 | 雷萨 | pret
______________________________
史蒂文·格雷尔 |第552章12
米歇尔·文斯 | 122 | 8
...

但我认为困难在于我请求同一个表两次计数（表 CIRC_TRANSACTION_LOG），而无论我尝试的是错误还是不工作

提前感谢您的回复

问候， 尼克

Answer 1

您可以通过使用(last_name) 的结果表的完全外部联接 组合查询。这应该会产生预期的结果。试图创建查询...

Select * from
(SELECT patron.last_name, COUNT(*) AS pret
 FROM circ_transaction_log INNER JOIN patron ON circ_transaction_log.patron_id=patron.patron_id
 AND circ_transaction_log.transaction_type<5
 AND patron.college_or_school = 'High School'
 GROUP BY patron.last_name) 
FULL OUTER JOIN
(SELECT patron.last_name, COUNT(*) AS resa
FROM circ_transaction_log INNER JOIN patron ON circ_transaction_log.patron_id=patron.patron_id
AND circ_transaction_log.transaction_type BETWEEN 5 AND 10
AND patron.college_or_school = 'High School'
GROUP BY patron.last_name) 
USING (last_name)

;

Answer 2

我更喜欢这种方法。如果该行符合您的条件，则在列中输入 1，如果不匹配，则输入 0。然后，当您将所有值相加时，它会为您提供匹配的行数。这允许您为不同的条件创建不同的总和。

SELECT
    PatronCounts.last_name,
    SUM(PatronCounts.Pret) Pret,
    SUM(PatronCounts.Resa) Resa
FROM
(SELECT 
    patron.last_name, 
    CASE WHEN circ_transaction_log.transaction_type < 5 THEN 1 ELSE 0 END AS Pret,
    CASE WHEN circ_transaction_log.transaction_type BETWEEN 5 AND 10 THEN 1 ELSE 0 END AS Resa,
FROM 
    circ_transaction_log 
    INNER JOIN patron ON circ_transaction_log.patron_id=patron.patron_id 
WHERE
    patron.college_or_school = 'High School'
GROUP BY 
    patron.last_name) PatronCounts

Answer 3

你在追求这样的东西，那么：

SELECT   p.last_name, 
         COUNT(case when ctl.transaction_type < 5 then 1 end) AS pret,
         count(case when ctl.transaction_type between 5 and 10 then 1 end) as resa
FROM     circ_transaction_log ctl
         INNER JOIN patron p ON (ctl.patron_id = p.patron_id)
AND      ctl.transaction_type <= 10  -- possibly not required if transaction_type is always <= 10 
AND      p.college_or_school = 'High School'
GROUP BY p.last_name;

注意。未经测试，因为您没有为您的表格提供任何示例数据。