C++ SQLITE：如何在update语句中使用SELECT语句更新表？

我有以下2015年付款表：

ref-no  |Jan    |Feb    |Mar   |Apr    |May     |Jun
1       |       |PAID   |PAID  |       |PAID    |  
2       |       |PAID   |      |       |        |PAID
3       |PAID   |       |PAID  |PAID   |PAID    |PAID
4       |PAID   |PAID   |      |PAID   |PAID    |
5       |PAID   |       |PAID  |       |        |
6       |       |       |      |       |        |PAID 

我正在使用以下查询检查每个参考号有多少个月未支付：

for(int i = 0; i < all_refNo_list.size(); i++) {
        qryTxt = "INSERT INTO late_payments "
                "select ref_no AS ref_no, sum(i_count) as unpaid_count from ("
                "SELECT ref_no, CASE WHEN January = 'PAID' THEN 0 ELSE 1 END AS i_count, 1 AS month_no FROM payments_" + getCurrentYear() +
                " UNION SELECT ref_no, CASE WHEN February = 'PAID' THEN 0 ELSE 1 END , 2  FROM payments_" + getCurrentYear() +
                " UNION SELECT ref_no, CASE WHEN March = 'PAID' THEN 0 ELSE 1 END , 3  FROM payments_" + getCurrentYear() +
                " UNION SELECT ref_no, CASE WHEN April = 'PAID' THEN 0 ELSE 1 END , 4  FROM payments_" + getCurrentYear() +
                " UNION SELECT ref_no, CASE WHEN May = 'PAID' THEN 0 ELSE 1 END , 5  FROM payments_" + getCurrentYear() +
                " UNION SELECT ref_no, CASE WHEN June = 'PAID' THEN 0 ELSE 1 END , 6  FROM payments_" + getCurrentYear() +
                " UNION SELECT ref_no, CASE WHEN July = 'PAID' THEN 0 ELSE 1 END , 7  FROM payments_" + getCurrentYear() +
                " UNION SELECT ref_no, CASE WHEN August = 'PAID' THEN 0 ELSE 1 END , 8  FROM payments_" + getCurrentYear() +
                " UNION SELECT ref_no, CASE WHEN September = 'PAID' THEN 0 ELSE 1 END , 9  FROM payments_" + getCurrentYear() +
                " UNION SELECT ref_no, CASE WHEN October = 'PAID' THEN 0 ELSE 1 END , 10  FROM payments_" + getCurrentYear() +
                " UNION SELECT ref_no, CASE WHEN November = 'PAID' THEN 0 ELSE 1 END , 11  FROM payments_" + getCurrentYear() +
                " UNION SELECT ref_no, CASE WHEN December = 'PAID' THEN 0 ELSE 1 END , 12  FROM payments_" + getCurrentYear() +
                ") A Where ref_no = " + all_refNo_list[i];

        query.prepare(qryTxt);
        if (!query.exec())
        {
            qDebug() << "Error" << query.lastError().text();
        }
    }

现在，如果我在1月份为ref_no=1插入“PAID”，结果仍然相同。当然，它将保持不变，因为我插入的是已经存在的记录，而不是更新

每当某个月被检查为“已支付”特定“参考号”时，我无法更新这些值。i、 e:只要有变化，就更新表格

更新：

我尝试了以下方法：

for(int i = 0; i < getAllRefNoList().size(); i++) { 
qryTxt = "UPDATE late_payments "
                "SET unpaid_count = ("
                "select sum(i_count) as unpaid_count from ("
                "SELECT CASE WHEN January = 'PAID' THEN 0 ELSE 1 END AS i_count, 1 AS month_no FROM payments_" + getCurrentYear() +
                " UNION SELECT CASE WHEN February = 'PAID' THEN 0 ELSE 1 END , 2  FROM payments_" + getCurrentYear() +
                " UNION SELECT CASE WHEN March = 'PAID' THEN 0 ELSE 1 END , 3  FROM payments_" + getCurrentYear() +
                " UNION SELECT CASE WHEN April = 'PAID' THEN 0 ELSE 1 END , 4  FROM payments_" + getCurrentYear() +
                " UNION SELECT CASE WHEN May = 'PAID' THEN 0 ELSE 1 END , 5  FROM payments_" + getCurrentYear() +
                " UNION SELECT CASE WHEN June = 'PAID' THEN 0 ELSE 1 END , 6  FROM payments_" + getCurrentYear() +
                " UNION SELECT CASE WHEN July = 'PAID' THEN 0 ELSE 1 END , 7  FROM payments_" + getCurrentYear() +
                " UNION SELECT CASE WHEN August = 'PAID' THEN 0 ELSE 1 END , 8  FROM payments_" + getCurrentYear() +
                " UNION SELECT CASE WHEN September = 'PAID' THEN 0 ELSE 1 END , 9  FROM payments_" + getCurrentYear() +
                " UNION SELECT CASE WHEN October = 'PAID' THEN 0 ELSE 1 END , 10  FROM payments_" + getCurrentYear() +
                " UNION SELECT CASE WHEN November = 'PAID' THEN 0 ELSE 1 END , 11  FROM payments_" + getCurrentYear() +
                " UNION SELECT CASE WHEN December = 'PAID' THEN 0 ELSE 1 END , 12  FROM payments_" + getCurrentYear() +
                ") A WHERE ref_no = " + getAllRefNoList()[i] + ")";

        query.prepare(qryTxt);
        if (!query.exec())
        {
            qDebug() << "Error" << query.lastError().text();
        }

但是没有成功

---

S.S:我在Qt上为C++应用程序实现这些选择语句。我正在使用QSqlQueryModel在QTableView上显示select语句的结果。

select语句的更新语句是：

UPDATE A
    SET COUNT = <your value>
WHERE ref_no = 1

---

select语句的Update语句为：

UPDATE A
    SET COUNT = <your value>
WHERE ref_no = 1

---

看起来你们这里有两张桌子。一种方法是：

update b
    set count = (select count from a where ref_no = 1);

---

这将更新b中的所有行。您的问题没有建议将其限制为一行或几行。

这里似乎有两个表。一种方法是：

update b
    set count = (select count from a where ref_no = 1);

---

这将更新b中的所有行。您的问题不建议将其限制为一行或几行。

首先，创建一个查询以计算所需的表：

SELECT refno,
       (ifnull(Jan, '') != 'PAID') +
       (ifnull(Feb, '') != 'PAID') +
       ...
       (ifnull(Dec, '') != 'PAID) AS unpaid_count
FROM payments_2015;

然后，您可以删除该表，而是使用动态生成这些结果的视图：

CREATE VIEW late_payments_2015 AS
SELECT ...;

---

首先，创建一个查询来计算所需的表：

SELECT refno,
       (ifnull(Jan, '') != 'PAID') +
       (ifnull(Feb, '') != 'PAID') +
       ...
       (ifnull(Dec, '') != 'PAID) AS unpaid_count
FROM payments_2015;

然后，您可以删除该表，而是使用动态生成这些结果的视图：

CREATE VIEW late_payments_2015 AS
SELECT ...;

---

你的更新有效吗？你有什么错误？您还尝试了什么？您的select语句返回两个值，但您只想更新一个-尝试从WHERE ref_no=1中选择计数。尝试使用update B SET count=select count从WHERE ref_no=1中选择计数作为cW更改是什么意思？@CL。。我的意思是，每当2015年付款表发生变化时，逾期付款应反映新的变化，并更新“未付金额”列。您的更新有效吗？你有什么错误？您还尝试了什么？您的select语句返回两个值，但您只想更新一个-尝试从WHERE ref_no=1中选择计数。尝试使用update B SET count=select count从WHERE ref_no=1中选择计数作为cW更改是什么意思？@CL。。我的意思是，每当2015年付款表发生变化时，逾期付款应反映新的变化，并更新“未付金额”列。谢谢您的回答。但是，我知道UPDATE语句语法。这是在同一个查询中混合使用SELECT和UPDATE的问题，这是一个SELECT语句，但是您的解决方案不起作用。谢谢您的回答。但是，我知道UPDATE语句语法。这是在同一个查询中混合使用SELECT和UPDATE，这是我正在努力解决的问题。。下面是SELECT语句，但您的解决方案不起作用。您是对的，我没有指定行数。请查看问题更新以了解更多解释。很抱歉，您的回答不起作用，因为我有两个级别的SELECT语句。答案中的a是另一个SELECT语句。您是对的，我没有指定行数。请查看问题更新以了解更多解释。很抱歉，您的回答不起作用，因为我有两个级别的SELECT语句。你的答案中的a是另一个精选语句。非常感谢。。你的陈述比我的更容易写和理解…非常感谢。。你的陈述比我的更容易写和理解。。。