SQLITE：如何在UPDATE語句中使用SELECT語句更新表？

Question

我有以下payments_2015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 

我檢查每個ref_no多少個月使用下面的查詢不支付：

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(); 
     } 
    } 

結果如下late_payments表：

ref_no |unpaid_count 
1  |3 
2  |4 
3  |1 
4  |2 
5  |4 
6  |5 

現在，如果我在1月爲ref_no = 1插入'PAID'，結果仍然相同。當然，它會保持不變，因爲我插入已經存在的記錄而不是更新。

對於特定的'ref_no'，每月檢查爲'PAID'時，我無法更新這些值。即：只要有變化就更新表格。

UPDATE：

我已經試過如下：

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(); 
     } 

但沒有成功..

PS：我實現了一個C Qt的這些選擇語句++應用。我使用QSqlQueryModel在QTableView上顯示選擇語句的結果。

Answer 1

首先，創建一個查詢計算所需的表：

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

然後你就可以刪除該表，而是使用產生這些結果動態視圖：

CREATE VIEW late_payments_2015 AS 
SELECT ...; 

Answer 2

爲你的SELECT語句UPDATE語句：

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

Answer 3

它看起來就像你有兩個表在這裏。一種方法是：

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

這將更新b中的所有行。你的問題並沒有建議任何方式將其限制爲一行或幾行。