SQL加入更新表

Question

我有兩個表，表A有用戶標識和5個不同的產品列（空的，以count填充）。表B有時間戳用戶標識和產品標識（在時間t購買）。此代碼ID給錯誤

update table_A as table_A 
    set Count_Product_1 = (select count(product_ID) 
         from Table_B inner join Table_A 
          on Table_A.User_ID=Table_B.User_ID 
         where Product_ID = 'Unique_identifier_product_1'); 

error: You cannot reopen Table_A for update access with member-level control because Table_A is in use by you in resource environment SQL

Answer 1

我猜測你想要一個相關子查詢，不是一般的子查詢。也許這是你想要的：

update table_A as a 
    set Count_Product_1 = (select count(b.product_ID) 
          from Table_B b 
          where a.User_ID = b.User_ID and 
           b.Product_ID = 'Unique_identifier_product_1' 
         ); 

這似乎是一個更合理的查詢。