Question

我有这个触发器并且它运行良好但我读到使用游标和循环对性能不利..

那么如何使用游标和循环替换一个插入语句，就像更新部分中的那个：

CREATE TRIGGER `after_insert_invoice` AFTER INSERT ON `invoicetbl`
 FOR EACH ROW BEGIN
  DECLARE v_finished INTEGER DEFAULT 0;
  DECLARE my_hour INT(11) DEFAULT 0;
  DECLARE my_day INT(11) DEFAULT 0;
  DECLARE my_month INT(11) DEFAULT 0;
  DECLARE current_item_id BINARY(16);
  DECLARE current_item_total_price DECIMAL(11, 2);
  DECLARE current_item_count DECIMAL(11, 3);

  DECLARE cur CURSOR FOR     SELECT  item_id, item_total_price, item_count
        FROM  invoice_itemtbl
        WHERE  invoice_id = NEW.invoice_id;

  DECLARE CONTINUE HANDLER FOR NOT FOUND SET v_finished = 1;

  SET my_month = EXTRACT(YEAR_MONTH FROM NEW.invoice_date);
  SET my_day = CONCAT(my_month, LPAD(DAY(NEW.invoice_date), 2, '0'));
  SET my_hour = CONCAT(my_day, LPAD(HOUR(NEW.invoice_date), 2, '0'));

  IF NEW.invoice_type = 0 THEN

        OPEN cur;

        start_loop: LOOP

        FETCH cur INTO current_item_id,
                       current_item_total_price,
                       current_item_count;

        IF v_finished = 1 THEN 
            LEAVE start_loop;
        ELSE

（续）

        INSERT
          INTO  sales_result_company_item_month(company_id, currency_id,
                time_value, item_id, result, invoices_count, item_qty )
          VALUES  (NEW.company_id, NEW.currency_id, my_month, current_item_id,
                    current_item_total_price, 1, current_item_count )
          ON DUPLICATE KEY 
          UPDATE  result = result + current_item_total_price,
                  invoices_count = invoices_count + 1,
                  item_qty = item_qty + current_item_count;

        END IF;
        END LOOP;

      CLOSE cur;

  END IF;

  IF NEW.invoice_type = 1 THEN

    //like here:
    UPDATE  sales_result_company_item_month m
    INNER JOIN  
    (
        SELECT  item_id, returns_count, returns_total
            FROM  invoice_returns
            WHERE  return_invoice_id = NEW.invoice_id
    ) f  ON m.item_id = f.item_id SET m.result = m.result - f.returns_total,
        m.item_qty = m.item_qty - f.returns_count
    WHERE  m.company_id = NEW.company_id
      AND  m.currency_id = NEW.currency_id
      AND  m.time_value = my_month;

  END IF;

END

（从注释复制 - 在'修复'问题之后，包括消除光标）：

INSERT
     INTO  sales_result_company_item_month
         (company_id, currency_id, time_value, item_id,
          result, invoices_count, item_qty) 
SELECT  NEW.company_id, NEW.currency_id, my_month, t.item_id,
        t.item_total_price, 1, t.item_count
    FROM  invoice_itemtbl t
    WHERE  invoice_id = NEW.invoice_id
    ON DUPLICATE KEY UPDATE 
        result = result + t.item_total_price,
        invoices_count = invoices_count + 1,
        item_qty = item_qty + t.item_count;

Answer 1

是的，你可以摆脱光标。

可以做

INSERT INTO t ( ... )
    ON DUPLICATE KEY UPDATE ...
    SELECT ...;

在那里，SELECT将所有行提取为“upsert”。您可能需要VALUES()子句中的UPDATE来区分所选列和表中已有的列。请参阅手册中的示例。

如果您想进一步讨论这个问题，请

为相关表提供SHOW CREATE TABLE
摆脱kruft（例如，my_day，未使用）
使用_为局部变量添加前缀，或者将它们与表列区分开来。

current_item_count DECIMAL(11, 3)让我感到困惑：什么“计数”需要3位小数？

MySQL使用一个Insert语句而不是游标循环

1 个答案: