使用mysql創建自己的物化視圖

　　物化視圖，它是用於預先計算並保存表連接或聚集等耗時較多的操作的結果，這樣，在執行查詢時，就可以避免進行這些耗時的操作，從而快速的得到結果。物化視圖有很多方面和索引很相似：使用物化視圖的目的是為了提高查詢性能；物化視圖對應用透明，增加和刪除物化視圖不會影響應用程序中SQL 語句的正確性和有效性；物化視圖需要占用存儲空間；當基表發生變化時，物化視圖也應當刷新

創建自己的物化視圖

DROP TABLE sales_mv;
CREATE TABLE sales_mv (
    product_name VARCHAR(128)  NOT NULL
  , price_sum    DECIMAL(10,2) NOT NULL
  , amount_sum   INT           NOT NULL
  , price_avg    FLOAT         NOT NULL
  , amount_avg   FLOAT         NOT NULL
  , sales_cnt    INT           NOT NULL
  , UNIQUE INDEX product (product_name)
);

INSERT INTO sales_mv
SELECT product_name
    , SUM(product_price), SUM(product_amount)
    , AVG(product_price), AVG(product_amount)
    , COUNT(*)
  FROM sales
GROUP BY product_name;

當有需要時對物化視圖進行刷新，存儲過程如下

DROP PROCEDURE refresh_mv_now;

DELIMITER $$

CREATE PROCEDURE refresh_mv_now (
    OUT rc INT
)
BEGIN

  TRUNCATE TABLE sales_mv;

  INSERT INTO sales_mv
  SELECT product_name
      , SUM(product_price), SUM(product_amount)
      , AVG(product_price), AVG(product_amount)
      , COUNT(*)
    FROM sales
  GROUP BY product_name;

  SET rc = 0;
END;
$$

DELIMITER ;

立刻刷新物化視圖，當執行insert，delete和update時

創建相關觸發器

DELIMITER $$

CREATE TRIGGER sales_ins
AFTER INSERT ON sales
FOR EACH ROW
BEGIN

  SET @old_price_sum = 0;
  SET @old_amount_sum = 0;
  SET @old_price_avg = 0;
  SET @old_amount_avg = 0;
  SET @old_sales_cnt = 0;

  SELECT IFNULL(price_sum, 0), IFNULL(amount_sum, 0), IFNULL(price_avg, 0)
       , IFNULL(amount_avg, 0), IFNULL(sales_cnt, 0)
    FROM sales_mv
   WHERE product_name = NEW.product_name
    INTO @old_price_sum, @old_amount_sum, @old_price_avg
       , @old_amount_avg, @old_sales_cnt
  ;

  SET @new_price_sum = @old_price_sum + NEW.product_price;
  SET @new_amount_sum = @old_amount_sum + NEW.product_amount;
  SET @new_sales_cnt = @old_sales_cnt + 1;
  SET @new_price_avg = @new_price_sum / @new_sales_cnt;
  SET @new_amount_avg = @new_amount_sum / @new_sales_cnt;

  REPLACE INTO sales_mv
  VALUES(NEW.product_name, @new_price_sum, @new_amount_sum, @new_price_avg
       , @new_amount_avg, @new_sales_cnt)
  ;

END;
$$

DELIMITER ;

DELIMITER $$

CREATE TRIGGER sales_del
AFTER DELETE ON sales
FOR EACH ROW
BEGIN

  SET @old_price_sum = 0;
  SET @old_amount_sum = 0;
  SET @old_price_avg = 0;
  SET @old_amount_avg = 0;
  SET @old_sales_cnt = 0;

  SELECT IFNULL(price_sum, 0), IFNULL(amount_sum, 0), IFNULL(price_avg, 0)
       , IFNULL(amount_avg, 0), IFNULL(sales_cnt, 0)
    FROM sales_mv
   WHERE product_name = OLD.product_name
    INTO @old_price_sum, @old_amount_sum, @old_price_avg
       , @old_amount_avg, @old_sales_cnt
  ;

  SET @new_price_sum = @old_price_sum - OLD.product_price;
  SET @new_amount_sum = @old_amount_sum - OLD.product_amount;
  SET @new_price_avg = @new_price_sum / @new_amount_sum;
  SET @new_sales_cnt = @old_sales_cnt - 1;
  SET @new_amount_avg = @new_amount_sum / @new_sales_cnt;

  REPLACE INTO sales_mv
  VALUES(OLD.product_name, @new_price_sum, @new_amount_sum
       , IFNULL(@new_price_avg, 0), IFNULL(@new_amount_avg, 0)
       , @new_sales_cnt)
  ;

END;
$$

DELIMITER ;

DELIMITER $$

CREATE TRIGGER sales_upd
AFTER UPDATE ON sales
FOR EACH ROW
BEGIN

  SET @old_price_sum = 0;
  SET @old_amount_sum = 0;
  SET @old_price_avg = 0;
  SET @old_amount_avg = 0;
  SET @old_sales_cnt = 0;

  SELECT IFNULL(price_sum, 0), IFNULL(amount_sum, 0), IFNULL(price_avg, 0)
       , IFNULL(amount_avg, 0), IFNULL(sales_cnt, 0)
    FROM sales_mv
   WHERE product_name = OLD.product_name
    INTO @old_price_sum, @old_amount_sum, @old_price_avg
       , @old_amount_avg, @old_sales_cnt
  ;

  SET @new_price_sum = @old_price_sum + (NEW.product_price - OLD.product_price);
  SET @new_amount_sum = @old_amount_sum + (NEW.product_amount
                      - OLD.product_amount);
  SET @new_sales_cnt = @old_sales_cnt;
  SET @new_price_avg = @new_price_sum / @new_sales_count;
  SET @new_amount_avg = @new_amount_sum / @new_sales_cnt;

  REPLACE INTO sales_mv
  VALUES(OLD.product_name, @new_price_sum, @new_amount_sum
       , IFNULL(@new_price_avg, 0), IFNULL(@new_amount_avg, 0)
       , @new_sales_cnt)
  ;

END;
$$

DELIMITER ;

 

 

參考：http://www.fromdual.com/mysql-materialized-views#implement