Chapter 5 Advanced SQL Processing

Q1

SELECT product_id
,product_name
,sale_price
,MAX(sale_price) OVER (ORDER BY product_id) AS Current_max_price
FROM product

Q2

SELECT regist_date, product_name, sale_price,
       SUM(sale_price) OVER (ORDER BY COALESCE(regist_date, CAST('0001-01-01' AS DATE)))
FROM Product;

Q3

(1)排序,Add a new column to display
根据order by的排序结果,A new column is displayed by the aggregate function used
(2)selectThe purpose is to perform intra-group sorting or aggregation operations without changing the number of data items,order by 中也可用,But it doesn't actually make sense,Just sort by the field you want to sort by

Q4

-- 1.Dynamically create multiple table stored procedures：
DELIMITER $$
DROP PROCEDURE IF EXISTS world.p
CREATE DEFINER=`root`@`localhost` PROCEDURE `world`.`p`()
BEGIN
DECLARE i INT;
DECLARE table_name VARCHAR(20);
DECLARE table_pre VARCHAR(20);
DECLARE sql_text VARCHAR(2000);
SET i=1;
SET table_name='';
SET table_pre='table';
SET sql_text='';
WHILE i<21 DO
IF i<10 THEN SET table_name=CONCAT(table_pre,'0',i);
ELSE SET table_name=CONCAT(table_pre,i);
END IF;
SET sql_text=CONCAT('CREATE TABLE ', table_name, '(product_id CHAR(4) NOT NULL, product_name VARCHAR(100) NOT NULL, product_type VARCHAR(32) NOT NULL, sale_price INTEGER , purchase_price INTEGER , regist_date DATE , PRIMARY KEY (product_id))');
SELECT sql_text;
SET @sql_text=sql_text;
PREPARE stmt FROM @sql_text;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
SET i=i+1;
END WHILE;
END$$
DELIMITER ;
-- 2.执行存储过程,创建表
CALL p();