MySQL stored procedure exercise

Exercises ：

1. Create a table corresponding to each day of the next month user_2022_08_01、user_2022_08_2、…

Preliminary knowledge

PREPARE stmt_name FROM preparable_stmt
EXECUTE stmt_name [USING @var_name [,@var_name]…]
{DEALLOCATE || DROP} PREPARE stmt_name
Knowledge point Time processing
EXTRACRT(unit FROM date) The specified location value of the interception time
DATE ADD(date,INTERVAL expr unit) Date operations
LAST DAY(date) Get the last day of the date
YEAR(date) Returns the year in the date
MONTH(date) Returns the month of the date
DAYOFMONTH(date) Return day

The answer to the exercise

DELIMITER $$
CREATE PROCEDURE proc22_demo()
BEGIN
DECLARE next_year INT; --  The year of the next month 
DECLARE next_month INT; --  Month of next month 
DECLARE next_month_day INT; --  The date of the last day of the next month 

DECLARE next_month_str VARCHAR(2); --  The month string of the next month 
DECLARE next_month_day_str VARCHAR(2); --  Next month's Day string 

--  Process daily table names 
DECLARE table_name_str VARCHAR(10);
DECLARE t_index INT DEFAULT 1;

--  Get the year of the next month 
SET next_year = YEAR(DATE_ADD(NOW(),INTERVAL 1 MONTH));
--  Get what month is next 
SET next_month =MONTH(DATE_ADD(NOW(),INTERVAL 1 MONTH));
--  What is the last day of next month 
SET next_month_day = DAYOFMONTH(LAST_DAY(DATE_ADD(NOW(),INTERVAL 1 MONTH)));

IF next_month < 10 
THEN SET next_month_str = CONCAT('0',next_month);
ELSE
SET next_month_str = CONCAT('',next_month);
END IF;

WHILE t_index <= next_month_day DO
IF (t_index < 10)
	THEN SET next_month_day_str = CONCAT('0',t_index);
ELSE
	SET next_month_day_str = CONCAT('',t_index);
END IF;
	
	SET table_name_str = CONCAT(next_year,'_',next_month_str,'_',next_month_day_str);
-- 	 Splicing create sql sentence 
SET @create_table_sql = CONCAT(
'create table user_',
table_name_str,
'(`uid` INT ,`uname` varchar(50) ,`information` varchar(50)) COLLATE=\'utf8_general_ci\' ENGINE=InnoDB');
-- FROM Local variables cannot be used later 
PREPARE create_table_stmt FROM @create_table_sql;
EXECUTE create_table_stmt;
DEALLOCATE PREPARE create_table_stmt;

SET t_index = t_index + 1;

END WHILE;

END $$
DELIMITER ;
CALL proc22_demo();