CREATE DEFINER=`root`@`localhost` FUNCTION `rand_string`(n INT) RETURNS varchar(255) CHARSET latin1
BEGIN
	DECLARE chars_str 	varchar(100) DEFAULT 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz';
  DECLARE return_str 	varchar(255) DEFAULT '';
  DECLARE i INT DEFAULT 0;
  WHILE i < n DO
    SET return_str = concat(return_str,substring(chars_str , FLOOR(1 + RAND()*62 ),1));
    SET i = i +1;
  END WHILE;
  RETURN return_str;
END

show function status

select rand_string(5);

SELECT
	date(
	from_unixtime( unix_timestamp( '2000-01-01' ) + floor( rand() * ( unix_timestamp( '2020-12-31' ) - unix_timestamp( '2000-01-01' ) + 1 ) ) ));

CREATE DEFINER=`root`@`localhost` FUNCTION `rand_date_string`(startDate varchar(255),endDate varchar(255)) RETURNS varchar(255) CHARSET latin1
BEGIN
  DECLARE return_str varchar(255) DEFAULT '';
	
	 SET return_str =date(
		from_unixtime( unix_timestamp( startDate ) 
				+ floor( rand() * ( unix_timestamp( endDate ) - unix_timestamp( startDate ) + 1 ) ) 
			)
	 );
  
  RETURN return_str;
END

select rand_date_string('2000-01-01','2020-12-31');
//結(jié)果
2001-09-10

CREATE DEFINER=`root`@`localhost` PROCEDURE `data`()
BEGIN
	
	DECLARE i INT DEFAULT 1;
	DECLARE j INT DEFAULT 0;
	DECLARE id INT DEFAULT 0;
	WHILE i < 10 DO
			WHILE j < 1000000 DO
				insert into employees_m (emp_no,birth_date,first_name,last_name,gender,hire_date) VALUES(
					id,rand_date_string('1970-01-01','1997-01-01'),rand_string(5),rand_string(5),'M',NOW());
				
				insert into dept_emp_m (emp_no,dept_no,from_date,to_date) values(
					 id,concat('d00',i),rand_date_string('1990-01-01','2020-12-31'),'2020-12-31');
					 
			SET j=j+1;  
			SET id=id+1;  
			END WHILE;
	SET j = 0;
	SET i=i+1;   
	END WHILE;

END

ALTER TABLE dept_emp_m ENGINE=MEMORY;

[mysqld]
max_heap_table_size = 2048M
tmp_table_size = 2048M