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建立透視表t500

建表

CREATE TABLE `t500` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=501 DEFAULT CHARSET=latin1;

插入500條資料

CREATE DEFINER=`json`@`%` PROCEDURE `i500`()
BEGIN 
 DECLARE a INT default 1;
 while a<=500 do
 insert into t500 (id) value(a);
 set a=a+1;
 end while;
 end
 

2.1

select t500.id from t500 where t500.id <=DATEDIFF("2019-02-01","2019-01-01")+1

2.2

SELECT
	DATE_ADD(
	STR_TO_DATE( "2019-01-01", '%Y-%m-%d' ),
	INTERVAL t500.id - 1 DAY 
	) 
FROM
	t500 
WHERE
	t500.id <= DATEDIFF( "2019-02-01", "2019-01-01" ) +1

2.3

SELECT
	DATE_FORMAT(
	DATE_ADD(
	STR_TO_DATE( "2019-01-01", '%Y-%m-%d' ),
	INTERVAL t500.id - 1 DAY 
	),
	'%a' 
	) 
FROM
	t500 
WHERE
	t500.id <= DATEDIFF( "2019-02-01", "2019-01-01" ) +1
 

2.4

	SELECT
CASE
	
WHEN
	DATE_FORMAT(
	DATE_ADD(
STR_TO_DATE( "2019-01-01", '%Y-%m-%d' ),
	INTERVAL t500.id - 1 DAY 
	),
	'%a' 
	) IN ( 'Sat', 'Sun' ) THEN
		0 ELSE 1 end 
	FROM
		t500 
WHERE
t500.id <= DATEDIFF( "2019-02-01", "2019-01-01" ) +1

2.5 最終SQL

select sum(CASE
	
WHEN
	DATE_FORMAT(
	DATE_ADD(
STR_TO_DATE( "2019-01-01", '%Y-%m-%d' ),
	INTERVAL t500.id - 1 DAY 
	),
	'%a' 
	) IN ( 'Sat', 'Sun' ) THEN
		0 ELSE 1 end ) as days from 
		t500 
WHERE
t500.id <= DATEDIFF( "2019-02-01", "2019-01-01