mysql 判斷一年有多少個星期一

SELECT
	DATE_FORMAT(
	DATE_ADD(
	CAST(
	CONCAT( YEAR ( NOW( ) ), '-01-01' ) AS date 
	),
	INTERVAL t500.id - 1 DAY 
	),
	'%w' 
	),
count(*) as days	
FROM
	t500 
WHERE
	t500.id < DATEDIFF(
	CAST(
	CONCAT(
	YEAR ( NOW( ) ) + 1,
	'-01-01' 
	) AS date 
	),
	CAST(
	CONCAT( YEAR ( NOW( ) ), '-01-01' ) AS date 
	) 
	) 
GROUP BY
	DATE_FORMAT(
	DATE_ADD(
	CAST(
	CONCAT( YEAR ( NOW( ) ), '-01-01' ) AS date 
	),
	INTERVAL t500.id - 1 DAY 
	),
	'%w' 
	)

表 t500 見 http://www.javashuo.com/article/p-ywvcvkoi-mx.html