SQL中CAST和CONVERT用在时间转换上的区别（我新手，越详细越好）

Posted 2023-03-21

还有他们是不是用在时间的转换上比较多！不要到网上复制粘贴（谢谢合作）BS不劳而获的，没有满意答案，会关闭问题有满意答案会追加200分给你

参考技术A cast 和convert都是用来转化数据类型的，功能上是差不多的。
表达式：CAST ( expression AS data_type ) ，
CONVERT (data_type[(length)], expression [, style])，
在时间转化中一般用到convert,因为它比cast多加了一个style,可以转化成不同时间的，打个简单的例子吧，比方说查找一下当前的时间，select getdate(),而我们只需要到年月日而已，这时我们就可以把它转化为select convert(varchar(100),GETDATE(),111)转化成我们需要的，而select CAST(GETDATE() as varchar(30))cast就没办法或者是转化过程比较繁琐，convert时间后面的style值不同产生的时间格式也不一样，具体可参看网站http://www.w3school.com.cn/sql/func_convert.asp本回答被提问者采纳 参考技术B CONVERT 与 CAST 都可以 用来做 字符 与 日期 类型之间的转换。
但是一般来说， 用 CONVERT 比较好， 因为有一个 用于格式化的参数。

你执行一下下面这个 SQL， 就能看出区别出来。

SELECT 0 AS ID , Convert(VARCHAR(30), GETDATE(), 0 ) AS result UNION ALL
SELECT 100 AS ID , Convert(VARCHAR(30), GETDATE(), 100) AS result UNION ALL
SELECT 1 AS ID , Convert(VARCHAR(30), GETDATE(), 1 ) AS result UNION ALL
SELECT 101 AS ID , Convert(VARCHAR(30), GETDATE(), 101) AS result UNION ALL
SELECT 2 AS ID , Convert(VARCHAR(30), GETDATE(), 2 ) AS result UNION ALL
SELECT 102 AS ID , Convert(VARCHAR(30), GETDATE(), 102) AS result UNION ALL
SELECT 2 AS ID , Convert(VARCHAR(30), GETDATE(), 2 ) AS result UNION ALL
SELECT 102 AS ID , Convert(VARCHAR(30), GETDATE(), 102) AS result UNION ALL
SELECT 3 AS ID , Convert(VARCHAR(30), GETDATE(), 3 ) AS result UNION ALL
SELECT 103 AS ID , Convert(VARCHAR(30), GETDATE(), 103) AS result UNION ALL
SELECT 4 AS ID , Convert(VARCHAR(30), GETDATE(), 4 ) AS result UNION ALL
SELECT 104 AS ID , Convert(VARCHAR(30), GETDATE(), 104) AS result UNION ALL
SELECT 5 AS ID , Convert(VARCHAR(30), GETDATE(), 5 ) AS result UNION ALL
SELECT 105 AS ID , Convert(VARCHAR(30), GETDATE(), 105) AS result UNION ALL
SELECT 6 AS ID , Convert(VARCHAR(30), GETDATE(), 6 ) AS result UNION ALL
SELECT 106 AS ID , Convert(VARCHAR(30), GETDATE(), 106) AS result UNION ALL
SELECT 7 AS ID , Convert(VARCHAR(30), GETDATE(), 7 ) AS result UNION ALL
SELECT 107 AS ID , Convert(VARCHAR(30), GETDATE(), 107) AS result UNION ALL
SELECT 8 AS ID , Convert(VARCHAR(30), GETDATE(), 8 ) AS result UNION ALL
SELECT 108 AS ID , Convert(VARCHAR(30), GETDATE(), 108) AS result UNION ALL
SELECT 9 AS ID , Convert(VARCHAR(30), GETDATE(), 9 ) AS result UNION ALL
SELECT 109 AS ID , Convert(VARCHAR(30), GETDATE(), 109) AS result UNION ALL
SELECT 10 AS ID , Convert(VARCHAR(30), GETDATE(), 10 ) AS result UNION ALL
SELECT 110 AS ID , Convert(VARCHAR(30), GETDATE(), 110) AS result UNION ALL
SELECT 11 AS ID , Convert(VARCHAR(30), GETDATE(), 11 ) AS result UNION ALL
SELECT 111 AS ID , Convert(VARCHAR(30), GETDATE(), 111) AS result UNION ALL
SELECT 12 AS ID , Convert(VARCHAR(30), GETDATE(), 12 ) AS result UNION ALL
SELECT 112 AS ID , Convert(VARCHAR(30), GETDATE(), 112) AS result UNION ALL
SELECT 13 AS ID , Convert(VARCHAR(30), GETDATE(), 13 ) AS result UNION ALL
SELECT 113 AS ID , Convert(VARCHAR(30), GETDATE(), 113) AS result UNION ALL
SELECT 14 AS ID , Convert(VARCHAR(30), GETDATE(), 14 ) AS result UNION ALL
SELECT 114 AS ID , Convert(VARCHAR(30), GETDATE(), 114) AS result UNION ALL
SELECT 20 AS ID , Convert(VARCHAR(30), GETDATE(), 20 ) AS result UNION ALL
SELECT 120 AS ID , Convert(VARCHAR(30), GETDATE(), 120) AS result UNION ALL
SELECT 21 AS ID , Convert(VARCHAR(30), GETDATE(), 21 ) AS result UNION ALL
SELECT 121 AS ID , Convert(VARCHAR(30), GETDATE(), 121) AS result 参考技术C
参考技术D