哪些值使从VARCHAR到DATE的转换失败？

Question

我正在从键/值表中读取一个值，该值应包含格式的NULLABLE日期yyyy-MM-dd。

查询的简化版本是。

SELECT CAST(ClaimDate AS DATE) AS ClaimDate
FROM MyTable

这导致错误消息：

从字符串转换日期和/或时间时转换失败。

我也尝试了CONVERT(DATE, ClaimDate)无济于事。

现在，除了知道为什么会出现此错误之外，我还很想知道是哪个值导致了此错误。

我已经看到有关上述错误消息的几个问题。但是我还没有找到能回答我问题的人。

当然，除了获得不良价值外，提出解决方案也受到高度赞赏。

Answer 1

Depending on your SQL Server version (2012+), you can use TRY_CONVERT:

SELECT ClaimDate 
FROM   MyTable
WHERE  TRY_CONVERT(DATE, ClaimDate ) IS NULL
    AND ClaimDate IS NOT NULL

This will give you the values that can't be converted to a date, how you're going to solve those issues is another question. Also, a value of 2019-01-12 may be converted, but if it's in a string you cannot be sure whether this is a date in December or in January. You may get valid but wrong dates!