使用 T-SQL DATEFROMPARTS 返回 NULL 而不是抛出错误

Question

我经常以某种整数组合或单个 8 位整数的形式收到日期。为了将它们转换为可用日期，我尝试了 DATEFROMPARTS 函数，但是当日期不合理时，它会在首选 NULL 时引发错误。

我希望找到一个行为类似于 TRY_PARSE 的函数，它接受整数并为无效日期返回 NULL 而不是错误，但不需要字符串转换，因为我想在 PERSISTED 计算字段中使用它。最后，我只是决定在转换之前测试整数。

CASE WHEN @year BETWEEN 1 AND 9999 AND (@month BETWEEN 1 AND 12 AND @day BETWEEN 1 AND 28
       OR @month IN(1, 3, 5, 7, 8, 10, 12) AND @day BETWEEN 1 AND 31
       OR @month IN(4, 6, 9, 11) AND @day BETWEEN 1 AND 30
       OR @month = 2 AND @day BETWEEN 1 and CASE WHEN NOT @year % 4 = 0 THEN 28 WHEN NOT @year % 100 = 0 THEN 29 WHEN NOT @year % 400 = 0 THEN 28 ELSE 29 END)
     THEN DATEFROMPARTS(@year, @month, @day) END

这为所有 1000 万个相关整数输入（年从 0 到 9999，月从 0 到 99，日从 0 到 99）给出了日期或 NULL 我假设结果是正确的，但我还没有完成测试。有没有更好的方法可以安全地将整数输入转换为持久计算字段的日期（因此不允许字符串转换），不会引发我没有找到的错误？

Answer 1

我不确定我是否理解正确，但这可能会有所帮助：

DECLARE @year VARCHAR(100)= '1993';
DECLARE @month VARCHAR(100)= '12';
DECLARE @day VARCHAR(100)= '01';


SELECT CASE 
WHEN  ISNUMERIC(@year) = 0 OR  ISNUMERIC(@month) = 0 OR  ISNUMERIC(@day) = 0 THEN NULL
WHEN @year BETWEEN 1 AND 9999 AND (@month BETWEEN 1 AND 12 AND @day BETWEEN 1 AND 28
       OR @month IN(1, 3, 5, 7, 8, 10, 12) AND @day BETWEEN 1 AND 31
       OR @month IN(4, 6, 9, 11) AND @day BETWEEN 1 AND 30
       OR @month = 2 AND @day BETWEEN 1 and CASE WHEN NOT @year % 4 = 0 THEN 28 WHEN NOT @year % 100 = 0 THEN 29 WHEN NOT @year % 400 = 0 THEN 28 ELSE 29 END)
     THEN DATEFROMPARTS(@year, @month, @day) END;

输出：

1993-12-01

DECLARE @year VARCHAR(100)= '1993';
DECLARE @month VARCHAR(100)= 'Jan';
DECLARE @day VARCHAR(100)= '01';


SELECT CASE 
WHEN  ISNUMERIC(@year) = 0 OR  ISNUMERIC(@month) = 0 OR  ISNUMERIC(@day) = 0 THEN NULL
WHEN @year BETWEEN 1 AND 9999 AND (@month BETWEEN 1 AND 12 AND @day BETWEEN 1 AND 28
       OR @month IN(1, 3, 5, 7, 8, 10, 12) AND @day BETWEEN 1 AND 31
       OR @month IN(4, 6, 9, 11) AND @day BETWEEN 1 AND 30
       OR @month = 2 AND @day BETWEEN 1 and CASE WHEN NOT @year % 4 = 0 THEN 28 WHEN NOT @year % 100 = 0 THEN 29 WHEN NOT @year % 400 = 0 THEN 28 ELSE 29 END)
     THEN DATEFROMPARTS(@year, @month, @day) END;

输出：

空