SQL 检查值是否为日期并将其转换
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Check if value is date and convert it
提问by Inus C
I receive data in a certain format. Dates are numeric(8,0). For example 20120101 = YYYYMMDD
我以某种格式接收数据。日期是数字（8,0）。例如20120101 = YYYYMMDD
There exists rows with values like (0,1,2,3,6)in that date field, thus not a date.
存在具有与(0,1,2,3,6)该日期字段类似的值的行，因此不是日期。
I want to check if it is a date and convert it, else it can be null.
我想检查它是否是日期并将其转换，否则它可以为空。
Now the following code works, but I was hoping there is a better way.
现在以下代码有效，但我希望有更好的方法。
(CASE WHEN [invoice_date] LIKE '________' --There are 8 underscores
THEN convert(datetime, cast([invoice_date] as char(8)))
END) AS Invoice_Date
Any help will be appreciated.
任何帮助将不胜感激。
回答by Deniyal Tandel
use isdate function like ..
使用 isdate 函数，如 ..
(CASE WHEN ISDATE (invoice_date) = 1
THEN convert(datetime, cast([invoice_date] as char(8)))
END) AS Invoice_Date
回答by von v.
You can use the ISDATE function, but what would do for non-date values? In my suggested solution you can choose to return a null:
您可以使用 ISDATE 函数，但是对于非日期值会怎样呢？在我建议的解决方案中，您可以选择返回空值：
select
(case
when ISDATE (invoice_date)=1
then convert(datetime, invoice_date)
else null end) AS Invoice_Date
from your_table
回答by von v.
ISDATE
伊斯达特
Returns 1 if the expression is a valid date, time, or datetime value; otherwise, 0. ISDATE returns 0 if the expression is a datetime2 value.
如果表达式是有效的日期、时间或日期时间值，则返回 1；否则，0。如果表达式是 datetime2 值，ISDATE 返回 0。
回答by kiriloff
You can go with TRYCATCH
你可以去 TRYCATCH
DECLARE @Source char(8)
DECLARE @Destination datetime
set @Source='07152009'
BEGIN TRY
SET @Destination=CONVERT(datetime,RIGHT(@Source,4) -- YYYY
+LEFT(@Source,2) -- MM
+SUBSTRING(@Source,3,2) -- DD
)
END TRY
BEGIN CATCH
PRINT 'ERROR!!!'
END CATCH
SELECT @Source AS Source, @Destination AS Destination
