在 SQL Server 中将字符串日期转换为 GETDATE() 格式

Question

We have a table employee with columns LastUpdated (datetime) , ExitDate (datetime) and ReleaseDate (varchar(50)) .

The date in the table is shown here:

+-------------------------+----------------------+
|       LastUpdated       |     ReleaseDate      |
+-------------------------+----------------------+
| 2019-05-24 01:19:21.597 | 4/8/2016 7:00:00 AM  |
| 2019-05-24 02:05:26.130 | 3/20/2007 7:00:00 AM |
| 2019-05-24 01:57:44.810 | 5/14/2007 7:00:00 AM |
| 2019-05-24 01:48:40.483 | 3/16/2010 7:00:00 AM |
| 2019-05-24 01:11:41.290 | 11/8/2018 8:00:00 AM |
+-------------------------+----------------------+

Now I want to convert the ReleaseDate column values into the LastUpdated column format ( yyyy-MM-dd HH:mm:ss ) and update the value to the column ExitDate .

The LastUpdated column value was inserted using GETDATE() in SQL Server.

Can anyone help with this, please?

Answer 1

You can use update :

update employee
     set ExitDate = convert(datetime, ReleaseDate, 101);

However, storing date value into other format not a good practice.

Answer 2

You can parse the string to a date, then convert the date to a string in the desired format. The string formats supported for datetime conversions are documented here .

So something like:

update employee set ReleaseDate = convert(varchar(50), convert(datetime,ReleaseDate, 101), 121);

if all the rows are in the same date format. If the date format varies, you can try:

update employee set ReleaseDate = convert(varchar(50), convert(datetime,ReleaseDate), 121);

to convert using the your current culture settings and SQL Server's permissive conversion rules.

But you should then alter the column's datatype, if, and when that is possible:

alter table employee alter column ReleaseDate datetime

or add a check constraint to force the application to make sure no other format is inserted.

alter table employee add constraint [ck_EnforceReleaseDateFormat_YYYY-MM-DD HH:MM:SS]
check (ReleaseDate = convert(varchar(50), convert(datetime,ReleaseDate, 121), 121))