T-SQL在现有表中添加新列，并从另一个现有列填充值

Question

I have a table test with the following columns: id , startDate , stopDate , startOvertime , stopOvertime .

startDate and stopDate are of type datetime and startOvertime , stopOvertime are of type time(7) .

I want to create a new column with the date portion from stopDate and the time portion from startOvertime and copy that into a newly created column test-fill .

If I use formula (stopDate, startOvertime) then the value of the new datetime column is not right. Any proposals?

Answer 1

If you always want the new column with this information, then you can use a computed column:

alter table test add test-fill as
    (cast(cast(startDate as date) as datetime) + cast(overtime as datetime));

This doesn't actually add a new column. It just computes the values when you need them.

Answer 2

This should do it:

alter table [table-name] add [test-fill] datetime

update [table-name]
set [test-fill] = cast(startDate as date) + cast(stopOvertime as datetime)

First we add column to the table, then we update created cells with data.

Answer 3

ALTER TABLE TEST ADD NEWCOL DATETIME;
UPDATE TEST
SET NEWCOL = CAST((CAST(CAST(stopDate as date) as varchar(10))+' '+CAST(CAST(startOvertime as time) as varchar(10))) as DATETIME);