I have a column datedocumented in the format YYYYMMDD and of the datatype nvarchar. I want to change the data type to datetime and update the column name exdatedocumented and alter the table using ALTER .can anyone help in this.I have tried something like this
update dbo.table2
set [DateDocumented] = convert(datetime,CAST([DateDocumented] as datetime),130)
I ended up getting error
Msg 242, Level 16, State 3, Line 1
The conversion of a nvarchar data type to a datetime data type resulted in an out-of-range value.
The statement has been terminated
.
You should be able to just change the column type:
alter dbo.table2 alter column DateDocumented datetime;
Your column is in a format suitable for conversion. If you wanted to use default formats instead, just do:
update table dbo.table2
set [DateDocumented] = convert(datetime, CAST([DateDocumented] as datetime));
This should also allow the column to be converted to a datetime.
1st change that column name then alter table
sp_RENAME 'dbo.table2.datedocumented', 'exdatedocumented' , 'COLUMN'
go
ALTER TABLE dbo.table2
ALTER COLUMN exdatedocumented datetime;
It seems we have two things going on here. Changing the type for a column. And changing the name for a column. Let's try to keep these separate so not to confuse things. I will adress the changing of type (from varchar to datetime):
First of all: Why datetime? Why note datetime2 (with whatever fractions of seconds you want, for instance datetime2(0))? The new types for date and time has been around for 10 years now!
Anyhow, you apparently have values in your table which are not valid dates! First thing you need to do is to find those rows and handle them. Lets say that you will change to datetime2(0), if not, then just change below to datetime instead:
SELECT *
FROM dbo.Table2
WHERE TRY_CAST(DateDocumented AS datetime2(0)) IS NULL
Related
I am trying to change a column's datatype. The column of type VARCHAR has thousands of GUID values like look those shown below:
b1f4ff32-48d4-494e-a32c-044014cea9
bc5a1158-b310-49ff-a1f3-09d4f8707f69
4b7ebc9d-9fa1-42d9-811e-0b7b4b7297a
fc7ba848-98ea-4bc6-add7-11f0ee9c6917a21
485741ff-2ab2-4705-91b3-136389948b7c
I need to convert the column type to unqiqueidentifier using the script below. Can I do that safely without corrupting the column data?
alter table MyTable
alter column guidColumn uniqueidentifier not null
If you change the data type SQL Server will first check if all the values in the columns can be implicitly converted to the new data type; if they cannot then the ALTER will fail. If they can, then they will be implicitly converted and the ALTER will be successful (assuming no dependencies of course).
For a uniqueidentifier then either it's a valid value or it's not, so either the data will all convert or the ALTER won't take place. For something like a date and time data type, however, you could very easily end up with incorrect data if the data is stored in an ambiguous format like dd/MM/yyyy. This could mean a value like '12/05/2022' ends up being stored as the date value 2022-12-05 rather than 2022-05-12. For such scenarios you would therefore want to UPDATE the data to an unambiguous format first, and then ALTER the data type of the column.
The uniqueidentifier type is considered a character type for the purposes of conversion from a character expression, and therefore is subject to the truncation rules for converting to a character type.
Also there are limitations, uniqueidentifier type is limited to 36 char
So if you decide to truncate the table like in this example:
DECLARE #ID NVARCHAR(max) = N'0E984725-C51C-4BF4-9960-E1C80E27ABA0wrong';
SELECT #ID, CONVERT(uniqueidentifier, #ID) AS TruncatedValue;
This will be the result:
String
Truncated Value
0E984725-C51C-4BF4-9960-E1C80E27ABA0wrong
0E984725-C51C-4BF4-9960-E1C80E27ABA0
So, if your string is more or less than 36 it will not truncate correctly.
For more information check Microsoft documentation:
https://learn.microsoft.com/en-us/sql/t-sql/data-types/uniqueidentifier-transact-sql?view=sql-server-ver15
The date format in the table is YYYYMMDD and I would like to convert it to the following format but it is failing with an error:
2019-07-23 00:00:00.000
Conversion failed when converting date and/or time from character string
Here is the statement I'm using:
convert(varchar(10), convert(datetime, InstallDate0), 23)
The real problem is the choice of your datatype. varchar is the wrong choice. As a result, it seems that you now have some rows where the value of the "date" has been lost, as it can't be converted to a date.
To properly fix this problem, fix your datatype. Firstly I would create a new column to store the bad values:
ALTER TABLE YourTable ADD BadDate varchar(20); --as it's yyyyMMdd you don't need more than 8 characters, but we'll assume you have some really bad values
UPDATE YourTable
SET BadDate = InstallDate0
WHERE TRY_CONVERT(datetime,InstallDate0) IS NULL;
Now that you've done that, time to update the existing column:
UPDATE YourTable
SET InstallDate0 = CONVERT(varchar(8),TRY_CONVERT(datetime, InstallDate),112);
This'll set every value to the yyyyMMdd format where the value can be converted. NOw you can alter your table:
ALTER TABLE YourTable ALTER COLUMN InstallDate0 date; --AS it's yyyyMMdd, it seems silly to actually use datetime
Now you have a proper datetime column.
You'll then need to inspect the values of BadDate and try to correct them (or admit that any information they held has been lost for ever).
If you "must" have another column with the format, then add a further column:
ALTER TABLE YourTable ADD InstallDate0_f AS CONVERT(varchar(23),InstallDate0,121);
You can determine where the problems are using TRY_CONVERT(). The problem would seem to be the conversion to a datetime, so try this:
select InstallDate0
from t
where try_convert(datetime, InstallDate0) is null;
I have a question related to the conversion of varchar to datetime.
This topic was covered already in the thread
SQL Server Convert Varchar to Datetime
but I would like to advance it bit further.
I have performed BULK INSERT into predefined tables where VARCHAR(255)
is the destination. I have a table dbo.USR_02_ALL_RAW and the field GLTGB which
holds strings in the following format: 07/16/2016.
I can convert it as a single string by the following code:
DECLARE #Date varchar(255)
set #Date= '07/16/2016'
SELECT CONVERT(datetime,RIGHT(#Date,4)+LEFT(#Date,2)+SUBSTRING(#Date,4,2))
and it gives me a result:
2016-07-16 00:00:00.000
However I would like to pass to the code the whole field GLTGB from the table
dbo.USR_02_ALL_RAW, convert it from VARCHAR into DATETIME and update the field GLTGB with these results.(converting the whole field from varchar to datetime)
Thank you!
First clear this, you want to Bulk insert or Bulk update. Since you already have a column GLTGB. If you want to update the value only.
update tab set GLTGB =
CONVERT(datetime,RIGHT(GLTGB,4)+LEFT(GLTGB,2)+SUBSTRING(GLTGB,4,2))
Or
If you want to update the field from varchar to datetime. Then process is little bit lengthy.
Alter table tab add newcol datetime --- Add new datetime type column
update tab set newcol =
CONVERT(datetime,RIGHT(GLTGB,4)+LEFT(GLTGB,2)+SUBSTRING(GLTGB,4,2)) --- update value in new column
Alter table tab drop column GLTGB --- drop GLGTB column
Alter table tab add GLGTB datetime --- add GLGTB column as datetime type
update tab set GLGTB = newcol --- update value from GLGTB from newcol
Alter table tab drop column newcol ---- remove unnecessary newcol
If you convert a value to datetime, then update the same database column it came from with the value then, since that column is still varchar, SQL will have to convert the value back to varchar again in order to store it. So you can't achieve anything useful with that kind of simple approach.
f you want to actually change the data type of the column, and also convert all the values, then I think you need to go through the following process:
1) Create a new varchar column in your table (which will be temporary)
2) copy all the data values from the GLTGB column into the new column (using an UPDATE statement)
3) Drop the GLTGB column
4) Re-create it with the same name but with datetime type
5) Use an UPDATE statement to re-populate the new GLTGB column from your temporary column
6) Finally, drop the temporary column
There may be a simpler way but that seems like the obvious process.
You can use the following code for updating but before that, you need to change the data type of your field to DateTime
update dbo.USR_02_ALL_RAW
set GLTGB=cast(CONVERT(datetime,RIGHT(#Date,4)+LEFT(#Date,2)+SUBSTRING(#Date,4,2)) as datetime)
ALTER TABLE table_name
ALTER COLUMN columnWithDate datetime;
columnWithDate is a type of nvarchar(255), data are in 2018.06.19. form. I've checked all distinct values and there are one row with NULL value in columnWithDate.
I get the following error runninf the alter command:
The conversion of a nvarchar data type to a datetime data type resulted in an out-of-range value.
What am I missing here?
You need to first change your values to a unambiguous format and then change the datatype. For the value you have that would be simply removing the ., as that produces the ISO format yyyyMMdd:
UPDATE YourTable
SET YourDateColumn = REPLACE(YourDateColumn,'.','');
ALTER TABLE YourTable ALTER COLUMN YourDateColumn datetime; --Should this not be a date?
As I comment though, date would likely be a better choice here, as you have no time portion in your value(s).
I suspect the extra dot(.) after the date is the culprit. In your example 2018.06.19.
This below snippet giving me the same error
DECLARE #DATE NVARCHAR(255)= N'2018.06.19.'
SELECT CAST(#DATE AS datetime)
Msg 242, Level 16, State 3, Line 3 The conversion of a nvarchar data
type to a datetime data type resulted in an out-of-range value.
So just remove the dot from the nvarchar field befor Alter.
The value is not correct somewhere in the column. I would suggest finding it:
select columnWithDate
from table_name
where try_convert(datetime, columnWithDate) is null and
columnWithDate is not null;
If you want to remove incorrect dates, then update first:
update table_name
set columnWithDate = try_convert(datetime, columnWithDate);
This converts the value back to a string, but the string should be convertible on your system right back to a datetime.
I have a datetime column that I need to alter to be a varchar column.
Using the statement below, the strings produced have this format: "Jan 18 2010 5:28PM"
ALTER TABLE Thinger
ALTER COLUMN LastUpdateDate varchar(16) NOT NULL
I would like strings produced to have a yyyyMMdd format (giving 20100118) instead. Is there a way to do this?
Thanks
Bad, Bad idea...never ever store dates in varchar columns, now you will get garbage in there in different formats
Also why varchar(16) when you want yyyyMMdd?
if you want the output to be in a different format do it in the presentation layer or use convert
SELECT CONVERT(CHAR(8),GETDATE(),112)
now if you really want to do what you say you want to do
run your script and then do
UPDATE Table
SET LastUpdateDate = CONVERT(CHAR(8),(CONVERT(DATETIME,CONVERT(varchar,LastUpdateDate))),112)
But again..bad bad bad idea
Also the next version of SQL Server will make formatting a lot easier see: Format function in SQL Server Denali CTP3
Try this script:
ALTER TABLE Thinger ADD LastUpdateDateText VARCHAR(16) NOT NULL
GO
UPDATE Thinger SET LastUpdateDateText = CONVERT(VARCHAR(8), LastUpdateDate, 112)
GO
ALTER TABLE Thinger DROP COLUMN LastUpdateDate
GO
sp_RENAME 'Thinger.LastUpdateDateText' , 'LastUpdateDate', 'COLUMN'
GO