I need to add a new record to a database and one of the columns in my table is 'paymentDate', which is a "DateTime" field. Now the record I need to add is one in which the paymentDate is not known. I can't put in 'NULL' as SQL says 'Column 'paymentDate' cannot be null'. Also the '""' doesn't work in a datetime field.
If you have a paymentDate column and you don't know the date, then the column should allow NULL values. So, you should fix the data model:
alter table t alter column paymentDate datetime;
This will remove the not-NULL constraint, so you can add the data that you have.
I would be a little cautious, though. Why are you trying to add a row with an unknown payment date, if the designer of the table thought the value should never be NULL?
Related
I created a new column [LastLoginDate-NoTime] with the data type Date. I already have another column [LastLoginDate] that is of Datetime datatype.
Columns with the values
I am trying to copy values from the LastLoginDate column to the LastLoginDate-NoTime column using this query:
UPDATE [dbo].[SapUsersExt]
SET [LastLoginDate] = [LastLoginDate-NoTime]
But the problem I am having is that when I execute this query, it sets the data to null in the original column.
Screenshot: Error
I am also trying to convert the data from the LastLoginDate to just date format in the new column LastLoginDate-NoTime so that I can use it in my application. How would I do that?
I am trying to copy values from the LastLoginDate column to the LastLoginDate-NoTime column using this query
In that case, you're doing it exactly backwards - you should use this SQL instead:
UPDATE [dbo].[SapUsersExt]
SET [LastLoginDate-NoTime] = [LastLoginDate]
The first column - right after the SET - is the target column into which your values will be written.
The second column, after the = symbol, is where the data comes from (column or expression).
You had it backwards - setting the column with the actual values, to all NULL ....
This of course only works for a "one time" update - this will not keep your columns in sync over time, when new data is being inserted. For such a case, you'd need a computed column
ALTER TABLE dbo.SapUsersExt
ADD LastLoginDateOnly AS CAST(LastLoginDate AS DATE) PERSISTED;
or a trigger.
Or maybe, you don't even really need to actually store that date-only value - just use
SELECT
CAST(LastLoginDate AS DATE),
.......
if you need to date-only value from LastLoginDate
I am using Code first approach. how can i fix this problem?
I am assuming "Modified" column is a date time field in the table which is mandatory column.
You can resolve this issue in two ways
You can pass the "Modified" column field each time you do a insert.
Alter the column to accept null values if that field is not mandatory. Following is
sql query you can run to change the column to accept null values.
ALTER TABLE myTable ALTER COLUMN myColumn {DataType} NULL
I have the following table:
Study id
Pepsi 1
Coke 2
Sprite 3
I need to add a new column timestamp in the above table. i.e, study creation time and date will be stored in this column. What value should I have set for existing rows? Or should the "Timestamp" column have a value only for newly created rows?
I have used the following query to add the new column:
alter table Study add Timestamp datetime
There is no way to tell you what value you should set for existing rows - that is up to you to decide. If you can somehow retrieve the creation time by piecing together other information, then perhaps you can do this one by one, or you could just leave the existing rows to NULL.
Setting a default like GETDATE() for the column, and setting it to NOT NULL, forces all of the existing rows to inherit the current date and time - and you won't be able to set those back to NULL. I'm quite opposed to using garbage token values like 1900-01-01 to represent unknown, and I also don't believe in modifying the code to say something like "if the date is October 8, 2013 then that's because we just didn't know." So I would suggest adding a NULLable column with a default:
ALTER TABLE dbo.Study ADD CreationTime DATETIME NULL DEFAULT CURRENT_TIMESTAMP;
GO
Note that if you leave the column nullable, then the DEFAULT constraint is only useful if DML never sets it to NULL. If an INSERT statement, for example, explicitly places NULL there, the default is ignored. A way around this is to use a trigger (just like you would handle an update):
CREATE TRIGGER dbo.StudyCreationTime
ON dbo.Study
FOR INSERT
AS
BEGIN
SET NOCOUNT ON;
UPDATE s
SET s.CreationTime = CURRENT_TIMESTAMP
FROM dbo.Study AS s
INNER JOIN inserted AS i
ON s.StudyID = i.StudyID;
END
GO
what value should i have to set for previous studies
This would have to be defined by your business. This doesn't require a technical answer, so no one here can tell you what is right.
I have used below query to adding new column:
alter table Study add Timestamp datetime
This will work just fine, though this will allow nulls. I might suggest making this column non-null, adding a default, and changing the name of the column slightly since timestamp is a reserved word in SQL Server (a datatype that has not much to do with dates or times):
alter table Study add CreateDate datetime not null default current_timestamp;
Note that this will set all rows to the current date and time, so you may want to update them if you have more accurate data. Alternatively, simply create the column as nullable and existing rows won't get the default value, but rather null instead.
Another choice you might have to make is whether to use local time or UTC time (e.g. default getutcdate()). You might want to use the same time that your servers use or that other "CreateDate" columns use.
I have a temporary table in a PostgreSQL function and I want to insert a new VARCHAR column. It should have a value that depends on another column of the table, named "amount".
When the amount is positive I would like the value of the column row to be credit and when the value is negative the column should be debit.
I have one more request: I want to round the value of amount column in 2 decimal digits
You want ALTER TABLE ... ADD COLUMN followed by an UPDATE.
I initially said ALTER TABLE ... ADD COLUMN ... USING but that was wrong on two counts. ADD COLUMN takes a DEFAULT not USING - and You can't do it in one pass because neither a DEFAULT expression nor a USING expression may not refer to other columns.
So you must do:
ALTER TABLE tablename ADD COLUMN colname varchar;
UPDATE tablename SET colname = ( CASE WHEN othercol < 0 THEN 'Credit' ELSE 'Debit' END );
Think carefully about whether zero should be 'Debit' or 'Credit' and adjust the CASE accordingly.
For rounding, use round(amount,2). There isn't enough detail in your question for me to be sure how; probably by UPDATEing the temp table with UPDATE thetable SET amount = round(amount,2) but without the context it's hard to know if that's right. That statement irreversibly throws information away so it should only be used on a copy of the data.
I want to add or update columns using alter table if i am adding a new column i want show error. I am using the code below
alter table Personal_Details alter columns DOB datetime
if i uncheck the NULL to not NULL then it will shows column does not allow nulls; update fails;
i want to insert the fields in between columns not at end.
Plese fix my bug,
Thanks in advance.
The position of the column in the table declaration has nothing to do with its being NULL or NOT NULL.
If you are adding a column (of any type) which you want to be NOT NULL, i.e. you want to prohibit NULL values in that column, and the table already contains some rows, you must also provide some default value. For example:
ALTER TABLE Personal_Details
ADD COLUMN DOB datetime NOT NULL DEFAULT (GETDATE())
Otherwise the engine will attempt to add that column with NULLs as its values, which will violate the NOT NULL property, and the change, therefore, will be reverted.
Basically, the same applies when you want to set an existing column's NOT NULL property on while the column already contains NULLs. But in this case you must explicitly eliminate the NULLs before the change by either replacing them with values or removing the respective rows.
Source:
ALTER TABLE (Transact-SQL). (The particular section related to your problem is just above this code snippet.)
1)For ur adding column with not null problem
Use
ALTER TABLE Personal_Details ADD COLUMN DOB datetime NULL
Update the DOB column with the required dates and make sure there is no null in the column
then alter the column using
ALTER TABLE Personal_Details ALTER COLUMN DOB datetime not NULL
2)For your column going to the end problem...
you should not be worried...the order in which the columns are arranged doesnt matter...unless u are using a pathetic way of accessing data by column order..in which case again..u should stop accessing it by column order...
If the column order really matters you can change it using design option in the sql management table(rightclick on table >design and drag the column to its required place.)