I have an existing table in SQL that includes an ID column. I need to have another Textcolumn in same table in a way it is always equal to ID value but stored as text. For now I am updating Textcolumn daily but I want it to be auto filled.
Is that possible?
I actually just recommend that you select your ID column as text if you have that requirement:
SELECT ID, CAST(ID AS varchar(55)) ID_text
FROM yourTable;
If you need to work this ID column as text, then cast as do whatever you need, e.g. a string concatenation.
There are many ways to do the job.
From now on during insert it into the column by casting it as varchar.
You can use trigger for updating the column. For more information creating trigger are in the following link
you can use computed column for solve your problem automatically
CREATE TABLE [dbo].[test](
[Id] [int] NULL,
[Idtext] AS (cast ([id] as nvarchar(10)))
) ON [PRIMARY]
this is my sample table
in my sample table the IdText Column fill automatics when you insert a record in your table
if you wants to add column on the existing table you can use this command
ALTER TABLE [Table Name] ADD [Column Name] AS (cast([id] as nvarchar(10)))
You can use a Trigger to update it automatically.
Related
I have a table viz. expenses with three columns as under
ExpenseId int NOT NULL,
ExpenseName varchar(50) NOT NULL,
Invalid bit NOT NULL
To add a new column (OldCode char(4) not null), I used design feature for tables in Microsoft SQL Server Management Studio. But I get following error
'Expenses' table
- Unable to modify table. Cannot insert the value NULL into column 'OldCode', table 'TransportSystemMaster.dbo.Tmp_Expenses'; column does not allow nulls. INSERT fails. The statement has been terminated.
Incidentally I have been able to add same column with same specifications to other tables of the same database.
Any help?
Your Table Consist of Existing Records
and you are pushing a new column of type NOT NULL.
so for older records the data have to be something.
try something like this
ALTER TABLE MY_TABLE ADD Column_name INT NULL
GO
UPDATE MY_TABLE <set valid not null values for your column>
GO
ALTER TABLE MY_TABLE ALTER COLUMN Column_name INT NOT NULL
GO
Since OldCode is NOT NULL, you should specify a default value for it.
when you have some rows on your table you can't add a column that is not nullable you should provide a default value for it
Alter Table table_name add OldCode int not null DEFAULT(0);
You have to specify values for all the 4 fields of the table, its purely because, while designing the table you set the definition of the columns to be not null. Again you are adding a new column called OldCode and setting to be not null, all ready existing records hasn't got a value. So that is the reason its complains
I need to add a constraint to one table in my database. The table name is Experience. And there is a column named ToDate. Every time the select statement executes like following.
select ToDate from Experience
It should return current date.
So every time select statement executes, the ToDate column get updated with current date.
I know I can do this with some type of sql trigger but is there a way to do it by sql constraint.
like
alter table add constraint...
Any help will be appreciated.
Thanks
You can use a computed column. That's specified like colname as <expression>:
create table t1(id int, dt as getdate());
insert t1 values (1);
select * from t1;
To add contraint ...
create table tbl (id int identity, dt datetime, colval varchar(10))
ALTER TABLE dbo.tbl
ADD CONSTRAINT col_dt_def
DEFAULT GETDATE() FOR dt;
Example of inserting to the table ..
insert into dbo.tbl(colval)
select 'somevalue'
select * from dbo.tbl
The result will be ..
id dt colval
1 2014-08-19 13:31:57.577 somevalue
You cannot use a constraint, because a constraint is basically a rule on what can go in the table, how the table can relate to others, etc. It has no bearing on the data in the table once it goes into the table. Now if I am understanding you correctly, you want to update the ToDate column whenever you select that column. Now you can't use a trigger either as mentioned here and here. They suggest a stored procedure where you would use an update followed by an insert. This is probably my preferred SQL method to go with if you have to use it repeated, which you seem to have to do. Though Andomar's answer is probably better.
Try this link code make help full
http://www.sqlatoms.com/queries/how-to-use-the-getdate-function-in-sql-server-3/
CREATE TABLE ProductOrders
(
OrderId int NOT NULL PRIMARY KEY IDENTITY,
ProductName nvarchar(50) NOT NULL,
OrderDate datetime NOT NULL DEFAULT GETDATE()
)
I have created a table with column id as varchar2(20). Now I want to modify it and change size to 13 i.e column id varchar2(13). How to achieve it? Thanks in advance
p.s.: I don`t have any data in my table.
You may try this for Oracle:-
alter table tablename modify
(
column_name varchar2(13)
);
Also If you dont have any data in the table then you can also drop the table and then create the table with the columname as varchar2(13)
Just run this query for MySQL:
ALTER TABLE tablename CHANGE column `id` varchar2(13);
See here for more details. If you have additional constraints on this column, specify those as well.
I am stumped,
I am trying to alter the increment value of Identity columns in a collection of existing MS SQL tables (which all have data) and have been trying to research if it is possible to do without writing custom scripts per table.
I can't find a solution that doesn't require dropping and recreating the tables which would require a different script for each table as they each have different column lists.
for example i want to change the existing table
CREATE TABLE [dbo].[ActionType](
[ID] [int] IDENTITY(1,1) NOT NULL,
[Action] [varchar](100) NOT NULL,
CONSTRAINT [PK_ActionType] PRIMARY KEY CLUSTERED
(
[ID] ASC
) ON [PRIMARY]
) ON [PRIMARY]
To
CREATE TABLE [dbo].[ActionType](
[ID] [int] IDENTITY(1,5) NOT NULL,
[Action] [varchar](100) NOT NULL,
CONSTRAINT [PK_ActionType] PRIMARY KEY CLUSTERED
(
[ID] ASC
) ON [PRIMARY]
) ON [PRIMARY]
Via something like
exec sp_AlterIncrement #TABLE_NAME = 'ActionType', #NEW_ICREMENT = 5
While keeping the data.
This would fix a big deployment issue i am facing right now so any help would be appreciated
You can not alter identity increment after you create it.It is possible just to change seed value with DBCC Chekident .
You should drop and recreate the column.
I had to do that before on a small table and it's fairly easy to do, trick is that you have to update it to something that currently doesn't exist as a key, and then back, since you can't increment it by 1 because that key already exists. It takes 2 updates, for a table with IDs smaller than 100 for example:
update my_table set id = id+100;
update my_table set id = id-99;
But anyways , I do not understand why you want to alter the identity value, Because anyhow you will keep the same as primary key or part of the clustered key.
Also, if any change in the column type is being required then i don't think that there is a possibility without altering the table structure.
Alter table ActionType
Alter column ID
You can also revert to the original structure when not required. This can be used for the specified case as well, As if you require this on demand basis.
Please suggest so that i can provide the further feedback.
Couple of things, maybe too much info but helpful when do stuff like this. The following will set the increment to whatever you want:
DBCC CHECKIDENT ([DB.Schema.Table], reseed, 0) --First record will have a 1. You can set it to any value
If you want to insert data into a table that has an identity but you need to force the value to something specific, do this:
SET IDENTITY_INSERT [DB].[schema].[Table] ON
...Add your data here
SET IDENTITY_INSERT [DB].[schema].[Table] OFF
Sometimes this is necessary.this might provide an answer. For example existing table is identity(1,1) [ex below would be A]
It contains value but you would like to change it to increment of to let's say so that it works well with another table [ex below would be B]
So a would have odd ids + whatever it use to contains.while be would now have even number
this script show you how to do it.
create table A(id int identity(1,1),v char)
insert into A
Select 'A'
union select 'B'
union select 'C'
go
create table B(id int identity(1,2),v char)
go
SET IDENTITY_INSERT B ON
GO
insert into B(Id,v)
Select Id,v from A
go
SET IDENTITY_INSERT B OFF
GO
insert into B
Select 'D'
union select 'E'
go
drop table A
go
EXEC sp_RENAME 'B' , 'A'
go
Select * from A
go
Select max(Id)+1 from A
go
create table B(id int identity(8,2),v char)
go
insert into B
Select 'A'
union select 'B'
union select 'C'
go
Select * from B
If you need to reenumerate or compress your Identity field, the easiest way is as follows:
Convert, temporarily, your identity filed into an integer
Replace the values using for example an Excel sheet in other to fill them up
Copy and Paste the column in your Excel file into the Int field.
Save the table
Open it again in design mode and change back the Int field into an Identity
If this Identity field is used in a child table, make sure you have a trigger to also export the new values into the dependant tables .
And that's all.
If you need to control Identity data in your applicaton, just change it to Int and manage the incremental values with code with the Dmax function.
Hope it helps
Can I add a column which is I specify as NOT NULL,I don't want to specify the DEFAULT value but MS-SQL 2005 says:
ALTER TABLE only allows columns to be added that can contain nulls, or have a DEFAULT definition specified, or the column being added is an identity or timestamp column, or alternatively if none of the previous conditions are satisfied the table must be empty to allow addition of this column. Column 'test' cannot be added to non-empty table 'shiplist' because it does not satisfy these conditions.
If YES, please let me know the syntax, if No please specify the reason.
No, you can't.
Because if you could, SQL wouldn't know what to put as value in the already existing records. If you didn't have any records in the table it would work without issues.
The simplest way to do this is create the column with a default and then remove the default.
ALTER TABLE dbo.MyTable ADD
MyColumn text NOT NULL CONSTRAINT DF_MyTable_MyColumn DEFAULT 'defaultValue'
ALTER TABLE dbo.MyTable
DROP CONSTRAINT DF_MyTable_MyColumn
Another alternative would be to add the column without the constraint, fill the values for all cells and add the constraint.
Add the column to the table, update the existing rows so none of them are null, and then add a "not null" constraint.
No - SQL Server quite reasonably rejects this, because it wouldn't know what value existing rows should have
It's easy to create a DEFAULT at the same time, and then immediately drop it.
I use this approach to insert NOT NULL column without default value
ALTER TABLE [Table] ADD [Column] INT NULL
GO
UPDATE [Table] SET [Column] = <default_value>
ALTER TABLE [Table] ALTER COLUMN [Column] INT NOT NULL
No.
Just use empty string '' (in case of character type) or 0 (if numeric), etc as DEFAULT value
No you cannot. But you can consider to specify the default value to ('')
No, you can't, as SQL Server, or any other database engines will force this new column to be null for existing rows into your data table. But since you do not allow a NULL, you are required to provide a default value in order to respect your own constraint. This falls under great sense! The DBE will not extrapolate a value for non-null values for the existing rows.
#Damien_The_Unbeliever's comment ,
Is it adding computed column? Neither question nor answer implied anything like that. In case of computed column the error states:
"Only UNIQUE or PRIMARY KEY constraints can be created on computed columns, while CHECK, FOREIGN KEY, and NOT NULL constraints require that computed columns be persisted"
OK, if to continue this guessing game, here is my script illustrating the adding of "NOT NULL" column in one "ALTER TABLE" step:
CREATE TABLE TestInsertComputedColumn
(
FirstName VARCHAR(100),
LastName CHAR(50)
);
insert into TestInsertComputedColumn(FirstName,LastName)
select 'v', 'gv8';
select * from TestInsertComputedColumn;
ALTER TABLE TestInsertComputedColumn
ADD FullName As FirstName + LastName PERSISTED NOT NULL;
select * from TestInsertComputedColumn;
--drop TABLE TestInsertComputedColumn;
I used below approach it worked for me
Syntax:
ALTER TABLE <YourTable> ADD <NewColumn> <NewColumnType> NOT NULL DEFAULT <DefaultValue>
Example:
ALTER TABLE Tablename ADD ColumnName datetime NOT NULL DEFAULT GETDATE();
As an option you can initially create Null-able column, then update your table column with valid not null values and finally ALTER column to set NOT NULL constraint:
ALTER TABLE MY_TABLE ADD STAGE INT NULL
GO
UPDATE MY_TABLE SET <a valid not null values for your column>
GO
ALTER TABLE MY_TABLE ALTER COLUMN STAGE INT NOT NULL
GO