I have an existing DB2 database and a table named
employee with columns
id,e_name,e_mobile_no,e_dob,e_address.
How can I add a new column e_father_name before e_mobile_no?
You should try using the ADMIN_MOVE_TABLE procedure which allows to change the table structure.
The ALTER TABLE only allows adding columns to the end of the table. The reason is that it would change the physical structure of the table, i.e., each row would need to be adapted to the new format. This would be quite expensive.
Using the mentioned procedure ADMIN_MOVE_TABLE you would copy the entire table and during that process change the table structure. It requires a significant amount of space and time.
In DB2 IBM i v7r1 you can do it, try on your DB2 version
alter table yourtable
add column e_father_name varchar(10) before e_mobile_no
I always do the following --
Take a backup/dump of table data and db2look
(If you dump to a CSV file as I do I suggest dumping in the new format so for example put null for the new column in the right place.
Drop table and indexes
Create table with the new colunn
Load data with old values
Recreate all indexes and runstats.
Once you have done it a few times it becomes old hat.
Related
I created a empty table , I m unable to alter the Datatype of the field from web ui, is there any command line or Alter table command for Altering the datatype from INTEGER -> STRING
You need to recreate the schema, you cannot alter types.
If you want to copy the old data. Please make sure you create a temporary table, then once the schema is ready, you can query the old table and write to the new table making the transformation.
I want to create a new table with one of the columns linked/updated by a table on another database (but on the same server).
so when table A column is updated it will automatically update table b's column with the same information no data will be entered into this column from table b.
I have tried various different ways but can't find a way to do this with out updating column manually or setting up a server agent any help would be great.
if you want to make cross server query, please check sp_addlinkedserver
https://msdn.microsoft.com/en-us/library/ms190479.aspx
Once it is linked, just create a trigger, where you can use
select * from [server].[database].[schema].[table]
Is it possible to rename a table in Firebird or I should create a new table and then move the data using insert?
Apparently not.
You must either create a new table, copying over old values or create a view with the intended name which is identical to the original table.
See http://www.firebirdfaq.org/faq363/ for further details.
It is possible to change the column name by:
ALTER TABLE "tableName" ALTER "columnName" TO "NewColumnName";
sometimes i face the following case in my database design,, i wanna to know what is the best practice to handle this case:::
for example i have a specific table and after a while ,, when the database in operation and some real data are already entered.. i need to add some required fields (that supposed not to accept null)..
what is the best practice in this situation..
make the field accept null as (some data already entered in the table ,, and scarify the important constraint )and try to force the user to enter this field through some validation in the code..
truncate all the entered data and reentered them again (tedious work)..
any other suggestions about this issue...
It depends on requirements. If the data to populate existing rows for the new column isn't available immediately then I would generally prefer to create a new table and just populate new rows when the data exists. If and when you have all the data for every row then put the new column into the original table.
If possible i would set a default value for the new column.
e.g. For Varchar
alter table table_name
add column_name varchar(10) not null
constraint column_name_default default ('Test')
After you have updated you could then drop the default
alter table table_name
drop constraint column_name_default
A lot will come down to your requirements.
It depends on your application, your database scheme, your entities.
The best way to go about it is to truncate the data and re - enter it again, but it need not be too tedious an item. Temporary tables and table variables could assist a great deal with this issue. A simple procedure comes to mind to go about it:
In SQL Server Management Studio, Right - click on the table you wish to modify and select Script Table As > CREATE To > New Query Editor Window.
Add a # in front of the table name in the CREATE statement.
Move all records into the temporary table, using something to the effect of:
INSERT INTO #temp SELECT * FROM original
Then run the script to keep all your records into the temporary table.
Truncate your original table, and make any changes necessary.
Right - click on the table and select Script Table As > INSERT To > Clipboard, paste it into your query editor window and modify it to read records from the temporary table, using INSERT .. SELECT.
That's it. Admittedly not quite straightforward, but a well - kept database is almost always worth a slight hassle.
Is it possible to copy a table (with definition, constraints, identity) to a new table?
Generate a CREATE script based on the table
Modify the script to create a different table name
Perform an INSERT from selecting everything from the source table
No, not really, you have to script it out, then change the names
you can do this
select * into NewTable
FROM OldTable
WHERE 1 =2 --if you only want the table without data
but it won't copy any constraints
It's not the most elegant solution, but you could use a tool like the free Database Publishing Wizard from Microsoft.
It creates an SQL script of the table definition including data and including indexes and stuff. But you would have to alter the script manually to change the table name...
Another possibility:
I just found this old answer on SO.
This script is an example to script the constraints of all tables, but you can easily change it to select only the constraints of "your" table.
So, you could do the following:
Create the new table with data like SQLMenace said (select * into NewTable from OldTable)
Add constraints, indexes and stuff by changing this SQL script