I have a column details designed as varchar in oracle DB, this DB is being used now for customers and some rows already have data stored.
Now I want to change the column details to a Clob column. What is a smart way to accomplish this？
(as the previous answer) and here's the code:
ALTER TABLE atable
ADD (tmpdetails CLOB);
UPDATE atable SET tmpdetails=details;
COMMIT;
ALTER TABLE atable DROP COLUMN details;
ALTER TABLE atable
RENAME COLUMN tmpdetails TO details;
Add a clob column to the table
update clob column with values from varchar column
drop varchar column
rename clob column to varchar columns name
But this will not maintain the position of your column. It will move your column to the end of table. So if you want to maintain the position of your column as well follow these steps.
alter table atable add (tempdetails varchar2(4000));
update atable set tempdetails = details;
update atable set details = null; -- this is necessary to change data type
alter table atable modify details long; -- this is required because you can not change directly to clob.
alter table atable modify details clob;
update atable set details=tempdetails;
alter table atable drop column tempdetails;
This is the way in which you will maintain the data and position of your column intact even after changing the datatype. For detail information with example see here : http://www.oraclebin.com/2012/12/how-to-change-varchar2-to-clob-datatype.html
if you need your table data to be accessible during the process.. look at
DBMS_REDEFINITION
see a similar question on asktom
http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:1770086700346491686
Related
I am following the recommendation in this sql snowflake forum in order to transform an integer data column into a varchar by creating a new column. I want to drop the original integer column when I am done, but doing so always results in the new column no longer working and any future queries erroring out.
For instance, I have test_num is the integer and test_num_to_char is the varchar
alter table test_table
add test_num_to_char varchar as CAST(test_num as varchar)
then
alter table test_table
drop column test_num
select *
from test_table
results in an error message:
SQL execution internal error: Processing aborted due to error 300002:224117369
Is there a different transformation method that removes the dependency on the original integer column so I can drop it?
alter table test_table add test_num_to_char varchar(10);
go
update test_table set test_num_to_char = CAST(recno as varchar);
Try the TO_DECIMAL transformation method.
It's documentation is given here
I want to update and concatenate 3 columns in a new a attribute I've already created in my table. However when I execute my code, it puts attributes that before had values in null.
My code example:
update saber2012_1
set estu_fecha_nacimiento = Concat(estu_nacimiento_dia,'/',estu_nacimiento_mes,'/',estu_nacimiento_anno);
In this picture all values that is in null before these had values.
when I make this update
ALTER TABLE saber2012_uno ADD COLUMN punt_c_naturales int;
update saber2012_uno set punt_c_naturales = round((PUNT_BIOLOGIA::numeric + PUNT_FISICA::numeric + PUNT_QUIMICA::numeric) / 3,0);
alter table saber2012_uno DROP COLUMN PUNT_BIOLOGIA;
alter table saber2012_uno DROP COLUMN PUNT_FISICA;
alter table saber2012_uno DROP COLUMN PUNT_QUIMICA;
all is well. but I do not know because previous update is incorrect.
Perhaps you want concat_ws():
update saber2012_1
set estu_fecha_nacimiento = concat_ws('/', estu_nacimiento_dia, estu_nacimiento_mes, estu_nacimiento_anno);
This will ignore any of the arguments that are NULL.
However, your update will not change any other columns in the table. Perhaps the results are just coming back in a different order, when you query after the update.
I've managed to create the following column in a new table:
CREATE TABLE t_issue_dates as
SELECT issue_d,
cast(substr(issue_d,5,4) as numeric) as issue_year
FROM myDB
(The code recodes a year-month variable to a year-only variable)
However, i can't add this variable to my existing table "myDB". I've tried using the:
ALTER TABLE myDB ADD v_year - command, but i can't manage to get it right.
Does anyone have an idea how i add the above variable to the "original" table myDB?
Thank you!
First, many databases support computed or generated columns. That means that you can add a virtual column to the database by doing:
alter table t_issue_dates add issue_year as (cast(substr(issue_d, 5, 4) as numeric));
I recommend this approach because issue_year is always up-to-date.
Second, you can do this as an actual column, but the value can get out-of-date and needs to be re-calculated for each inserted/updated row:
alter table t_issue_dates add issue_year numeric;
update t_issue_dates
set issue_year = cast(substr(issue_d, 5, 4) as numeric);
For the record, I would use int rather than numeric.
Assuming you are using MSSQL. It would be worth of reading documentation or a simple google on how to insert
Adding column :
Alter table t_issue_dates
Add V_year Int
Next step: This will only insert data for this particular column.
Insert into t_issue_dates (v_year)
SELECT
cast(substr(issue_d,5,4) as numeric)
FROM myDB
I need to alter my table and change a VARCHAR2 column to be CLOB.
The following script is too slow (8 minutes) for me when having 1 million records:
ALTER TABLE SA.EVENT_PARAMS ADD COLUMN NEW_VALUE CLOB(65344);
UPDATE SA.EVENT_PARAMS SET NEW_VALUE=VALUE;
ALTER TABLE SA.EVENT_PARAMS DROP COLUMN VALUE;
RENAME COLUMN SA.EVENT_PARAMS.NEW_VALUE TO VALUE;
Is there another way to do this? Talking about apache derby.
Thanks
I am trying to alter a datatype for a derby db column. The current price column is set as DECIMAL(5,0). I would like to alter it to DECIMAL(7,2). I did this :
alter table item alter column price set data type DECIMAL(7,2);
But it did not work, and showing the error:
Error: Only columns of type VARCHAR may have their length altered.
May I know how is it possible to alter it? Thank you.
Here is the Derby SQL script to change column MY_TABLE.MY_COLUMN from BLOB(255) to BLOB(2147483647):
ALTER TABLE MY_TABLE ADD COLUMN NEW_COLUMN BLOB(2147483647);
UPDATE MY_TABLE SET NEW_COLUMN=MY_COLUMN;
ALTER TABLE MY_TABLE DROP COLUMN MY_COLUMN;
RENAME COLUMN MY_TABLE.NEW_COLUMN TO MY_COLUMN;
I think you can do like this:
ALTER TABLE SCHEMA.TABLE ALTER "COLUMN-NAME" SET DATA TYPE VARCHAR(255);
(column-Name SET DATA TYPE VARCHAR(integer)) for Datatype String as an example...
Here's a slightly more complicated way to alter the column's data type in this fashion:
Add a new column, of the desired data type
Issue "update ... set new-column = old-column to copy the data from the old column to the new column
drop the old column
Rename the new column to have the name of the old column.
Slightly more steps, but in the end the effect will be the same.
If you have trouble working out the exact details of the SQL to do this, let us know and we'll help.
You can alter table like this:
ALTER TABLE [table] ALTER COLUMN [column] SET DATA TYPE [type];
Or in Rails, just use:
change_column :table_name, :column_name, :integer
Posgtes Solution :
ALTER TABLE prices_table ALTER price_column TYPE decimal (7,2 )