I would like to rename a column in DB2 on the iSeries platform. The link below is related, however, I do not have a primary key or constraint defined on the columns I would like to rename. In addition, I'm not certain that they are on the iSeries as well.
Rename column in DB2
However, I decided to give it a go with the following statement:
ALTER TABLE MYLIB.MYFILE RENAME COLUMN COL0001 TO COL0002;
Post execution, I am given the following warning:
Additionally, I do not see a RENAME COLUMN in the docs:
https://www.ibm.com/support/knowledgecenter/en/ssw_ibm_i_71/db2/rbafzatabl.htm
Is this something that is not possible on V7R1 DB2?
There is no RENAME COLUMN clause in the ALTER TABLE statement in DB2 for IBM i.
You may probably achieve the same with the following:
ALTER TABLE MYLIB.MYFILE ADD COLUMN COL0002 ...;
UPDATE MYLIB.MYFILE SET COL0002 = COL0001;
ALTER TABLE MYLIB.MYFILE DROP COLUMN COL0001;
Related
Let's say I have a table Student with just 2 columns - id bigint, name varchar(50).
I'm trying to rename it and add column in a same single query in PostgreSQL version 11.16 like below:
ALTER TABLE student
RENAME COLUMN name TO fullname,
ADD COLUMN roll_no varchar(30);
But I got this error:
Syntax error at or near "ADD"
Is it possible? If not, why?
Actually, that is not possible. I got this from the StackOverflow answer. One RENAME is possible for only one statement. Even multiple RENAME commands are also not possible. Here is the postgres manual.
I am trying to modify a column data type and name in one command.
Is it possible to apply multiple alter statements on one column in one code line? Is that the correct syntax?
ALTER TABLE tb_table
ALTER COLUMN colum_date
SET DATA TYPE TIMESTAMP NOT NULL
RENAME COLUMN colum_date TO colum_timestamp;
I have been looking for related bibliography but could not find much information on the web.
According to the documentation renaming a column is an action that cannot be combined with others but requires its own statement. So no, you cannot do what you want in one statement.
But you can do it in one transaction. Setting the datatype and setting the NOT NULL constraint requires two actions though. But both of that actions can be in one statement.
BEGIN TRANSACTION;
ALTER TABLE tb_table
ALTER COLUMN colum_date
SET DATA TYPE TIMESTAMP,
ALTER COLUMN colum_date
SET NOT NULL;
ALTER TABLE tb_table
RENAME COLUMN colum_date
TO colum_timestamp;
COMMIT TRANSACTION;
It's been a while.
Using DB2 10 for z/OS, I've been asked to change a specific column in a table from decimal(7,2) to decimal(7,4). Sounds easy, right?
alter table MySchema.MyTable
alter column myColumn
set data type decimal(7,4);
But, DB2 responds with this error: "Attributes specified for column 'MYCOLUMN' are incompatible with existing column definition."
I had thought that converting from decimal(7,2) to decimal(7,4) would be pretty straightforward, but DB2 disagrees.
Outside of dropping the table and recreating it from scratch, what alternatives do I have?
Thanks in advance!
Dave
The reason Db2 doesn't like that change is you're going from from 99999.99 to 999.9999
Is that really what you want? Going from (7,2) to (9,4) would just add two more decimal places without losing any data and should be allowed by the Db.
Db2 for i gives a warning, but allows you to ignore the warning...
Create a new column ALTER ADD COLUMN of the right type, use an UPDATE to populate it, ALTER DROP COLUMN the old column. RENAME COLUMN so set the name of the original column.
I have a column where I want to change the data type. I currently am using Redshift. I know I can use the alter table statement to change the datatype, but this would change the order of the columns.
Is there a way to change the datatype without changing the order of the column?
I would recommend creating a new table with the schema you want and copying it over from the old table using a insert into new_table (select * from old_table) statement (here you can also do any casting to the new data type), after which you can drop the old table and rename the new one:
drop table old_table;
alter table new_table rename to old_table;
Using ALTER TABLE table_name ALTER COLUMN column_name TYPE new_data_type will not change the order of the columns in your table.
Please note that this clause can only changes the size of a column defined as a VARCHAR data type.
There are also other limitations described in AWS documentation of ALTER TABLE
I am working with hive version 0.9 and I need delete columns of a hive table. I have searched in several manuals of hive commands but I only I have found commands to version 0.14. Is possible to delete a column of a hive table in hive version 0.9? What is the command?
Thanks.
We can’t simply drop a table column from a hive table using the below statement like sql.
ALTER TABLE tbl_name drop column column_name ---- it will not work.
So there is a shortcut to drop columns from a hive table.
Let’s say we have a hive table.
From this table I want to drop the column Dob. You can use the ALTER TABLE REPLACE statement to drop a column.
ALTER TABLE test_tbl REPLACE COLUMNS(ID STRING,NAME STRING,AGE STRING); you have to give the column names which you want to keep in the table
There isn't a drop column or delete column in Hive.
A SELECT statement can take regex-based column specification in Hive releases prior to 0.13.0, or in 0.13.0 and later releases if the configuration property hive.support.quoted.identifiers is set to none.
That being said you could create a new table or view using the following:
drop table if exists database.table_name;
create table if not exists database.table_name as
select `(column_to_remove_1|...|column_to_remove_N)?+.+`
from database.some_table
where
...
;
This will create a table that has all the columns from some_table except the columns named column_to_remove_1, ... , to column_to_remove_N. You can also choose to create a view instead.
ALTER TABLE table_name REPLACE COLUMNS ( c1 int, c2 String);
NOTE: eliminate column from column list. It will keep matched columns and removed unmentioned columns from table schema.
we can not delete column from hive table . But droping a table(if its external) in hive and the recreating table(with column excluded) ,wont delete ur data .
so what can u do is(if u dont have table structure) run this command :
show create table database_name.table_name;
Then you can copy it and edit it (with column eliminated).Afterwards you can do as per invoke the shell
table details are empid,name,dept,salary ,address. i want remove address column. Just write REPLACE COLUMNS like below query
jdbc:hive2://> alter table employee replace columns(empid int, name string,dept string,salary int);
As mentioned before, you can't drop table using an alter statement.
Alter - replace is not guaranteed to work in all the cases.
I found the best answer for this here:
https://stackoverflow.com/a/48921280/4385453