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;
Related
I'm trying to change all the USER-DEFINED columns to TEXT in a specific view using pgsql.
Is it possible to do that in a single alter table query ou do I need to check first what columns contain that dataype and then perform the dataype change one by one?
This is what I'm trying:
ALTER TABLE if exists "schemaName"."Table_A"
ALTER COLUMN (
select column_name
from information_schema.columns inf
where table_name = 'Table_A' and inf.data_type = 'USER-DEFINED')
TYPE TEXT;
I'm getting and error in the subquery start "("
You need to do this one by one. Generally speaking such DDL statements cannot work on several objects in one statement.
For ALTER TABLE, see: https://www.postgresql.org/docs/12/sql-altertable.html.
FOR ALTER VIEW, see: https://www.postgresql.org/docs/current/sql-alterview.html
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;
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 was simply wondering if there was a performance or other technical reason for you to be unable to perform a ALTER TABLE ALTER COLUMN statement with multiple columns within the same line e.g.
ALTER TABLE tblGeneric ALTER COLUMN Generic1 VARCHAR(255), Generic2 VARCHAR(255);
This is exclusively a restriction of t-sql as you can in fact comma separate columns with the MODIFY statement of mysql.
I just thought it odd, especially considering the MODIFY of mysql, that you can do a same line multi ALTER TABLE ADD statement but not a same line multi ALTER. I was just wondered if there is any particular documented reason for this or at least if it's in a issues list.
SQL Server T-SQL doesn't allow multiple columns to be changed in one ALTER TABLE command (unlike some other languages where it's possible).
Please follow this MSDN link for ALTER command syntax and explanation.
However, you can do multiple ADD or multiple DROP COLUMN, but just one ALTER COLUMN.
Assume I have a table named tracker with columns (issue_id,ingest_date,verb,priority)
I would like to add 50 columns to this table.
Columns being (string_ch_01,string_ch_02,.....,string_ch_50) of datatype varchar.
Is there any better way to add columns with single procedure rather than executing the following alter command 50 times?
ALTER TABLE tracker ADD COLUMN string_ch_01 varchar(1020);
Yes, a better way is to issue a single ALTER TABLE with all the columns at once:
ALTER TABLE tracker
ADD COLUMN string_ch_01 varchar(1020),
ADD COLUMN string_ch_02 varchar(1020),
...
ADD COLUMN string_ch_50 varchar(1020)
;
It's especially better when there are DEFAULT non-null clauses for the new columns, since each of them would rewrite the entire table, as opposed to rewriting it only once if they're grouped in a single ALTER TABLE.