I am trying to rename a column name in w3schools website
ALTER TABLE customers
RENAME COLUMN contactname to new_name;
However, the above code throws syntax error. What am I doing wrong?
You can try this to rename the column in SQL Server:-
sp_RENAME 'TableName.[OldColumnName]' , '[NewColumnName]', 'COLUMN'
sp_rename automatically renames the associated index whenever a
PRIMARY KEY or UNIQUE constraint is renamed. If a renamed index is
tied to a PRIMARY KEY constraint, the PRIMARY KEY constraint is also
automatically renamed by sp_rename. sp_rename can be used to rename
primary and secondary XML indexes.
For MYSQL try this:-
ALTER TABLE table_name CHANGE [COLUMN] old_col_name new_col_name
From "Learning PHP, MySQL & JavaScript" by Robin Nixon pg 185. I tried it and it worked.
ALTER TABLE tableName CHANGE oldColumnName newColumnName TYPE(#);
note that TYPE(#) is, for example, VARCHAR(20) or some other data type and must be included even if the data type is not being changed.
#Hannah's answer definitely helped me there but, as it took me some time to translate the syntax into real-life, I thought it might help someone to get an actual real-life example on how to use this syntax on MySQL.
1.So here again is the syntax:
ALTER TABLE tableName CHANGE oldColumnName newColumnName TYPE(#);
NB: TYPE(#) is, for example, VARCHAR(255) or some other data type and must be included even if the data type is not being changed.
2.Here is my real-life example, where "dashboard_dummy" is my table name, "product_code" my old column name and "order_id" my new column name:
ALTER TABLE dashboard_dummy CHANGE COLUMN product_code order_id int;
Hope it helps!
Related
I'm working on the project where one of my tables used Fox Pro in the past. They have used server side programming language (ColdFusion) to create unique ID for each record in the table. With SQL auto increment field I don't need this technique and I would like to set my key column to INT auto increment. I was wondering what is the best way to modify key column in my table? Here is example of my table design:
Column Name Data Type Allow Nulls
im_key char(10) No
I can't simply change the type to INT and set auto increment because my current type is char. If anyone can help please let me know. Thank you.
You can add a new column im_key_ident, set it as identity. Rename the old column: sp_rename 'table_name.im_key', 'im_key_old', 'COLUMN';. Finally, you can rename the new column: sp_rename 'table_name.im_key_ident', 'im_key', 'COLUMN';. You can choose to keep or to drop the old column.
If the im_key column is currently used as primary key, foreign key, in functions, procedures or in any other way, it will become very cumbersome, very fast...
I am working on SQL Server 2012:
I have a table with a primary key column as INT. I need to change this to a GUID.
Do I alter the table and remove int column as primary key?
Add the GUID column and set it as Primary and drop the old INT column?
Thank you.
You can't change primary key column,unless you drop it..Any operations to change its data type will lead to below error..
The object 'XXXX' is dependent on column 'XXXX'.
Only option is to
1.Drop primary key
2.change data type
3.recreate primary key
ALTER TABLE t1
DROP CONSTRAINT PK__t1__3213E83F88CF144D;
GO
alter table t1
alter column id varchar(10) not null
alter table t1 add primary key (id)
From 2012,there is a clause called (DROP_EXISTING = ON) which makes things simple ,by dropping the clustered index at final stage and also keeping old index available for all operations..But in your case,this clause won't work..
So i recommend
1.create new table with desired schema and indexes,with different name
2.insert data from old table to new table
3.finally at the time of switch ,insert data that got accumulated
4.Rename the table to old table name
This way you might have less downtime
You can change the date type of the primary key in three steps
Step 1 :- Drop the constraint associated with the Primary key
ALTER TABLE table_name
DROP CONSTRAINT constraint_name;
Step 2 :- Alter the Primay key column to a valid primary key data type
ALTER TABLE table_name
ALTER COLUMN pk_column_name target_data_type(size) not null;
Step 3 :- Make the altered column primary key again
ALTER TABLE table_name
ADD PRIMARY KEY (pk_column_name);
PS :-
You can get the Constraint name from the error message when you try to alter the
pk_column
If you already have data in the pk_column make sure the source and target data type of the column both can be used for the existing data. else another two steps would be needed to move the existing data to a temporary column and then perform the steps and bring back that data after vetting and dropping that temporary column.
Below is a script I wrote to help us deploy a change to primary key column data type.
This script assumes there aren't any non-primary key constraints (e.g. foreign keys) depending on this column.
It has a few safety checks as this was designed to be deployed to different servers (dev, uat, live) without creating side effects if the table was somehow different on a server.
I hope this helps someone. Please let me know if you find anything wrong before down-voting. I'm more than happy to update the script.
IF EXISTS(SELECT 1 FROM INFORMATION_SCHEMA.COLUMNS C WITH (NOLOCK) WHERE C.TABLE_CATALOG = '<<DB>>' AND C.TABLE_SCHEMA = 'dbo' AND C.TABLE_NAME = '<<Table>>'
AND C.COLUMN_NAME = '<<COLUMN>>' AND C.DATA_TYPE = 'int') -- <- Additional test to check the current datatype so this won't make unnecessary or wrong updates
BEGIN
DECLARE #pkName VARCHAR(200);
SELECT #pkName = pkRef.CONSTRAINT_NAME FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS pkRef WITH (NOLOCK)
WHERE pkRef.TABLE_CATALOG = '<<DB>>' AND pkRef.TABLE_SCHEMA = 'dbo' AND TABLE_NAME = '<<Table>>'
IF(#pkName IS NOT NULL)
BEGIN
-- Make sure the primary key name is the one you are going to use in script beyond this point.
IF(#pkName != '<<PRIMARY KEY NAME>>')
BEGIN
RAISERROR ('Unexpected primary key name - The primary key found has a different name than expected. Please update the script.', 16, 1);
RETURN;
END
ALTER TABLE dbo.<<Table>>
DROP CONSTRAINT <<PRIMARY KEY NAME>>; -- Note: this is not a string or a variable (just type the PK name)
SELECT 'Dropped existing primary key';
END
ALTER TABLE dbo.<<Table>> ALTER COLUMN ID BIGINT
SELECT 'Updated column type to big int';
ALTER TABLE dbo.<<Table>>
ADD CONSTRAINT <<PRIMARY KEY NAME>> PRIMARY KEY CLUSTERED (<<COLUMN>>);
SELECT 'Created the primary key';
END
ELSE
BEGIN
SELECT 'No change required.';
END
In case other tables reference your PK with indexed FK's, these are the steps you must follow.
In this example, the main table's called Main, the single referencing table Reference. I'm changing the datatype to NVARCHAR(7). To use it:
Find/replace all these table names with your own;
Modify the data type;
You might also need to separately find/replace the dbo schema;
I'm using syntax which includes constraint names - if you want, also update these to your preferred naming conventions.
ALTER TABLE dbo.Main ADD IdNew NVARCHAR(7);
UPDATE dbo.Main SET IdNew = Id;
-- For all tables with FK's to this Main:
ALTER TABLE dbo.Reference ADD MainIdNew NVARCHAR(7);
UPDATE dbo.Reference SET MainIdNew = MainId;
ALTER TABLE dbo.Reference DROP CONSTRAINT FK_Reference_MainId_Main_Id;
DROP INDEX IX_Reference_MainId ON dbo.Reference;
ALTER TABLE dbo.Reference DROP COLUMN MainId;
-- Until here
ALTER TABLE dbo.Main DROP CONSTRAINT PK_Main;
ALTER TABLE dbo.Main DROP COLUMN Id;
EXEC sp_rename 'dbo.Main.IdNew', 'Id', 'COLUMN';
ALTER TABLE dbo.Main ALTER COLUMN Id NVARCHAR(7) NOT NULL;
ALTER TABLE dbo.Main ADD CONSTRAINT PK_Main PRIMARY KEY (Id);
-- Again for all tables with FK's to this Main:
EXEC sp_rename 'dbo.Reference.MainIdNew', 'MainId', 'COLUMN';
ALTER TABLE dbo.Reference ADD CONSTRAINT FK_Reference_MainId_Main_Id FOREIGN KEY (MainId) REFERENCES dbo.Main(Id);
CREATE INDEX IX_Reference_MainId ON dbo.Reference(MainId);
Right in the table you want to change the PK type >> Modify. Go in the column, change the type and save. If you want to see the code for such a change, before saving, you can right-click >> "Generate Change Script ..".
Using Microsoft SQL Server Management Studio do the following:
Open table Design
Change the primary key column type or any other change which is also possible with this way
Right click on the design area and select Generate Change Script
Accept Validation Warning
Preview changes or save them in file.
Profit :)
This works for any change to the table, just bare in mind that SSMS creates a temporary second table to do the difficult changes like primary column type change.
This works for me in version 18.9 of the app.
When I try to change the data type of a column in a table by alter command...
alter table temp alter column id type bigserial;
I get
ERROR: type "bigserial" does not exist
How can I change the datatype from bigint to bigserial?
As explained in the documentation, SERIAL is not a datatype, but a shortcut for a collection of other commands.
So while you can't change it simply by altering the type, you can achieve the same effect by running these other commands yourself:
CREATE SEQUENCE temp_id_seq;
ALTER TABLE temp ALTER COLUMN id SET NOT NULL;
ALTER TABLE temp ALTER COLUMN id SET DEFAULT nextval('temp_id_seq');
ALTER SEQUENCE temp_id_seq OWNED BY temp.id;
Altering the owner will ensure that the sequence is removed if the table/column is dropped. It will also give you the expected behaviour in the pg_get_serial_sequence() function.
Sticking to the tablename_columnname_seq naming convention is necessary to convince some tools like pgAdmin to report this column type as BIGSERIAL. Note that psql and pg_dump will always show the underlying definition, even if the column was initially declared as a SERIAL type.
As of Postgres 10, you also have the option of using an SQL standard identity column, which handles all of this invisibly, and which you can easily add to an existing table:
ALTER TABLE temp ALTER COLUMN id
ADD GENERATED BY DEFAULT AS IDENTITY
ALTERing a column from BIGINTEGER to BIGSERIAL in order to make it auto-increment won't work. BIGSERIAL is not a true type, it is a trick that automates PK and SEQUENCE creation.
Instead you can create a sequence yourself, then assign it as the default for a column:
CREATE SEQUENCE "YOURSCHEMA"."SEQNAME";
ALTER TABLE "YOURSCHEMA"."TABLENAME"
ALTER COLUMN "COLUMNNAME" SET DEFAULT nextval('"YOURSCHEMA"."SEQNAME"'::regclass);
ALTER TABLE "YOURSCHEMA"."TABLENAME" ADD CONSTRAINT pk PRIMARY KEY ("COLUMNNAME");
This is a simple workaround:
ALTER TABLE table_name drop column column_name, add column column_name bigserial;
Sounds like alot of professionals out there on this subject... if the original table did indeed have data then the real answer to this dilemma is to have designed the db correctly in the first place. However, that being the case, to change the column rule (type) would require integrity verification of that column for the new paradigm. And, don't forget, anywhere where that column is manipulated (added/updated) then that would need to be looked into.
If it's a new table then okay, simples: delete column and re-add new column (takes care of the sequence for you). Again, design, design, design.
I think we've all fouled on this.
I have to add some NULL data into an otherwise not-nullable field. I checked :-
ALTER TABLE <table_name> DROP <default_constraint_name> ;
ALTER TABLE <table_name> ALTER COLUMN <column_name> <data_type> NULL;
ALTER TABLE <table_name> DROP COLUMN <column_name>;
but only the middle one seems fit for my usage because all I want o do is alter instead of . But it does not work. I am using Oracle 11g. Could you suggest anyother method or suggest what mistake I am doing in the 2nd ALTER TABLE SQL?
you can just disable constraint. And then enable it back when you want.
alter table
table_name
ENABLE constraint
constraint_name;
alter table
table_name
DISABLE constraint
constraint_name;
As stated in comment above, it may be a bad idea to allow NULLs in a column that previously did not allow them. Queries or code that already exist may rely on the assumption that the field cannot contain NULL, and could experience various problems if that assumption becomes false (errors if you're lucky, quietly producing incorrect or incomplete results if you're not).
That said, the syntax to simply remove the NOT NULL constraint permanently is:
ALTER TABLE table_name MODIFY column_name NULL;
You can also merely disable the constraint as indicated in another answer. To do this you need the constraint name which you can find by querying USER_CONSTRAINTS. This makes more sense if you expect to enable the constraint later.
I have a H2 database with 16 million entries and no primary key. I successfully added an auto-incrementing primary key using the following statements:
ALTER TABLE
PUBLIC.ADDRESSES ADD ID BIGINT AUTO_INCREMENT;
ALTER TABLE
PUBLIC.ADDRESSES ADD PRIMARY KEY (ID)
Now the problem is, that the column order is STREET, HOUSENUMBER, ..., ID, but I would like ID to be the first column of the table. It looks like there is a corresponding ALTER TABLE statement MySQL (see here), but I'm unable to adapt it to H2.
Long story short: How can I change the column order to ID, STREET, HOUSENUMBER ...? Is there a solution similar to:
ALTER TABLE "ADDRESSES" MODIFY COLUMN "ID" BEFORE "STREET";
Any help is kindly appreciated.
H2 does not currently support re-ordering columns. You would need to run multiple statements:
First, rename the column, then add a new column with the right name at the right position (alter table add supports positioning), and finally drop the old column.
Or, probably more elegant, use rename table and then create table ... as select.