How to Drop a Unique Constraint from Table Column

How to drop a unique constraint from table column?

SKINDER, your code does not use column name. Correct script is:

declare @table_name nvarchar(256)  
declare @col_name nvarchar(256)  
declare @Command  nvarchar(1000)  

set @table_name = N'users'
set @col_name = N'login'

select @Command = 'ALTER TABLE ' + @table_name + ' drop constraint ' + d.name
    from sys.tables t 
    join sys.indexes d on d.object_id = t.object_id  and d.type=2 and d.is_unique=1
    join sys.index_columns ic on d.index_id=ic.index_id and ic.object_id=t.object_id
    join sys.columns c on ic.column_id = c.column_id  and c.object_id=t.object_id
    where t.name = @table_name and c.name=@col_name

print @Command

--execute (@Command)

How to drop a unique constraint on a column in Postgres?

To find the name of the unique constraint, run

SELECT conname
FROM pg_constraint
WHERE conrelid = 'cart'::regclass
  AND contype = 'u';

Then drop the constraint as follows:

ALTER TABLE cart DROP CONSTRAINT cart_shop_user_id_key;

Replace cart_shop_user_id_key with whatever you got from the first query.

Is it possible to drop a unique constraint from a column?

Flask-Migrate, or rather Alembic, will not autodetect anonymous constraints. But you can create a manual Alembic migration file to drop the constraint.

Create an empty migration file:

flask db revision -m 'Drop unique constraint'

Edit the file to drop the constraint:

def upgrade():
    op.drop_constraint("name_of_constraint", "table_name")

def downgrade():
    op.create_index(...)

I suggest you copy the create_index from the migration file that created the constraint in the first place, if possible.

Then you can upgrade your database normally:

flask db upgrade

Dropping Unique constraint from MySQL table

A unique constraint is also an index.

First use SHOW INDEX FROM tbl_name to find out the name of the index. The name of the index is stored in the column called key_name in the results of that query.

Then you can use DROP INDEX:

DROP INDEX index_name ON tbl_name

or the ALTER TABLE syntax:

ALTER TABLE tbl_name DROP INDEX index_name

Remove Unique constraint on a column in sqlite database

SQLite only supports limited ALTER TABLE, so you can't remove the constaint using ALTER TABLE. What you can do to "drop" the column is to rename the table, create a new table with the same schema except for the UNIQUE constraint, and then insert all data into the new table. This procedure is documented in the Making Other Kinds Of Table Schema Changes section of ALTER TABLE documentation.

How to drop unique constraint from mysql table on a foreign key column

So, your problem is you are trying to drop a index which is used in Foreign Key Constraint. So you can not do it directly. Follow below steps:

1. Drop the constraint requests_ibfk_1 which is your foreign key.

alter table requests drop foreign key requests_ibfk_1

2. Then Drop the UNIQUE KEY on column work_id.

alter table requests drop index work_id

3. Again Add Foreign Key on Column work_id.

alter table requests add CONSTRAINT `requests_ibfk_1` FOREIGN KEY (`work_id`) REFERENCES `work` (`work_id`)

DEMO

How to remove unique key from mysql table

All keys are named, you should use something like this -

ALTER TABLE tbl_quiz_attempt_master
  DROP INDEX index_name;

To drop primary key use this one -

ALTER TABLE tbl_quiz_attempt_master
  DROP INDEX `PRIMARY`;

ALTER TABLE Syntax.

Unable to drop UNIQUE constraint

Your Query will return the Index name you will need to Drop the index created for the Unique Constraint

use this query

DROP INDEX Index_Name
ON Schema.Table_Name

A unique Constraint creates a Unique Non-Clustered Index behind the scenes to enforce the uniqueness on that column.

Also if you need to create this INDEX again after insert you can simply disable it and once you have done whatever you wanted to do, you can enable it afterwards.

something like this...

ALTER INDEX [Index_Name] ON Schema.Table_Name DISABLE
GO

/* Do your Stuff here  */

ALTER INDEX [Index_Name] ON Schema.Table_Name REBUILD
GO

---

Related Topics