Dropping Unique constraint from MySQL table

Question

How can I drop the "Unique Key Constraint" on a column of a MySQL table using phpMyAdmin?

Answer 1

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

Answer 2

You can DROP a unique constraint from a table using phpMyAdmin as requested as shown in the table below. A unique constraint has been placed on the Wingspan field. The name of the constraint is the same as the field name, in this instance.

Answer 3

The indexes capable of placing a unique key constraint on a table are PRIMARY and UNIQUE indexes.

To remove the unique key constraint on a column but keep the index, you could remove and recreate the index with type INDEX.

Note that it is a good idea for all tables to have an index marked PRIMARY.

Answer 4

To add UNIQUE constraint using phpmyadmin, go to the structure of that table and find below and click that,

To remove the UNIQUE constraint, same way, go to the structure and scroll down till Indexes Tab and find below and click drop,

Hope this works.

Enjoy ;)

Answer 5

If you want to remove unique constraints from MySQL database table, use alter table with drop index.

Example:

CREATE TABLE unique_constraints (
    unid INT,
    activity_name VARCHAR(100),
    CONSTRAINT activty_uqniue UNIQUE (activity_name),
    PRIMARY KEY (unid)
);

ALTER TABLE unique_constraints
DROP INDEX activty_uqniue;

Where activty_uqniue is UNIQUE constraint for activity_name column.

Answer 6

For WAMP 3.0 : Click Structure Below Add 1 Column you will see '- Indexes' Click -Indexes and drop whichever index you want.

Answer 7

The constraint could be removed with syntax:

ALTER TABLE

As of MySQL 8.0.19, ALTER TABLE permits more general (and SQL standard) syntax for dropping and altering existing constraints of any type, where the constraint type is determined from the constraint name: ALTER TABLE tbl_name DROP CONSTRAINT symbol;

Example:

CREATE TABLE tab(id INT, CONSTRAINT unq_tab_id UNIQUE(id));

-- checking constraint name if autogenerated
SELECT * FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE TABLE_NAME = 'tab';

-- dropping constraint
ALTER TABLE tab DROP CONSTRAINT unq_tab_id;

db<>fiddle demo

Answer 8

This might help:

Inside your sql terminal

FIRST STEP:

SHOW INDEX FROM {YOUR_TABLE_NAME}

SECOND STEP:

SHOW INDEX FROM {YOUR_TABLE_NAME} WHERE Column_name='ACTUAL_COLUMN_NAME_YOU_GOT_FROM_FIRST_STEP_OUTPUT'

THIRD STEP:

ORIGINAL_KEY_NAME_VALUE = SECOND_STEP_RESPONSE["Key_name"]

FOURTH STEP:

ALTER TABLE {YOUR_TABLE_NAME} DROP INDEX ${ORIGINAL_KEY_NAME_VALUE}

Answer 9

while dropping unique key we use index

ALTER TABLE tbl
DROP INDEX  unique_address;

Answer 10

my table name is buyers which has a unique constraint column emp_id now iam going to drop the emp_id

step 1: exec sp_helpindex buyers, see the image file

step 2: copy the index address

step3: alter table buyers drop constraint [UQ__buyers__1299A860D9793F2E] alter table buyers drop column emp_id

note:

Blockquote

instead of buyers change it to your table name :)

Blockquote

thats all column name emp_id with constraints is dropped!