MySQL - Make an existing Field Unique

Question

I have an already existing table with a field that should be unique but is not  I only know this because an entry was made into the table that had the same value as another  already existing  entry and this caused problems    How do I make this field only accept unique values

User · Answer

Just write this query in your db phpmyadmin   ALTER TABLE TableName ADD UNIQUE  FieldName    Eg  ALTER TABLE user ADD UNIQUE  email

User · Answer

ALTER IGNORE TABLE mytbl ADD UNIQUE  columnName       For MySQL 5 7 4 or later   ALTER TABLE mytbl ADD UNIQUE  columnName        As of MySQL 5 7 4  the IGNORE clause for ALTER TABLE is removed and   its use produces an error    So  make sure to remove duplicate entries first as IGNORE keyword is no longer supported   Reference

User · Answer

The easiest and fastest way would be with phpmyadmin structure table     There it s in Russian language but in English Version  should be the same  Just click Unique button  Also from there you can make your columns PRIMARY or DELETE

User · Answer

If you also want to name the constraint  use this   ALTER TABLE myTable   ADD CONSTRAINT constraintName      UNIQUE  columnName

User · Answer

This code is to solve our problem to set unique key for existing table   alter ignore table ioni groups add unique  group name

User · Answer

CREATE UNIQUE INDEX foo ON table name  field name   You have to remove duplicate values on that column before executes that sql  Any existing duplicate value on that column will lead you to mysql error 1062

User · Answer

ALTER IGNORE TABLE mytbl ADD UNIQUE  columnName     is the right answer   the insert part   INSERT IGNORE INTO mytable

[mysql] MySQL - Make an existing Field Unique

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