Dependent Origination

unique constraints in mysql

Posted on: December 4, 2012

1. how to show the current constraints of a table?

mysql> show create table table_name;

It will also show updates, not just what is being executed at the time of create table.

2. drop a unique constraint

mysql> alter table table_name drop index constraint_name;

even if you didn’t give the constraint a name when you created it, you can still find the name from the above ‘show create table’ command.

3. add a new unique constraint

mysql> alter table table_name add constraint constraint_name unique (column 1, column 2, …);

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