Corrigir entradas duplicadas de banco de dados (bug do MySQL)

Para listar todas as anomalias:

SELECT name, count(*) FROM TableA GROUP BY name HAVING count(*) > 1;

Existem algumas maneiras de lidar com a exclusão de dups e seu caminho dependerá muito do número de dups que você possui.

Veja este SO questão de maneiras de removê-los da sua mesa.

Aqui está a solução que forneci lá:

-- Setup for example
create table people (fname varchar(10), lname varchar(10));

insert into people values ('Bob', 'Newhart');
insert into people values ('Bob', 'Newhart');
insert into people values ('Bill', 'Cosby');
insert into people values ('Jim', 'Gaffigan');
insert into people values ('Jim', 'Gaffigan');
insert into people values ('Adam', 'Sandler');

-- Show table with duplicates
select * from people;

-- Create table with one version of each duplicate record
create table dups as 
    select distinct fname, lname, count(*) 
    from people group by fname, lname 
    having count(*) > 1;

-- Delete all matching duplicate records
delete people from people inner join dups 
on people.fname = dups.fname AND 
   people.lname = dups.lname;

-- Insert single record of each dup back into table
insert into people select fname, lname from dups;

-- Show Fixed table
select * from people;