How do I delete all the duplicate records in a MySQL table without temp tables

Question

I\'ve seen a number of variations on this but nothing quite matches what I\'m trying to accomplish.

I have a table, TableA, which contain the answers gi

Answer 1

Add Unique Index on your table:

ALTER IGNORE TABLE `TableA`   
ADD UNIQUE INDEX (`member_id`, `quiz_num`, `question_num`, `answer_num`);

Another way to do this would be:

Add primary key in your table then you can easily remove duplicates from your table using the following query:

DELETE FROM member  
WHERE id IN (SELECT * 
             FROM (SELECT id FROM member 
                   GROUP BY member_id, quiz_num, question_num, answer_num HAVING (COUNT(*) > 1)
                  ) AS A
            );

Answer 2

An alternative way would be to create a new temporary table with same structure.

CREATE TABLE temp_table AS SELECT * FROM original_table LIMIT 0

Then create the primary key in the table.

ALTER TABLE temp_table ADD PRIMARY KEY (primary-key-field)

Finally copy all records from the original table while ignoring the duplicate records.

INSERT IGNORE INTO temp_table AS SELECT * FROM original_table

Now you can delete the original table and rename the new table.

DROP TABLE original_table
RENAME TABLE temp_table TO original_table

Answer 3

Instead of drop table TableA, you could delete all registers (delete from TableA;) and then populate original table with registers coming from TableA_Verify (insert into TAbleA select * from TAbleA_Verify). In this way you won't lost all references to original table (indexes,... )

CREATE TABLE TableA_Verify AS SELECT DISTINCT * FROM TableA;

DELETE FROM TableA;

INSERT INTO TableA SELECT * FROM TAbleA_Verify;

DROP TABLE TableA_Verify;