INSERT INTO without duplicates

I want to do this

INSERT INTO AdminAccounts (Name) 
SELECT Name
FROM Matrix

But I don't want to create duplicates. ie, I ran this a few weeks ago and need to update the data.

This will insert new Name fields that were not previously in the Matrix table.

INSERT IGNORE
INTO AdminAccounts (Name) 
SELECT Name
FROM Matrix;

If you do not trust INSERT IGNORE, there is an alternative where you can manifest the new Name values before inserting them:

CREATE TABLE NewName SELECT Name FROM Matrix WHERE 1=2;
INSERT INTO NewName
    SELECT Name FROM AdminAccounts A
    LEFT JOIN Matrix B USING (Name)
    WHERE B.Name IS NULL;
INSERT INTO Matrix (Name) SELECT Name FROM NewNames;

The table NewName collects only those tables in AdminAccounts that are not in Matrix at present. This can give you a chance to look over the new Names. Afterwards, you can INSERT everything in NewName into Matrix.

StackExchange Database Administrators Q#9689, answer score: 7