Changing datatype ...

[capricorn732]

I get a dumped mysql database from a client. It contains abt 23 - 27 tablesand each table contain records around 70,000.
The problem is I need to get data from three diffrent tables. In 1st table Id is Integer, primary and auto, in 2nd table its Integer and in 3rd table its varchar(10) but data in this field is numeric (1, 2, 3, ...). The only solution comes to my mind is change Id's datatype in 3rd table to Integer.
My question ... will changing datatype of Id in 3rd table, effect on (numeric) data in this field ??
As this data base contains many record so I want to be sure.

[Anon]

As long as you only have integers in the varchar(10) field, you should be OK.

Now, that said, I always take precautions and make a copy of the table and change the datatype on it. I have performed this in two different ways: copying the table, then altering the datatype, or creating a brand-new table from a SQL script that converts the datatype for me. Whatever works for you.