Question

I have a MySQL database table t with just two columns, id which is INT(11) and val which is VARCHAR(255). There are several millions of rows. How to quickly export the a whole column of id? Index is id and val, i.e. id is not unique in the column.

Is

SELECT DISTINCT id FROM t;

the best?

EDIT:

I’d like to save the result into a text file.

Answer 1

To export the unique ids into a file on the server you can use

SELECT DISTINCT id FROM t INTO OUTFILE 'all_the_unique_ids';

You will then find the file <mysql data dir>/<database name>/all_the_unique_ids on the server.

If you want to have the file on the client you need to use a MySQL client, e.g. MySQL’s own command line client:

mysql -e "SELECT DISTINCT id FROM t" > all_the_unique_ids