CREATE TABLE temp_table (id int(11), generated_id varchar(40));

LOAD DATA INFILE '/tmp/generated_ids.csv'
INTO TABLE temp_table
FIELDS TERMINATED BY ',' 
ENCLOSED BY '"' 
LINES TERMINATED BY '\n'
(id, generated_id);

UPDATE customer INNER JOIN temp_table ON temp_table.id = customer.id
SET customer.generated_id = temp_table.generated_id;

DROP TABLE temp_table;