INSERT INTO table_a SELECT * FROM table_b;

CREATE TABLE table_new LIKE table_a;
INSERT INTO table_new SELECT * FROM table_b;
ALTER TABLE table_a RENAME table_old;
ALTER TABLE table_new RENAME table_a;
DROP TABLE table_old;

CREATE TABLE table_new LIKE table_a;
INSERT INTO table_new SELECT B.* FROM table_b B
LEFT JOIN table_a A USING (id) WHERE A.id IS NULL;
INSERT INTO table_a SELECT * FROM table_new;
DROP TABLE table_new;

mysqldum --tab=/path/to/serverlocaldir --single-transaction <database> table_a

create table table_b like table_a;

LOAD DATA INFILE '/path/to/serverlocaldir/table_a.txt'
  INTO TABLE table_b FIELDS TERMINATED BY 't' ...