LOAD DATA INFILE easily convert YYYYMMDD to YYYY-MM-DD?
This loads and converts in one step, no need for another table. For more information see the manual.
LOAD DATA INFILE 'file.txt'
INTO TABLE t1
FIELDS TERMINATED BY ','
(column1, @var1, column3, ...)
SET column2 = STR_TO_DATE(@var1,'%Y%m%d')