Question

Hey I have an SQL Table which has a column for storing date but the date column has a type varchar. I want to change the type to date but I don’t want the actual data to be lost in that column. How can I achieve that.

Manually taking a backup of the table and then entering each entry? or there is some other cool way to do it ? Actually the data is huge

Thanks

Answer 1

My way of doing this:

(1) Add a new column:

ALTER TABLE yourtable 
ADD COLUMN `new_date` DATE NULL AFTER `views`; 

(2) Update the new column

UPDATE yourtable SET new_date = old_date;

Take care of the datas formatting in old_date. If it isn’t formatted yyyy-mm-dd, you might have to STR_TO_DATE or some string-replacements in this UPDATE-statement here to fit your purposes.

Example:

If your data looks like this: mmmm dd, yyyy, hh:mm (p.e. May 17, 2012, 8:36 pm) , you can update like this:

UPDATE yourtable
SET new_date = STR_TO_DATE(old_date, "%M %e, %Y");

STR_TO_DATE basically reverse engineers string data to a date value.

(3) Delete the old column

ALTER TABLE yourtable 
DROP COLUMN `old_date`; 

(4) Rename the new column

ALTER TABLE yourtable 
CHANGE `new_date` `old_date` DATE NULL; 

Done!