Default value for a text column

I have a column in my table having data type as TEXT.

How can I give it a default NULL value, so that when there is not entry in the column it doesn't consume memory.

I was reading a similar que开发者_C百科stion on a forum where they said column should be allowed for null values; I did that but it doesn't work..

TEXT does not support default values of anything but NULL. As such, it's implicitly DEFAULT NULL, so you should not need to change anything.