How do I modify a MySQL column to allow NULL?

Question

MySQL 5.0.45

What is the syntax to alter a table to allow a column to be null, alternately what's wrong with this:

ALTER mytable MODIFY mycolumn varchar(255) null;

I interpreted the manual as just run the above and it would recreate the column, this time allowing null. The server is telling me I have syntactical errors. I just don't see them.

Answer 1

You want the following:

ALTER TABLE mytable MODIFY mycolumn VARCHAR(255);

Columns are nullable by default. As long as the column is not declared UNIQUE or NOT NULL, there shouldn't be any problems.

Answer 2

Your syntax error is caused by a missing "table" in the query

ALTER TABLE mytable MODIFY mycolumn varchar(255) null;

Answer 3

Under some circumstances (if you get "ERROR 1064 (42000): You have an error in your SQL syntax;...") you need to do

ALTER TABLE mytable MODIFY mytable.mycolumn varchar(255);