MySQL - How to increase varchar size of an existing column in a database without breaking existing data?

I have a column that is currently varchar(100) and I want to make it 10000.

is it as simple as

alter table table_name set column col_name varchar (10000);

I am afraid to corrupt the exiting data. Will I be ok if I run this query? Or should I do I alter the column another way?

Thanks!

It's safe to increase the size of your varchar column. You won't corrupt your data.

If it helps your peace of mind, keep in mind, you can always run a database backup before altering your data structures.

By the way, correct syntax is:

ALTER TABLE table_name MODIFY col_name VARCHAR(10000)

Also, if the column previously allowed/did not allow nulls, you should add the appropriate syntax to the end of the alter table statement, after the column type.

I normally use this statement:

ALTER TABLE `table_name`
  CHANGE COLUMN `col_name` `col_name` VARCHAR(10000);

But, I think SET will work too, never have tried it. :)

I'd like explain the different alter table syntaxes - See the MySQL documentation

For adding/removing defaults on a column:

ALTER TABLE table_name
ALTER COLUMN col_name {SET DEFAULT literal | DROP DEFAULT}

For renaming a column, changing it's data type and optionally changing the column order:

ALTER TABLE table_name
CHANGE [COLUMN] old_col_name new_col_name column_definition
[FIRST|AFTER col_name]

For changing a column's data type and optionally changing the column order:

ALTER TABLE table_name
MODIFY [COLUMN] col_name column_definition
[FIRST | AFTER col_name]

For me worked this one:

ALTER TABLE tablename MODIFY fieldname VARCHAR(128) NOT NULL;

I am using mysql and below syntax worked well for me,

ALTER TABLE table_name MODIFY col_name VARCHAR(12);

For me this has worked-

ALTER TABLE table_name ALTER COLUMN column_name VARCHAR(50)

use this syntax: alter table table_name modify column col_name varchar (10000);