Update all columns

I'm rather new to MySQL. But I know some stuff. I need some help though.. Basically, I have a database, for example
DB: site
Table: category
Column: 1,value,3

So as you can see I tagged the value in bold. What I need help with is, how do I update the columns, so I can replace all the value in it with a new one, yes, I want to update/replace all the current data with the one I want to.

I'm sorry for my English, not my first language. And sorry if I didn't explain it very well, if you need help to, please post here, I'll try to explain more specifically.

 

update category set value = 'value' where id = '1'

 

Yeah I know that. But the thing is, I want to update the value for all of them. For example, I have a 3 category's, let's name them:
a
b
c

in a I got "hi" , in b I got "sup" , in c I got "dude". So what I want to do is, I want to replace hi,sup,dude with for example "123". You know what I mean?

 

huh? you want to update each record with the same text string?

 

Yeah. It's not exactly a category thing. Just giving some examples.

 

just remove the where id = '1' sentence
update category set fieldName = 'value'

 

Thank you so much crivion!!!