varchar vs text - MySQL

Question

in my project an user can write comment [plain text], and view others comment, can delete own comment, but can not update comment !
In this case which would should i use

Answer 1

(You have multiple questions; I will address the one that is in the title.)

The only difference between VARCHAR(4000) and TEXT is that an INSERT will truncate to either 4000 characters or 65536 bytes, respectively.

For smaller values than 4000, there are cases where the temp table in a complex SELECT will run faster with, for example, VARCHAR(255) than TINYTEXT. For that reason, I feel that one should never use TINYTEXT.

Answer 2

it depends on the application behavior. space allocated inside block's table decrease space for other columns and decrease density data inside it. if full table scan is used by mysql, many blocks are scanned, it's inefficient. so it depends on your sql requests.

Answer 3

Varchar is usually faster in retrieval when the size is reasonable, as it is stored within the table, where as TEXT is stored off the table with a pointer to location.

Thanks

Answer 4

To protect yourself from XSS attack, encode it using the htmlentities function.

Other than that, the choice of datatype has most to do with how big the content will be. If it may exceed 4048 characters, then use a text datatype. If many posts will be large, using a text datatype may reduce wasted data space and may perform slightly better than a giant varchar, but it depends upon your situation, you would be best to test the alternatives.

I generally prefer varchar because it's easier to deal with from a coding perspective, if nothing else, and fall back to text if the contents may exceed the size of a varchar.