I'm setting up to gather long time statistics. It will be recorded in little blocks that I'm planning to stick all into one TEXT field, latest first.. sorta like this
The answer to your two questions is "yes":
update t set field = concat($newval, field) where id = $id;
select left(field, 100) from t where id = $id;
(These assume that you have multiple rows in the table.)
That said, you method of storing the data is absolutely not the right thing to do in a relational database.
Presumably, you want a table that looks something like this:
create table t ( tId int auto_increment primary key, creationDate date, data <something> );
(This may be more complicated if
data should be multiple columns.)
Then you insert into the table:
insert into t(createDate, data) select $date, $data;
And you can fetch the most recent row:
select t.* from t order by tId desc limit 1;
All of these are just examples, because your question doesn't give a complete picture of the data.