database - Will adding large columns (VARCAHR) to MySQL table have significant impact on performance? -

database - Will adding large columns (VARCAHR) to MySQL table have significant impact on performance? -

i sorry if question newbish, have little knowledge of databases.

i working on web based application manage organization users. number of records 10,000-20,000. wanted add together column table allow staff add together notes users record, in case. assume not utilized often.

will adding varchar column table have important performance impact on db? suggest separating notes table, relational users table?

adding big varchar() column can have impact on performance, not necessarily. key thought here storing info on pages in database. reading table requires reading pages contain records. normally, many records fit on single page. if record quite large, few records fit on page. can impact performance because more pages need read (for queries) or records don't fit memory.

in case, there mitigating circumstances:

you can have field , never populate it. hence, record sizes never large. all queries "needle-in-the-haystack" queries, using index fetch 1 or few records. if store column text, separately allocated object. if have "few" users, total info size little (say measured in few megabytes), performance isn't issue.

there methods mitigate performance, such putting longer columns in separate table.

so, impact on performance depends on overall size of database, structure, , how used.

mysql database web-applications