请用三个要点回答下述问题，每个要点最多20个字，并且每个要点用"*" 号开头。用*0 varchar = ...*开头，以*keyword table schema*结尾，整体不超过3行。
user
*0 varchar = The database column type for variable-length strings*
*1 All types of characters can be stored*
*2 Define the maximum byte length*
*keyword table schema*
assistant