normalization
pessimistic/optimistic locking
trees
lists and queues
upsert/replace/affected rows
images (mod_rewrite, sep. tbl)
surrogate keys
case statement
lookup table / enum
sequences vs. (multi-)autoincrement + replication
groupwise
group_concat(), with rollup
sort by random
csv import
pivot tables
xml, serialized strings ..
full text search
ranking
emulate check constr. (view)
affected rows
partitioning
pagenation