Short exercises on one technology
SQL · Querying
Read a schema you did not write and get the rows out of it: filters, joins, subqueries, sets and aggregates, with the NULLs and orphans that bite.
SQL · Designing and writing
Turn requirements into tables, constraints and keys, then insert, load, update and delete without leaving the data in a state you did not mean.
SQL · Viewing
Read and judge views: aggregated, layered, partitioned, and the ones that hand a role exactly what it may see and nothing more.
SQL · Optimizing
Read a query plan and say why it is slow; add the index that changes it, and see what two concurrent sessions do to a balance.
SQL · Scaling and security
Read roles, injections, prepared statements, a replica that lags and a shard that runs hot, and say which one your system has.
C# · Reading Other People's Code
Read C# somebody else wrote, run it, and explain why it prints what it prints: struct copies, closures, deferred queries, disposal and equality.
Rep progress is tracked separately from projects.