SQL Server layers run from the network protocols down to SQLOS and the data and log files. Here is what each layer does, and how physical architecture differs from logical architecture.
OR in a JOIN: Preserve Matching Pairs When Rewriting
OR in a JOIN matches either key while returning each pair once. Compare NULL cases and pair counts before rewriting. Measure the actual plan only after proving the results.
Finding the Right System View for the Question You Have
Choose SQL Server system views by the question they answer, distinguish catalog metadata from runtime counters, and understand reset boundaries.
AND and OR: Parentheses Make Predicate Precedence Clear
AND and OR predicates need explicit grouping. Use a complete small truth table to expose which alternatives share a common requirement.
SQLite or SQL Server Express for a Small App
SQLite or SQL Server Express depends on write concurrency, deployment, backup, and the growth path your small application really needs.
Multiset Intersection: Keep the Matching Duplicate Occurrences
Multiset intersection keeps the duplicate count shared by both inputs rather than returning each common value once. I pair numbered occurrences to express that requirement. The result should contain the smaller count for each equivalent value.
Binary Conversion Styles: Hex With and Without 0x
Binary conversion styles control hexadecimal prefixes. Pair the output and input styles, preserve empty bytes and verify a complete round trip.