1SQL Basics: SELECT, WHERE, ORDER BY8 2Joins: INNER, LEFT, RIGHT, FULL, CROSS12 3Aggregation: GROUP BY, HAVING, COUNT, SUM10 4Subqueries & CTEs7 5Window Functions: ROW_NUMBER, RANK, LEAD, LAG8 6Indexing18 7Transactions & ACID4 8Normalization & Schema Design7 9SQL vs NoSQL2 10Connection Pooling6 11Query Optimization & EXPLAIN5 12Sharding & Partitioning7 13Database Internals: B-tree, MVCC, WAL1 14Stored Procedures, Views & Triggers6 15Migrations & Schema Changes1 16Practical SQL Queries34 17Advanced: Replication, Consistency, CAP5

17 topics141 Qs0%

Migrations & Schema Changes

Database & SQLTopic 15 of 171 question

Q1Zero-Downtime Schema Change on a Large Table: Expand-and-Contract

Expand (add nullable), dual-write, backfill in batches, switch reads and add constraints, then contract (drop old): never one blocking ALTER that rewrites and locks a huge table.