How SQL Strings Are Parsed Into Structured Commands in a Custom Database

A developer building a custom transactional key-value store from scratch has reached the query layer, where raw SQL strings must be translated into structured operations. The storage engine natively understands keys, values, and SSTables but has no concept of SQL, so a dedicated parsing layer is required. The parser converts statements like CREATE TABLE, INSERT, and SELECT into structured objects called Abstract Syntax Trees (ASTs), separating grammar validation from database execution logic. Each AST struct captures relevant details — such as table name, column definitions, and query conditions — without performing type conversions or storage operations. A follow-up post will cover how these parsed structs are translated into actual bytes written to disk.