Drizzle ORM

Schema Written in TypeScript

Drizzle keeps the schema in ordinary TypeScript files, so the compiler checks it before anything touches a database:

import { pgTable, serial, text } from "drizzle-orm/pg-core";

export const users = pgTable("users", {
  id: serial("id").primaryKey(),
  email: text("email").notNull().unique(),
});

export type User = typeof users.$inferSelect;
export type NewUser = typeof users.$inferInsert;

$inferSelect and $inferInsert derive row types straight from the table definition — no code generation step between editing a column and getting autocomplete. drizzle-kit push applies the schema to a live database (prototyping), while drizzle-kit generate emits SQL migration files your team reviews and applies in CI.

Query Builder and Relational Reads

The builder mirrors SQL structure while staying fully typed:

const rows = await db
  .select()
  .from(users)
  .where(eq(users.email, "a@b.c"))
  .innerJoin(posts, eq(posts.authorId, users.id));

await db.insert(users).values({ email: "x@y.z" }).returning();

Pass the schema into drizzle(db, { schema }) to unlock relational queries: db.query.users.findMany({ with: { posts: true } }) compiles to an efficient joined fetch and types the nested result. Joins, returning(), and onConflictDoUpdate all produce inferred row shapes, so a bad column name is a compile error rather than a runtime 500.

Pitfalls and Interview Angles

push versus generate. push mutates the database immediately and can drop data on destructive diffs — fine locally, wrong for shared environments. Teams commit generate output so migrations are reviewable.

Dialect APIs differ. drizzle-orm/pg-core, mysql2, and sqlite-core expose different column builders; porting means rewriting the schema, not just the connection string.

Values stay parameters. eq(users.email, input) binds the value as a query parameter, so user input cannot rewrite SQL — the same property raw template strings would break.

Interview: contrast Drizzle's inferred types with Prisma's generated client, and explain why a typed builder still needs runtime validation at the HTTP boundary.