# Overview

<Anatomy call="schema" shape="object" exported>
  <AnatomyPart slot="tables" label="Tables" code="tables: [notes]," mark="required">
    The list, in the order you write it. A reference names a table in this list, earlier or later. [`table()`](/docs/define/table) only stores the columns. Names and the catalog hash are fixed here. Calling `schema()` twice on the same tables returns equal catalog bytes.
  </AnatomyPart>
  <AnatomyPart slot="sections" label="Pages" code="…," mark="sections">
    Each other field is a page in this group.
  </AnatomyPart>
</Anatomy>

## The declaration

Each option is a page. Tables come first, because every other option refers to them.

| Order | Page | You use it for |
| --- | --- | --- |
| 1 | [Tables](/docs/define/schema/tables) | The list `schema()` compiles. |
| 2 | [Casing](/docs/define/schema/casing) | The SQL name of a camelCase field. |
| 3 | [Codecs](/docs/define/schema/codecs) | The TypeScript value. The SQL type stays. |
| 4 | [Row types](/docs/define/schema/types) | Emitted types, or types kept in the checker. |
| 5 | [Id default](/docs/define/schema/defaults) | What a bare `t.id()` means. |
| 6 | [Minimum Postgres](/docs/define/schema/min-postgres) | The oldest major. Omitted means 15. |
| 7 | [Traits](/docs/define/schema/traits) | Columns added to every table. |
| 8 | [Tenancy](/docs/define/schema/tenancy) | Tenant keys on every table. |
| 9 | [Validation](/docs/define/schema/validation) | Whether rules run. |
| 10 | [Extensions](/docs/define/schema/extensions) | Extensions the catalog names. |
| 11 | [Functions](/docs/define/schema/functions) | Routines the catalog stores. |
| 12 | [Triggers](/docs/define/schema/triggers) | Triggers that call those functions. |
| 13 | [Views](/docs/define/schema/views) | Views and materialized views. |
| 14 | [Several catalogs](/docs/define/schema/catalogs) | `external()`, a snapshot, and one history per namespace. |