create table: column constraints — NOT NULL / UNIQUE / DEFAULT grammar (ADR-0029)

`create table … with pk` now parses the column-constraint
suffix; combined with the commit-1 db layer, a constrained
table works end to end.

- A shared constraint-suffix grammar fragment — `not null`,
  `unique`, `default <literal>` — sits after each column's
  `(type)` group; `build_create_table` walks the matched path
  per column and folds the constraints into `ColumnSpec`.
- §9 redundancy check: every `with pk` column is a primary-key
  column, so `not null` (any) and `unique` (single-column PK)
  are rejected with a friendly error
  (`parse.custom.constraint_redundant_on_pk`).
- `project.yaml` round-trip: `ColumnSchema` gains `not_null` /
  `default`; the YAML reader/writer and `build_read_schema`
  carry them, so `rebuild` / `export` / `import` preserve
  constraints.
- ADR-0029 §2.1's example corrected — `create table` columns
  are all PK columns, so its suffix is for `default` / `check`;
  `docs/simple-mode-limitations.md` records that non-PK
  columns at create time need advanced mode.

CHECK is deferred to the next commit. 1184 tests pass (+7);
clippy clean.

docs/adr/0029-column-constraints.md

@@ -80,14 +80,24 @@ A column spec gains an optional, repeatable constraint suffix
 **after** the `(type)` group:
 
 ```
-create table Users with pk
+create table Books with pk isbn(text) check (length(isbn) = 13)
-  id(serial),
-  email(text) not null unique,
-  age(int) default 18 check (age >= 0)
 
-add column to Orders: note (text) default ''
+add column to Books: title (text) not null
+add column to Books: stock (int) default 0 check (stock >= 0)
 ```
 
+**Where each constraint is useful.** The simple-mode `create
+table … with pk …` declares *only* primary-key columns —
+every column in the `with pk` list is part of the primary key
+(non-PK columns are added afterward with `add column`; see
+`docs/simple-mode-limitations.md`). Since a PK column is
+already `NOT NULL` and `UNIQUE`, §9 rejects those two as
+redundant there — so on a `create table` column the suffix is
+useful for `default` / `check`. `not null` / `unique` come
+into their own on `add column` (non-PK columns) and on `add
+constraint`. The suffix grammar is nonetheless shared
+verbatim across all three surfaces; §9 does the rejecting.
+
 - Standard SQL writes constraints after the data type
   (`email TEXT NOT NULL UNIQUE`). The playground brackets the
   type as `email(text)` — a pre-existing convention this ADR

docs/simple-mode-limitations.md

@@ -38,3 +38,13 @@ entry names the ADR that drew the boundary.
   yet available.
 - **No `LIMIT … OFFSET`** — `limit` takes a row count
   only.
+
+## Table creation (ADR-0029)
+
+- **`create table` declares only primary-key columns.**
+  `create table T with pk …` makes every listed column part
+  of the primary key; there is no simple-mode syntax for a
+  non-PK column in the same statement. Non-PK columns are
+  added afterward with `add column`. Creating a table with a
+  mix of PK and non-PK columns in one statement needs
+  advanced-mode `CREATE TABLE` syntax.

src/db.rs

@@ -1610,6 +1610,8 @@ fn read_schema_snapshot(conn: &Connection) -> Result<SchemaSnapshot, DbError> {
             .map(|c| ColumnSchema {
                 name: c.name.clone(),
                 unique: c.unique,
+                not_null: c.notnull,
+                default: c.default_sql.clone(),
                 // user_type is always populated for tables we
                 // created; the fallback is defensive.
                 user_type: c.user_type.unwrap_or(Type::Text),
@@ -1703,6 +1705,8 @@ fn read_table_snapshot(
             name: c.name.clone(),
             user_type: c.user_type.unwrap_or(Type::Text),
             unique: c.unique,
+            not_null: c.notnull,
+            default: c.default_sql.clone(),
         })
         .collect();
     let column_idents: Vec<String> = read
@@ -5361,10 +5365,10 @@ fn build_read_schema(table: &TableSchema, relationships: &[RelationshipSchema])
         .map(|c| ReadColumn {
             name: c.name.clone(),
             sqlite_type: c.user_type.sqlite_strict_type().to_string(),
-            notnull: false,
+            notnull: c.not_null,
             primary_key: table.primary_key.contains(&c.name),
             unique: c.unique,
-            default_sql: None,
+            default_sql: c.default.clone(),
             user_type: Some(c.user_type),
         })
         .collect();

src/dsl/grammar/data.rs

@@ -375,7 +375,10 @@ fn require_ident(path: &MatchedPath, role: &'static str) -> Result<String, Valid
 /// Convert a `MatchedItem` whose kind is one of the `value_literal`
 /// variants (Word("null"|"true"|"false"), NumberLit, StringLit) to
 /// a `Value`. Returns None for non-value items.
-fn item_to_value(item: &MatchedItem) -> Option<Value> {
+///
+/// `pub(crate)` so `grammar::ddl` can reuse it when collecting a
+/// `default <literal>` column constraint (ADR-0029).
+pub(crate) fn item_to_value(item: &MatchedItem) -> Option<Value> {
     match &item.kind {
         MatchedKind::Word("null") => Some(Value::Null),
         MatchedKind::Word("true") => Some(Value::Bool(true)),

src/dsl/grammar/ddl.rs

@@ -820,6 +820,37 @@ const COL_NAME: Node = Node::Hinted {
     inner: &COL_NAME_IDENT,
 };
 
+// ADR-0029 column-constraint suffix — `not null`, `unique`,
+// `default <literal>`. (`check (<expr>)` joins in a later
+// ADR-0029 step.) One shared fragment: `create table` uses it
+// here; `add column` and `add constraint` reuse it later.
+const NOT_NULL_NODES: &[Node] = &[
+    Node::Word(Word::keyword("not")),
+    Node::Word(Word::keyword("null")),
+];
+const NOT_NULL_CONSTRAINT: Node = Node::Seq(NOT_NULL_NODES);
+
+const UNIQUE_CONSTRAINT: Node = Node::Word(Word::keyword("unique"));
+
+const DEFAULT_CONSTRAINT_NODES: &[Node] = &[
+    Node::Word(Word::keyword("default")),
+    super::shared::FALLBACK_VALUE_LITERAL,
+];
+const DEFAULT_CONSTRAINT: Node = Node::Seq(DEFAULT_CONSTRAINT_NODES);
+
+const COLUMN_CONSTRAINT_CHOICES: &[Node] =
+    &[NOT_NULL_CONSTRAINT, UNIQUE_CONSTRAINT, DEFAULT_CONSTRAINT];
+const COLUMN_CONSTRAINT: Node = Node::Choice(COLUMN_CONSTRAINT_CHOICES);
+
+/// Zero-or-more constraints — the suffix after a column's
+/// `(type)` group (ADR-0029 §2.1). `min: 0` so an
+/// unconstrained column still matches.
+const COLUMN_CONSTRAINT_SUFFIX: Node = Node::Repeated {
+    inner: &COLUMN_CONSTRAINT,
+    separator: None,
+    min: 0,
+};
+
 const COL_SPEC_NODES: &[Node] = &[
     COL_NAME,
     Node::Punct('('),
@@ -833,6 +864,7 @@ const COL_SPEC_NODES: &[Node] = &[
         writes_user_listed_column: false,
     },
     Node::Punct(')'),
+    COLUMN_CONSTRAINT_SUFFIX,
 ];
 const COL_SPEC: Node = Node::Seq(COL_SPEC_NODES);
 
@@ -858,64 +890,114 @@ const CREATE_TABLE_NODES: &[Node] = &[
 ];
 const CREATE_TABLE: Node = Node::Seq(CREATE_TABLE_NODES);
 
+/// The friendly error for declaring a constraint a
+/// primary-key column already implies (ADR-0029 §9).
+fn redundant_pk_constraint(column: &str, constraint: &str) -> ValidationError {
+    ValidationError {
+        message_key: "parse.custom.constraint_redundant_on_pk",
+        args: vec![
+            ("column", column.to_string()),
+            ("constraint", constraint.to_string()),
+        ],
+    }
+}
+
 fn build_create_table(path: &MatchedPath) -> Result<Command, ValidationError> {
     let name = require_ident(path, "table_name")?;
 
-    // Collect column specs by pairing alternating col_name /
+    // Walk the matched items, segmenting per column: a
-    // col_type ident matches. They always appear in declaration
+    // `col_name` ident stashes the name, the following
-    // order so a simple zip is correct.
+    // `col_type` ident finalises the spec, and the constraint
-    let names: Vec<String> = path
+    // tokens after it (ADR-0029 §2.1) attach to that spec.
-        .items
+    let mut columns: Vec<ColumnSpec> = Vec::new();
-        .iter()
+    let mut pending_name: Option<String> = None;
-        .filter_map(|i| match &i.kind {
+    let mut items = path.items.iter().peekable();
-            MatchedKind::Ident { role: "col_name", .. } => Some(i.text.clone()),
+    while let Some(item) = items.next() {
-            _ => None,
+        match &item.kind {
-        })
+            MatchedKind::Ident { role: "col_name", .. } => {
-        .collect();
+                pending_name = Some(item.text.clone());
-    let types_raw: Vec<&str> = path
+            }
-        .items
+            MatchedKind::Ident { role: "col_type", .. } => {
-        .iter()
+                let ty = item.text.parse::<Type>().map_err(|_| ValidationError {
-        .filter_map(|i| match &i.kind {
+                    message_key: "parse.error_wrapper",
-            MatchedKind::Ident { role: "col_type", .. } => Some(i.text.as_str()),
+                    args: vec![("detail", "unknown type".to_string())],
-            _ => None,
+                })?;
-        })
+                let col_name = pending_name.take().ok_or_else(|| ValidationError {
-        .collect();
+                    message_key: "parse.error_wrapper",
+                    args: vec![("detail", "column type without a name".to_string())],
+                })?;
+                columns.push(ColumnSpec::new(col_name, ty));
+            }
+            // `not null` — the grammar's `Seq` guarantees a
+            // `null` Word follows a matched `not` Word.
+            MatchedKind::Word("not") => {
+                if matches!(
+                    items.peek().map(|i| &i.kind),
+                    Some(MatchedKind::Word("null"))
+                ) {
+                    items.next();
+                    if let Some(last) = columns.last_mut() {
+                        last.not_null = true;
+                    }
+                }
+            }
+            MatchedKind::Word("unique") => {
+                if let Some(last) = columns.last_mut() {
+                    last.unique = true;
+                }
+            }
+            // `default <literal>` — the `Seq` guarantees a value
+            // item follows a matched `default` Word.
+            MatchedKind::Word("default") => {
+                let value = items
+                    .next()
+                    .and_then(crate::dsl::grammar::data::item_to_value)
+                    .ok_or_else(|| ValidationError {
+                        message_key: "parse.error_wrapper",
+                        args: vec![("detail", "default needs a value".to_string())],
+                    })?;
+                if let Some(last) = columns.last_mut() {
+                    last.default = Some(value);
+                }
+            }
+            _ => {}
+        }
+    }
 
     // No PK clause OR `with pk` alone (no specs): if `with` was
-    // matched, default to id:serial; otherwise reject with the
+    // matched, default to id(serial); otherwise reject with the
-    // "tables need at least one column" friendly wording.
+    // "tables need a primary key" friendly wording.
-    let saw_with = path
+    if columns.is_empty() {
-        .items
+        let saw_with = path
-        .iter()
+            .items
-        .any(|i| matches!(i.kind, MatchedKind::Word("with")));
+            .iter()
-
+            .any(|i| matches!(i.kind, MatchedKind::Word("with")));
-    let pk_specs: Vec<(String, Type)> = if names.is_empty() {
         if saw_with {
-            // `with pk` alone — default to id(serial).
+            columns.push(ColumnSpec::new("id", Type::Serial));
-            vec![("id".to_string(), Type::Serial)]
         } else {
             return Err(ValidationError {
                 message_key: "parse.custom.create_table_needs_pk",
                 args: vec![],
             });
         }
-    } else {
+    }
-        let mut out = Vec::with_capacity(names.len());
-        for (n, t_str) in names.iter().zip(types_raw.iter()) {
-            let ty = t_str.parse::<Type>().map_err(|_| ValidationError {
-                message_key: "parse.error_wrapper",
-                args: vec![("detail", "unknown type".to_string())],
-            })?;
-            out.push((n.clone(), ty));
-        }
-        out
-    };
 
-    let columns = pk_specs
+    // Every `with pk` column is part of the primary key
-        .iter()
+    // (ADR-0029 §2.1). A PK column is already NOT NULL, and a
-        .map(|(n, t)| ColumnSpec::new(n.clone(), *t))
+    // single-column PK is already UNIQUE — declaring those
-        .collect();
+    // explicitly is a friendly error, not a silent no-op
-    let primary_key = pk_specs.into_iter().map(|(n, _)| n).collect();
+    // (ADR-0029 §9).
+    let single_column_pk = columns.len() == 1;
+    for col in &columns {
+        if col.not_null {
+            return Err(redundant_pk_constraint(&col.name, "NOT NULL"));
+        }
+        if col.unique && single_column_pk {
+            return Err(redundant_pk_constraint(&col.name, "UNIQUE"));
+        }
+    }
+
+    let primary_key = columns.iter().map(|c| c.name.clone()).collect();
 
     Ok(Command::CreateTable {
         name,
@@ -930,3 +1012,69 @@ pub static CREATE: CommandNode = CommandNode {
     ast_builder: build_create_table,
     help_id: Some("ddl.create"),
     usage_ids: &["parse.usage.create_table"],};
+
+// =================================================================
+// Tests — `create table` column constraints (ADR-0029 §2.1, §9)
+// =================================================================
+
+#[cfg(test)]
+mod constraint_tests {
+    use super::Command;
+    use crate::dsl::command::ColumnSpec;
+    use crate::dsl::parser::parse_command;
+    use crate::dsl::value::Value;
+
+    /// Parse a `create table` and return its column specs.
+    fn create_columns(input: &str) -> Vec<ColumnSpec> {
+        match parse_command(input).expect("create table should parse") {
+            Command::CreateTable { columns, .. } => columns,
+            other => panic!("expected CreateTable, got {other:?}"),
+        }
+    }
+
+    #[test]
+    fn create_table_parses_a_text_default() {
+        // `grade` is the (single) PK column; `default` is
+        // allowed on a PK column (ADR-0029 §9).
+        let cols = create_columns("create table T with pk grade(text) default 'A'");
+        assert_eq!(cols.len(), 1);
+        assert_eq!(cols[0].default, Some(Value::Text("A".to_string())));
+        assert!(!cols[0].not_null && !cols[0].unique);
+    }
+
+    #[test]
+    fn create_table_parses_a_numeric_default_on_a_compound_pk_member() {
+        let cols = create_columns("create table T with pk a(int), b(int) default 7");
+        assert_eq!(cols.len(), 2);
+        assert_eq!(cols[1].default, Some(Value::Number("7".to_string())));
+    }
+
+    #[test]
+    fn not_null_on_a_pk_column_is_a_redundancy_error() {
+        // Every `create table` column is a primary-key column,
+        // so `not null` is always redundant there (ADR-0029 §9).
+        assert!(parse_command("create table T with pk id(serial) not null").is_err());
+    }
+
+    #[test]
+    fn unique_on_a_single_column_pk_is_a_redundancy_error() {
+        assert!(parse_command("create table T with pk code(text) unique").is_err());
+    }
+
+    #[test]
+    fn unique_on_a_compound_pk_member_is_allowed() {
+        // A compound PK does not make its members individually
+        // unique, so an explicit `unique` is meaningful there.
+        let cols = create_columns("create table T with pk a(int) unique, b(text)");
+        assert_eq!(cols.len(), 2);
+        assert!(cols[0].unique, "`a` carries an explicit UNIQUE");
+        assert!(!cols[1].unique);
+    }
+
+    #[test]
+    fn an_unconstrained_create_table_still_parses() {
+        let cols = create_columns("create table T with pk id(serial), name(text)");
+        assert_eq!(cols.len(), 2);
+        assert!(cols.iter().all(|c| !c.not_null && !c.unique && c.default.is_none()));
+    }
+}

src/dsl/grammar/shared.rs

@@ -354,7 +354,10 @@ const FALLBACK_VALUE_LITERAL_INNER: Node = Node::Choice(FALLBACK_VALUE_LITERAL_C
 /// surface the generic "Type a value: number, 'text', …" prose
 /// here rather than the misleading `null`/`true`/`false`
 /// candidate trio.
-const FALLBACK_VALUE_LITERAL: Node = Node::Hinted {
+/// The schemaless value-literal slot. `pub(crate)` so the
+/// `default <literal>` column constraint (ADR-0029) can reuse
+/// it from `grammar::ddl`.
+pub(crate) const FALLBACK_VALUE_LITERAL: Node = Node::Hinted {
     mode: HintMode::ProseOnly("hint.value_literal_slot"),
     inner: &FALLBACK_VALUE_LITERAL_INNER,
 };

src/friendly/keys.rs

@@ -189,6 +189,7 @@ pub const KEYS_AND_PLACEHOLDERS: &[(&str, &[&str])] = &[
     // by the DSL parser. See `parse.custom.*` in the catalog.
     ("parse.custom.bind_type_mismatch", &["found", "expected"]),
     ("parse.custom.change_column_flags_exclusive", &[]),
+    ("parse.custom.constraint_redundant_on_pk", &["column", "constraint"]),
     ("parse.custom.create_table_needs_pk", &[]),
     ("parse.custom.expression_too_deep", &[]),
     ("parse.custom.insert_form_a_missing_values", &["columns"]),

src/friendly/strings/en-US.yaml

@@ -398,6 +398,10 @@ parse:
     # classifies the input as mid-typing rather than
     # dispatching a logically-empty Form C insert.
     insert_form_a_missing_values: "`insert into ...({columns})` looks like Form A — add `values (...)` to supply the matching values."
+    # ADR-0029 §9: a primary-key column is already NOT NULL,
+    # and a single-column primary key is already UNIQUE —
+    # declaring either explicitly is redundant.
+    constraint_redundant_on_pk: "`{column}` is a primary-key column, so it is already {constraint} — drop the redundant constraint."
   # Caret pointer showing where in the input the parser
   # failed. `{padding}` is the leading whitespace; the
   # template appends `^` so the rendered line places the

src/persistence/csv_io.rs

@@ -370,7 +370,13 @@ mod tests {
     use crate::persistence::ColumnSchema;
 
     fn col(name: &str, ty: Type) -> ColumnSchema {
-        ColumnSchema { name: name.to_string(), user_type: ty, unique: false }
+        ColumnSchema {
+            name: name.to_string(),
+            user_type: ty,
+            unique: false,
+            not_null: false,
+            default: None,
+        }
     }
 
     #[test]

src/persistence/mod.rs

@@ -145,6 +145,13 @@ pub struct ColumnSchema {
     /// save/load cycle. Defaults to `false` when missing in
     /// older project files.
     pub unique: bool,
+    /// `NOT NULL` constraint (ADR-0029). Defaults to `false`
+    /// when missing in older project files.
+    pub not_null: bool,
+    /// `DEFAULT` expression as a SQL literal (ADR-0029) — the
+    /// form SQLite reports and `schema_to_ddl` echoes verbatim.
+    /// `None` when the column has no default.
+    pub default: Option<String>,
 }
 
 /// One index as recorded in `project.yaml` (ADR-0025).
@@ -374,6 +381,8 @@ mod tests {
                 name: "Name".to_string(),
                 user_type: Type::Text,
                 unique: false,
+                not_null: false,
+                default: None,
             }],
             rows: vec![vec![CellValue::Text("Alice".to_string())]],
         };

src/persistence/yaml.rs

@@ -92,22 +92,45 @@ fn write_table(out: &mut String, table: &TableSchema) {
     }
 }
 
-fn write_column(out: &mut String, col: &ColumnSchema) {
+/// Always render `s` as a double-quoted YAML string — used
-    if col.unique {
+/// for a column's `default` SQL literal, which must round-trip
-        let _ = writeln!(
+/// as a string even when it looks numeric (ADR-0029).
-            out,
+fn yaml_string(s: &str) -> String {
-            "      - {{ name: {}, type: {}, unique: true }}",
+    let mut out = String::with_capacity(s.len() + 2);
-            quote_if_needed(&col.name),
+    out.push('"');
-            col.user_type.keyword(),
+    for c in s.chars() {
-        );
+        match c {
-    } else {
+            '"' => out.push_str("\\\""),
-        let _ = writeln!(
+            '\\' => out.push_str("\\\\"),
-            out,
+            '\n' => out.push_str("\\n"),
-            "      - {{ name: {}, type: {} }}",
+            _ => out.push(c),
-            quote_if_needed(&col.name),
+        }
-            col.user_type.keyword(),
-        );
     }
+    out.push('"');
+    out
+}
+
+fn write_column(out: &mut String, col: &ColumnSchema) {
+    let mut line = format!(
+        "      - {{ name: {}, type: {}",
+        quote_if_needed(&col.name),
+        col.user_type.keyword(),
+    );
+    // ADR-0018 / ADR-0029 constraint flags — emitted only when
+    // set, so an unconstrained column stays a compact two-field
+    // entry and older readers stay forward-compatible.
+    if col.unique {
+        line.push_str(", unique: true");
+    }
+    if col.not_null {
+        line.push_str(", not_null: true");
+    }
+    if let Some(default) = &col.default {
+        line.push_str(", default: ");
+        line.push_str(&yaml_string(default));
+    }
+    line.push_str(" }");
+    let _ = writeln!(out, "{line}");
 }
 
 fn write_relationship(out: &mut String, rel: &RelationshipSchema) {
@@ -213,6 +236,8 @@ pub(crate) fn parse_schema(body: &str) -> Result<SchemaSnapshot, YamlError> {
                 name: c.name,
                 user_type,
                 unique: c.unique,
+                not_null: c.not_null,
+                default: c.default,
             });
         }
         tables.push(TableSchema {
@@ -339,6 +364,12 @@ struct RawColumn {
     /// field default to `false`.
     #[serde(default)]
     unique: bool,
+    /// `NOT NULL` flag (ADR-0029); absent in older files.
+    #[serde(default)]
+    not_null: bool,
+    /// `DEFAULT` SQL literal (ADR-0029); absent in older files.
+    #[serde(default)]
+    default: Option<String>,
 }
 
 #[derive(Deserialize)]
@@ -376,16 +407,16 @@ mod tests {
                     name: "Customers".to_string(),
                     primary_key: vec!["id".to_string()],
                     columns: vec![
-                        ColumnSchema { name: "id".to_string(), user_type: Type::Serial, unique: false },
+                        ColumnSchema { name: "id".to_string(), user_type: Type::Serial, unique: false, not_null: false, default: None },
-                        ColumnSchema { name: "Name".to_string(), user_type: Type::Text, unique: false },
+                        ColumnSchema { name: "Name".to_string(), user_type: Type::Text, unique: false, not_null: false, default: None },
                     ],
                 },
                 TableSchema {
                     name: "Orders".to_string(),
                     primary_key: vec!["id".to_string()],
                     columns: vec![
-                        ColumnSchema { name: "id".to_string(), user_type: Type::Serial, unique: false },
+                        ColumnSchema { name: "id".to_string(), user_type: Type::Serial, unique: false, not_null: false, default: None },
-                        ColumnSchema { name: "CustId".to_string(), user_type: Type::Int, unique: false },
+                        ColumnSchema { name: "CustId".to_string(), user_type: Type::Int, unique: false, not_null: false, default: None },
                     ],
                 },
             ],
@@ -451,6 +482,8 @@ mod tests {
                     name: "yes".to_string(),
                     user_type: Type::Bool,
                     unique: false,
+                    not_null: false,
+                    default: None,
                 }],
             }],
             relationships: vec![],
@@ -474,6 +507,47 @@ mod tests {
         assert_eq!(parsed, original);
     }
 
+    #[test]
+    fn column_constraints_round_trip_through_yaml() {
+        // NOT NULL / UNIQUE / DEFAULT survive a serialize →
+        // parse cycle (ADR-0029 §7).
+        let snap = SchemaSnapshot {
+            created_at: "2026-05-19T00:00:00Z".to_string(),
+            tables: vec![TableSchema {
+                name: "Books".to_string(),
+                primary_key: vec!["isbn".to_string()],
+                columns: vec![
+                    ColumnSchema {
+                        name: "isbn".to_string(),
+                        user_type: Type::Text,
+                        unique: false,
+                        not_null: false,
+                        default: None,
+                    },
+                    ColumnSchema {
+                        name: "title".to_string(),
+                        user_type: Type::Text,
+                        unique: true,
+                        not_null: true,
+                        default: Some("'untitled'".to_string()),
+                    },
+                    ColumnSchema {
+                        name: "stock".to_string(),
+                        user_type: Type::Int,
+                        unique: false,
+                        not_null: false,
+                        default: Some("0".to_string()),
+                    },
+                ],
+            }],
+            relationships: vec![],
+            indexes: vec![],
+        };
+        let body = serialize_schema(&snap);
+        let parsed = parse_schema(&body).expect("parse schema");
+        assert_eq!(parsed, snap, "constraints survive the yaml round-trip");
+    }
+
     #[test]
     fn parses_minimal_yaml_with_no_tables() {
         let body = "\
@@ -548,8 +622,8 @@ relationships:
                 name: "Items".to_string(),
                 primary_key: vec!["a".to_string(), "b".to_string()],
                 columns: vec![
-                    ColumnSchema { name: "a".to_string(), user_type: Type::Int, unique: false },
+                    ColumnSchema { name: "a".to_string(), user_type: Type::Int, unique: false, not_null: false, default: None },
-                    ColumnSchema { name: "b".to_string(), user_type: Type::Int, unique: false },
+                    ColumnSchema { name: "b".to_string(), user_type: Type::Int, unique: false, not_null: false, default: None },
                 ],
             }],
             relationships: vec![],