diff --git a/docs/howto/analyze.md b/docs/howto/analyze.md
index e7c2c66b41..87541d093e 100644
--- a/docs/howto/analyze.md
+++ b/docs/howto/analyze.md
@@ -106,4 +106,6 @@ reports the result columns and parameters:
 ]
 ```
 
-Pass `--ast` to also include each statement's parsed AST under an `ast` key.
+Pass `--ast` to also include each statement's parsed AST under an `ast` key. It
+has the same shape as the output of [`parse`](parse.md), with every node tagged
+by type.
diff --git a/docs/howto/parse.md b/docs/howto/parse.md
index 2227c1f2b6..623e3b8b90 100644
--- a/docs/howto/parse.md
+++ b/docs/howto/parse.md
@@ -48,6 +48,7 @@ The output is a JSON array with one object per statement:
     "name": "GetAuthor",
     "cmd": ":one",
     "ast": {
+      "tag": "RawStmt",
       "Stmt": {
         "...": "..."
       },
@@ -60,3 +61,49 @@ The output is a JSON array with one object per statement:
 
 Statements without a `-- name:` annotation (for example schema DDL) omit the
 `name` and `cmd` fields.
+
+## Node types
+
+Every node in the AST carries a `tag` naming its type. Some nodes have no
+fields of their own, so without it a star, a null literal and an untranslated
+clause would all print as `{}`.
+
+```json
+"Val": {
+  "tag": "ColumnRef",
+  "Name": "",
+  "Fields": {
+    "tag": "List",
+    "Items": [
+      {
+        "tag": "A_Star"
+      }
+    ]
+  },
+  "Location": 93
+}
+```
+
+A `tag` of `TODO` marks a clause the dialect's converter does not translate
+yet. It means the clause was parsed but is not represented in the AST, not that
+the clause was absent from the query.
+
+## Absent fields
+
+A field the statement does not use is left out rather than printed as `null`.
+An `A_Const` carrying an integer reports only what it has:
+
+```json
+"Val": {
+  "tag": "A_Const",
+  "Val": {
+    "tag": "Integer",
+    "Ival": 1
+  },
+  "Location": 30
+}
+```
+
+Only absent fields are omitted. A zero keeps its place, because zero is a value
+the parser can find: `StmtLocation` is 0 for the first statement in a file, and
+`LIMIT 0` parses to an `Ival` of 0.
diff --git a/internal/endtoend/testdata/analyze_ast/postgresql/stdout.txt b/internal/endtoend/testdata/analyze_ast/postgresql/stdout.txt
index b74264f687..ab257bea23 100644
--- a/internal/endtoend/testdata/analyze_ast/postgresql/stdout.txt
+++ b/internal/endtoend/testdata/analyze_ast/postgresql/stdout.txt
@@ -24,23 +24,28 @@
       }
     ],
     "ast": {
+      "tag": "RawStmt",
       "Stmt": {
+        "tag": "SelectStmt",
         "DistinctClause": {
-          "Items": null
+          "tag": "List"
         },
-        "IntoClause": null,
         "TargetList": {
+          "tag": "List",
           "Items": [
             {
-              "Name": null,
+              "tag": "ResTarget",
               "Indirection": {
-                "Items": null
+                "tag": "List"
               },
               "Val": {
+                "tag": "ColumnRef",
                 "Name": "",
                 "Fields": {
+                  "tag": "List",
                   "Items": [
                     {
+                      "tag": "String",
                       "Str": "name"
                     }
                   ]
@@ -52,32 +57,37 @@
           ]
         },
         "FromClause": {
+          "tag": "List",
           "Items": [
             {
-              "Catalogname": null,
-              "Schemaname": null,
+              "tag": "RangeVar",
               "Relname": "authors",
               "Inh": true,
               "Relpersistence": 112,
-              "Alias": null,
               "Location": 45
             }
           ]
         },
         "WhereClause": {
+          "tag": "A_Expr",
           "Kind": 1,
           "Name": {
+            "tag": "List",
             "Items": [
               {
+                "tag": "String",
                 "Str": "="
               }
             ]
           },
           "Lexpr": {
+            "tag": "ColumnRef",
             "Name": "",
             "Fields": {
+              "tag": "List",
               "Items": [
                 {
+                  "tag": "String",
                   "Str": "id"
                 }
               ]
@@ -85,6 +95,7 @@
             "Location": 59
           },
           "Rexpr": {
+            "tag": "ParamRef",
             "Number": 1,
             "Location": 64,
             "Dollar": true
@@ -92,28 +103,31 @@
           "Location": 62
         },
         "GroupClause": {
-          "Items": null
+          "tag": "List"
+        },
+        "HavingClause": {
+          "tag": "TODO"
         },
-        "HavingClause": {},
         "WindowClause": {
-          "Items": null
+          "tag": "List"
         },
         "ValuesLists": {
-          "Items": null
+          "tag": "List"
         },
         "SortClause": {
-          "Items": null
+          "tag": "List"
+        },
+        "LimitOffset": {
+          "tag": "TODO"
+        },
+        "LimitCount": {
+          "tag": "TODO"
         },
-        "LimitOffset": {},
-        "LimitCount": {},
         "LockingClause": {
-          "Items": null
+          "tag": "List"
         },
-        "WithClause": null,
         "Op": 0,
-        "All": false,
-        "Larg": null,
-        "Rarg": null
+        "All": false
       },
       "StmtLocation": 0,
       "StmtLen": 66
diff --git a/internal/endtoend/testdata/parse_basic/clickhouse/stdout.txt b/internal/endtoend/testdata/parse_basic/clickhouse/stdout.txt
index 28a5ce7e1f..8b2e6a9f56 100644
--- a/internal/endtoend/testdata/parse_basic/clickhouse/stdout.txt
+++ b/internal/endtoend/testdata/parse_basic/clickhouse/stdout.txt
@@ -3,16 +3,18 @@
     "name": "GetValue",
     "cmd": ":one",
     "ast": {
+      "tag": "RawStmt",
       "Stmt": {
-        "DistinctClause": null,
-        "IntoClause": null,
+        "tag": "SelectStmt",
         "TargetList": {
+          "tag": "List",
           "Items": [
             {
-              "Name": null,
-              "Indirection": null,
+              "tag": "ResTarget",
               "Val": {
+                "tag": "A_Const",
                 "Val": {
+                  "tag": "Integer",
                   "Ival": 1
                 },
                 "Location": 31
@@ -21,21 +23,8 @@
             }
           ]
         },
-        "FromClause": null,
-        "WhereClause": null,
-        "GroupClause": null,
-        "HavingClause": null,
-        "WindowClause": null,
-        "ValuesLists": null,
-        "SortClause": null,
-        "LimitOffset": null,
-        "LimitCount": null,
-        "LockingClause": null,
-        "WithClause": null,
         "Op": 0,
-        "All": false,
-        "Larg": null,
-        "Rarg": null
+        "All": false
       },
       "StmtLocation": 0,
       "StmtLen": 32
diff --git a/internal/endtoend/testdata/parse_basic/duckdb/stdout.txt b/internal/endtoend/testdata/parse_basic/duckdb/stdout.txt
index ca847e616a..cae0296ac7 100644
--- a/internal/endtoend/testdata/parse_basic/duckdb/stdout.txt
+++ b/internal/endtoend/testdata/parse_basic/duckdb/stdout.txt
@@ -3,16 +3,18 @@
     "name": "GetValue",
     "cmd": ":one",
     "ast": {
+      "tag": "RawStmt",
       "Stmt": {
-        "DistinctClause": null,
-        "IntoClause": null,
+        "tag": "SelectStmt",
         "TargetList": {
+          "tag": "List",
           "Items": [
             {
-              "Name": null,
-              "Indirection": null,
+              "tag": "ResTarget",
               "Val": {
+                "tag": "A_Const",
                 "Val": {
+                  "tag": "Integer",
                   "Ival": 1
                 },
                 "Location": 30
@@ -21,21 +23,8 @@
             }
           ]
         },
-        "FromClause": null,
-        "WhereClause": null,
-        "GroupClause": null,
-        "HavingClause": null,
-        "WindowClause": null,
-        "ValuesLists": null,
-        "SortClause": null,
-        "LimitOffset": null,
-        "LimitCount": null,
-        "LockingClause": null,
-        "WithClause": null,
         "Op": 0,
-        "All": false,
-        "Larg": null,
-        "Rarg": null
+        "All": false
       },
       "StmtLocation": 0,
       "StmtLen": 33
diff --git a/internal/endtoend/testdata/parse_basic/googlesql/stdout.txt b/internal/endtoend/testdata/parse_basic/googlesql/stdout.txt
index 086f885402..715536dec9 100644
--- a/internal/endtoend/testdata/parse_basic/googlesql/stdout.txt
+++ b/internal/endtoend/testdata/parse_basic/googlesql/stdout.txt
@@ -3,16 +3,18 @@
     "name": "GetValue",
     "cmd": ":one",
     "ast": {
+      "tag": "RawStmt",
       "Stmt": {
-        "DistinctClause": null,
-        "IntoClause": null,
+        "tag": "SelectStmt",
         "TargetList": {
+          "tag": "List",
           "Items": [
             {
-              "Name": null,
-              "Indirection": null,
+              "tag": "ResTarget",
               "Val": {
+                "tag": "A_Const",
                 "Val": {
+                  "tag": "Integer",
                   "Ival": 1
                 },
                 "Location": 30
@@ -21,21 +23,8 @@
             }
           ]
         },
-        "FromClause": null,
-        "WhereClause": null,
-        "GroupClause": null,
-        "HavingClause": null,
-        "WindowClause": null,
-        "ValuesLists": null,
-        "SortClause": null,
-        "LimitOffset": null,
-        "LimitCount": null,
-        "LockingClause": null,
-        "WithClause": null,
         "Op": 0,
-        "All": false,
-        "Larg": null,
-        "Rarg": null
+        "All": false
       },
       "StmtLocation": 0,
       "StmtLen": 31
diff --git a/internal/endtoend/testdata/parse_basic/mssql/stdout.txt b/internal/endtoend/testdata/parse_basic/mssql/stdout.txt
index b20fbdcee5..39e5aa0df6 100644
--- a/internal/endtoend/testdata/parse_basic/mssql/stdout.txt
+++ b/internal/endtoend/testdata/parse_basic/mssql/stdout.txt
@@ -3,16 +3,18 @@
     "name": "GetValue",
     "cmd": ":one",
     "ast": {
+      "tag": "RawStmt",
       "Stmt": {
-        "DistinctClause": null,
-        "IntoClause": null,
+        "tag": "SelectStmt",
         "TargetList": {
+          "tag": "List",
           "Items": [
             {
-              "Name": null,
-              "Indirection": null,
+              "tag": "ResTarget",
               "Val": {
+                "tag": "A_Const",
                 "Val": {
+                  "tag": "Integer",
                   "Ival": 1
                 },
                 "Location": 30
@@ -21,21 +23,8 @@
             }
           ]
         },
-        "FromClause": null,
-        "WhereClause": null,
-        "GroupClause": null,
-        "HavingClause": null,
-        "WindowClause": null,
-        "ValuesLists": null,
-        "SortClause": null,
-        "LimitOffset": null,
-        "LimitCount": null,
-        "LockingClause": null,
-        "WithClause": null,
         "Op": 0,
-        "All": false,
-        "Larg": null,
-        "Rarg": null
+        "All": false
       },
       "StmtLocation": 0,
       "StmtLen": 32
diff --git a/internal/endtoend/testdata/parse_basic/mysql/stdout.txt b/internal/endtoend/testdata/parse_basic/mysql/stdout.txt
index e9ed28784f..5ee2116255 100644
--- a/internal/endtoend/testdata/parse_basic/mysql/stdout.txt
+++ b/internal/endtoend/testdata/parse_basic/mysql/stdout.txt
@@ -3,16 +3,18 @@
     "name": "GetValue",
     "cmd": ":one",
     "ast": {
+      "tag": "RawStmt",
       "Stmt": {
-        "DistinctClause": null,
-        "IntoClause": null,
+        "tag": "SelectStmt",
         "TargetList": {
+          "tag": "List",
           "Items": [
             {
-              "Name": null,
-              "Indirection": null,
+              "tag": "ResTarget",
               "Val": {
+                "tag": "A_Const",
                 "Val": {
+                  "tag": "Integer",
                   "Ival": 1
                 },
                 "Location": 30
@@ -22,26 +24,17 @@
           ]
         },
         "FromClause": {
-          "Items": null
+          "tag": "List"
         },
-        "WhereClause": null,
         "GroupClause": {
-          "Items": null
+          "tag": "List"
         },
-        "HavingClause": null,
         "WindowClause": {
+          "tag": "List",
           "Items": []
         },
-        "ValuesLists": null,
-        "SortClause": null,
-        "LimitOffset": null,
-        "LimitCount": null,
-        "LockingClause": null,
-        "WithClause": null,
         "Op": 0,
-        "All": false,
-        "Larg": null,
-        "Rarg": null
+        "All": false
       },
       "StmtLocation": 0,
       "StmtLen": 31
diff --git a/internal/endtoend/testdata/parse_basic/postgresql/stdout.txt b/internal/endtoend/testdata/parse_basic/postgresql/stdout.txt
index fe35a664c7..deaaea7d6c 100644
--- a/internal/endtoend/testdata/parse_basic/postgresql/stdout.txt
+++ b/internal/endtoend/testdata/parse_basic/postgresql/stdout.txt
@@ -3,20 +3,24 @@
     "name": "GetValue",
     "cmd": ":one",
     "ast": {
+      "tag": "RawStmt",
       "Stmt": {
+        "tag": "SelectStmt",
         "DistinctClause": {
-          "Items": null
+          "tag": "List"
         },
-        "IntoClause": null,
         "TargetList": {
+          "tag": "List",
           "Items": [
             {
-              "Name": null,
+              "tag": "ResTarget",
               "Indirection": {
-                "Items": null
+                "tag": "List"
               },
               "Val": {
+                "tag": "A_Const",
                 "Val": {
+                  "tag": "Integer",
                   "Ival": 1
                 },
                 "Location": 30
@@ -26,32 +30,37 @@
           ]
         },
         "FromClause": {
-          "Items": null
+          "tag": "List"
+        },
+        "WhereClause": {
+          "tag": "TODO"
         },
-        "WhereClause": {},
         "GroupClause": {
-          "Items": null
+          "tag": "List"
+        },
+        "HavingClause": {
+          "tag": "TODO"
         },
-        "HavingClause": {},
         "WindowClause": {
-          "Items": null
+          "tag": "List"
         },
         "ValuesLists": {
-          "Items": null
+          "tag": "List"
         },
         "SortClause": {
-          "Items": null
+          "tag": "List"
+        },
+        "LimitOffset": {
+          "tag": "TODO"
+        },
+        "LimitCount": {
+          "tag": "TODO"
         },
-        "LimitOffset": {},
-        "LimitCount": {},
         "LockingClause": {
-          "Items": null
+          "tag": "List"
         },
-        "WithClause": null,
         "Op": 0,
-        "All": false,
-        "Larg": null,
-        "Rarg": null
+        "All": false
       },
       "StmtLocation": 0,
       "StmtLen": 31
diff --git a/internal/endtoend/testdata/parse_basic/sqlite/stdout.txt b/internal/endtoend/testdata/parse_basic/sqlite/stdout.txt
index c1303a9a1e..50d4c72330 100644
--- a/internal/endtoend/testdata/parse_basic/sqlite/stdout.txt
+++ b/internal/endtoend/testdata/parse_basic/sqlite/stdout.txt
@@ -3,16 +3,18 @@
     "name": "GetValue",
     "cmd": ":one",
     "ast": {
+      "tag": "RawStmt",
       "Stmt": {
-        "DistinctClause": null,
-        "IntoClause": null,
+        "tag": "SelectStmt",
         "TargetList": {
+          "tag": "List",
           "Items": [
             {
-              "Name": null,
-              "Indirection": null,
+              "tag": "ResTarget",
               "Val": {
+                "tag": "A_Const",
                 "Val": {
+                  "tag": "Integer",
                   "Ival": 1
                 },
                 "Location": 30
@@ -22,28 +24,19 @@
           ]
         },
         "FromClause": {
-          "Items": null
+          "tag": "List"
         },
-        "WhereClause": null,
         "GroupClause": {
-          "Items": null
+          "tag": "List"
         },
-        "HavingClause": null,
         "WindowClause": {
-          "Items": null
+          "tag": "List"
         },
         "ValuesLists": {
-          "Items": null
+          "tag": "List"
         },
-        "SortClause": null,
-        "LimitOffset": null,
-        "LimitCount": null,
-        "LockingClause": null,
-        "WithClause": null,
         "Op": 0,
-        "All": false,
-        "Larg": null,
-        "Rarg": null
+        "All": false
       },
       "StmtLocation": 0,
       "StmtLen": 31
diff --git a/internal/sql/ast/json.go b/internal/sql/ast/json.go
new file mode 100644
index 0000000000..cf33cd69d7
--- /dev/null
+++ b/internal/sql/ast/json.go
@@ -0,0 +1,131 @@
+package ast
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"reflect"
+	"strings"
+)
+
+// TagKey is the JSON key under which a node's concrete type is reported.
+//
+// Node is an interface, so the JSON encoding of an AST would otherwise carry no
+// record of which node a given object is. Nodes with no fields (A_Star, Null,
+// TODO) all encode as "{}", and an empty List is indistinguishable from them.
+// Every node object is emitted with this key first, holding the name of its Go
+// type.
+const TagKey = "tag"
+
+var nodeType = reflect.TypeOf((*Node)(nil)).Elem()
+
+// MarshalJSON encodes the statement and every node beneath it, tagging each
+// node object with its type. RawStmt is the root of the AST that the parse and
+// analyze commands print, so implementing it here is enough to tag a whole
+// tree.
+func (n *RawStmt) MarshalJSON() ([]byte, error) {
+	if n == nil {
+		return []byte("null"), nil
+	}
+	return marshalValue(reflect.ValueOf(n))
+}
+
+func marshalValue(v reflect.Value) ([]byte, error) {
+	switch v.Kind() {
+	case reflect.Invalid:
+		return []byte("null"), nil
+
+	case reflect.Interface, reflect.Pointer:
+		if v.IsNil() {
+			return []byte("null"), nil
+		}
+		return marshalValue(v.Elem())
+
+	case reflect.Struct:
+		return marshalStruct(v)
+
+	case reflect.Slice:
+		if v.IsNil() {
+			return []byte("null"), nil
+		}
+		fallthrough
+	case reflect.Array:
+		return marshalArray(v)
+
+	default:
+		// Scalars, strings and anything else encoding/json already handles.
+		return json.Marshal(v.Interface())
+	}
+}
+
+func marshalStruct(v reflect.Value) ([]byte, error) {
+	var buf bytes.Buffer
+	buf.WriteByte('{')
+
+	// A node's Pos method is declared on the pointer type.
+	if reflect.PointerTo(v.Type()).Implements(nodeType) {
+		fmt.Fprintf(&buf, "%q:%q", TagKey, v.Type().Name())
+	}
+
+	t := v.Type()
+	for i := 0; i < t.NumField(); i++ {
+		field := t.Field(i)
+		if !field.IsExported() {
+			continue
+		}
+		name := field.Name
+		if tag, ok := field.Tag.Lookup("json"); ok {
+			tagName, _, _ := strings.Cut(tag, ",")
+			if tagName == "-" {
+				continue
+			}
+			if tagName != "" {
+				name = tagName
+			}
+		}
+		if isNil(v.Field(i)) {
+			continue
+		}
+		value, err := marshalValue(v.Field(i))
+		if err != nil {
+			return nil, err
+		}
+		if buf.Len() > 1 {
+			buf.WriteByte(',')
+		}
+		fmt.Fprintf(&buf, "%q:", name)
+		buf.Write(value)
+	}
+
+	buf.WriteByte('}')
+	return buf.Bytes(), nil
+}
+
+// isNil reports whether a field is absent from the tree, which is the only
+// thing left out of the encoding. Zero-valued scalars are kept: a Location of 0
+// is the start of the file and an Ival of 0 is the literal in "LIMIT 0", so
+// dropping them would lose what the parser found.
+func isNil(v reflect.Value) bool {
+	switch v.Kind() {
+	case reflect.Pointer, reflect.Interface, reflect.Slice, reflect.Map:
+		return v.IsNil()
+	}
+	return false
+}
+
+func marshalArray(v reflect.Value) ([]byte, error) {
+	var buf bytes.Buffer
+	buf.WriteByte('[')
+	for i := 0; i < v.Len(); i++ {
+		if i > 0 {
+			buf.WriteByte(',')
+		}
+		item, err := marshalValue(v.Index(i))
+		if err != nil {
+			return nil, err
+		}
+		buf.Write(item)
+	}
+	buf.WriteByte(']')
+	return buf.Bytes(), nil
+}
diff --git a/internal/sql/ast/tag_test.go b/internal/sql/ast/tag_test.go
new file mode 100644
index 0000000000..3165ca06f2
--- /dev/null
+++ b/internal/sql/ast/tag_test.go
@@ -0,0 +1,49 @@
+package ast
+
+import (
+	"go/ast"
+	"go/parser"
+	"go/token"
+	"strings"
+	"testing"
+)
+
+// TestNoFieldShadowsTagKey guards the JSON encoding in json.go: every node
+// object is emitted with a TagKey key naming its type, so no node may declare a
+// field of its own that collides with it. encoding/json matches field names
+// case-insensitively, so a field named "Tag" would silently capture the tag
+// when the output is decoded back into a node.
+//
+// This is a unit test because the invariant is about the declarations in this
+// package, not about anything sqlc produces. No SQL input can exercise a field
+// that does not exist yet, so the end-to-end tests cannot catch the day someone
+// adds one.
+func TestNoFieldShadowsTagKey(t *testing.T) {
+	fset := token.NewFileSet()
+	pkgs, err := parser.ParseDir(fset, ".", nil, 0)
+	if err != nil {
+		t.Fatalf("parsing package: %s", err)
+	}
+
+	for _, pkg := range pkgs {
+		ast.Inspect(pkg, func(n ast.Node) bool {
+			spec, ok := n.(*ast.TypeSpec)
+			if !ok {
+				return true
+			}
+			structType, ok := spec.Type.(*ast.StructType)
+			if !ok {
+				return true
+			}
+			for _, field := range structType.Fields.List {
+				for _, name := range field.Names {
+					if strings.EqualFold(name.Name, TagKey) {
+						t.Errorf("%s declares a field %q, which collides with the %q key used to tag node types in JSON. Rename the field or pick a different TagKey.",
+							spec.Name.Name, name.Name, TagKey)
+					}
+				}
+			}
+			return true
+		})
+	}
+}