diff --git a/datasette/app.py b/datasette/app.py
index 19d708f4..8852b036 100644
--- a/datasette/app.py
+++ b/datasette/app.py
@@ -243,6 +243,8 @@ class DatabaseView(BaseView):
     template = 'database.html'
 
     async def data(self, request, name, hash):
+        if request.args.get('sql'):
+            return await self.custom_sql(request, name, hash)
         tables = []
         table_metadata = self.ds.metadata()[name]['tables']
         for table_name, table_rows in table_metadata.items():
@@ -265,6 +267,25 @@ class DatabaseView(BaseView):
             'database_hash': hash,
         }
 
+    async def custom_sql(self, request, name, hash):
+        params = request.raw_args
+        sql = params.pop('sql')
+        validate_sql_select(sql)
+        rows = await self.execute(name, sql, params)
+        columns = [r[0] for r in rows.description]
+        return {
+            'database': name,
+            'rows': rows,
+            'columns': columns,
+            'query': {
+                'sql': sql,
+                'params': params,
+            }
+        }, {
+            'database_hash': hash,
+            'custom_sql': True,
+        }
+
 
 class DatabaseDownload(BaseView):
     async def view_get(self, request, name, hash, **kwargs):
diff --git a/datasette/static/app.css b/datasette/static/app.css
index fa8e6fde..b5559447 100644
--- a/datasette/static/app.css
+++ b/datasette/static/app.css
@@ -73,3 +73,34 @@ th {
     margin-top: 1em;
     margin-bottom: 0;
 }
+
+form.sql textarea {
+    border: 1px solid #ccc;
+    width: 70%;
+    height: 3em;
+    padding: 4px;
+    font-family: monospace;
+    font-size: 1.3em;
+}
+@media only screen and (max-width: 576px) {
+    form.sql textarea {
+        width: 95%;
+    }
+}
+form.sql p {
+    margin: 0;
+}
+form.sql input[type=submit] {
+    color: #fff;
+    background-color: #007bff;
+    border-color: #007bff;
+    font-weight: 400;
+    cursor: pointer;
+    text-align: center;
+    vertical-align: middle;
+    border: 1px solid blue;
+    padding: .275rem .75rem;
+    font-size: 1rem;
+    line-height: 1.5;
+    border-radius: .25rem;
+}
diff --git a/datasette/templates/database.html b/datasette/templates/database.html
index adaa8fd9..607d836e 100644
--- a/datasette/templates/database.html
+++ b/datasette/templates/database.html
@@ -3,7 +3,7 @@
 {% block title %}{{ database }}{% endblock %}
 
 {% block content %}
-<div class="hd"><a href="/">home</a></div>
+<div class="hd"><a href="/">home</a>{% if query %} / <a href="/{{ database }}-{{ database_hash }}">{{ database }}</a>{% endif %}</div>
 
 <h1 style="padding-left: 10px; border-left: 10px solid #{{ database_hash[:6] }}">{{ database }}</h1>
 
@@ -13,6 +13,11 @@
     <p><a href="/{{ database }}-{{ database_hash }}.db">download {{ database }}.db</a></p>
 {% endif %}
 
+<form class="sql" action="/{{ database }}-{{ database_hash }}" method="get">
+    <p><textarea name="sql">{% if query and query.sql %}{{ query.sql }}{% else %}select * from {{ tables[0].name }}{% endif %}</textarea></p>
+    <p><input type="submit" value="Run SQL"></p>
+</form>
+
 {% for table in tables %}
 <div class="db-table">
     <h2><a href="/{{ database }}-{{ database_hash }}/{{ table.name }}">{{ table.name }}</a></h2>
diff --git a/tests/test_app.py b/tests/test_app.py
index d6c1e7df..5fab6c32 100644
--- a/tests/test_app.py
+++ b/tests/test_app.py
@@ -34,6 +34,40 @@ def test_database_page(three_table_app_client):
     assert response.status == 302
     _, response = three_table_app_client.get('/three_tables')
     assert 'three_tables' in response.text
+    # Test JSON list of tables
+    _, response = three_table_app_client.get('/three_tables.json')
+    data = response.json
+    assert 'three_tables' == data['database']
+    assert [{
+        'columns': ['pk1', 'pk2', 'content'],
+        'name': 'compound_primary_key',
+        'table_rows': 0
+    }, {
+        'columns': ['content'],
+        'name': 'no_primary_key',
+        'table_rows': 0,
+    }, {
+        'columns': ['pk', 'content'],
+        'name': 'simple_primary_key',
+        'table_rows': 2
+    }] == data['tables']
+
+
+def test_custom_sql(three_table_app_client):
+    _, response = three_table_app_client.get(
+        '/three_tables.jsono?sql=select+content+from+simple_primary_key'
+    )
+    data = response.json
+    assert {
+        'sql': 'select content from simple_primary_key',
+        'params': {}
+    } == data['query']
+    assert [
+        {'content': 'hello'},
+        {'content': 'world'}
+    ] == data['rows']
+    assert ['content'] == data['columns']
+    assert 'three_tables' == data['database']
 
 
 def test_table_page(three_table_app_client):