Correct prompt typo + update example for SQLDatabaseChain (#868)

See https://github.com/hwchase17/langchain/issues/821

docs/modules/chains/examples/sqlite.ipynb

@@ -56,6 +56,15 @@
     "llm = OpenAI(temperature=0)"
    ]
   },
+  {
+   "attachments": {},
+   "cell_type": "markdown",
+   "id": "3d1e692e",
+   "metadata": {},
+   "source": [
+    "**NOTE:** For data-sensitive projects, you can specify `return_direct=True` in the `SQLDatabaseChain` initialization to directly return the output of the SQL query without any additional formatting. This prevents the LLM from seeing any contents within the database. Note, however, the LLM still has access to the database scheme (i.e. dialect, table and key names) by default."
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": 3,

langchain/chains/sql_database/prompt.py

@@ -26,7 +26,7 @@ PROMPT = PromptTemplate(
     template=_DEFAULT_TEMPLATE,
 )
 
-_DECIDER_TEMPLATE = """Given the below input question and list of potential tables, output a comma separated list of the table names that may be neccessary to answer this question.
+_DECIDER_TEMPLATE = """Given the below input question and list of potential tables, output a comma separated list of the table names that may be necessary to answer this question.
 
 Question: {query}