rename "Missing Values" to "Default Values"

book/03-schema-design/015-missing-values.ipynb → book/03-schema-design/015-default-values.ipynb

@@ -87,7 +87,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "# Null values\n",
+    "# Understanding Null values\n",
     "\n",
     "In database design, the null value holds a special significance and follows special rules.\n",
     "It represents the absence of a value or the intentional omission of an attribute's data.\n",
@@ -100,18 +100,14 @@
     "\n",
     "Using null as a default value in table declarations can be a strategic choice for handling optional or unknown data.\n",
     "\n",
-    "## Understanding null\n",
     "The null value is not equivalent to zero, an empty string, or any other placeholder; rather, it explicitly signifies that the data is missing or undefined. This can be crucial in scientific databases, where the distinction between \"no data\" and \"zero\" or \"empty\" is meaningful.\n",
     "\n",
     "## Benefits of Using null as a Default Value\n",
     "**Flexibility**: By setting null as the default value, you allow for flexibility in data entry. This is particularly useful when some attributes may not always be applicable or when the data for an attribute might not be available at the time of record creation.\n",
     "\n",
     "**Data Integrity**: Using null helps maintain the integrity of the data by preventing the entry of arbitrary or placeholder values when the actual data is unknown or inapplicable. This avoids misleading or inaccurate entries in the database.\n",
     "\n",
-    "**Clear Semantics**: null clearly indicates the absence of a value, distinguishing it from cases where a value of zero, an empty string, or another default might be misleading. This clarity can be important for both data entry and data analysis.\n",
-    "\n",
-    "## Implementing null as a Default Value in DataJoint\n",
-    "In DataJoint, you can specify `null` as a default value in the table declaration. Here’s an example:"
+    "**Clear Semantics**: null clearly indicates the absence of a value, distinguishing it from cases where a value of zero, an empty string, or another default might be misleading. This clarity can be important for both data entry and data analysis."
    ]
   },
   {