fixed typos and sequence

Author: sourabhbagrecha

docs/20-prerequisites/20-prerequisite.mdx

@@ -6,7 +6,7 @@ description: Setting up your MongoDB Atlas account, importing Library data
 
 To follow along, you'll need to complete the first two labs of the MongoDB for RDBMS professionals. Which will help you in getting:
 
-- MongoDB Atlas Cluster
-- Test data. In this case, this is book, author, and review data for a library management system.
+- A free MongoDB Atlas Cluster
+- Sample data
 
-👐 To get both, open the [intro lab](https://mongodb-developer.github.io/intro-lab/docs/intro) and follow it (only takes 10-15 mins) to get your database ready. Return here when finished!
+To get both, open the [intro lab](https://mongodb-developer.github.io/intro-lab/docs/intro) and follow it (only takes 10-15 mins) to get your database ready. Return here when finished!

docs/50-aggregation/3-sort-limit.mdx

@@ -77,7 +77,7 @@ SELECT * FROM books ORDER BY timestamp DESC LIMIT 5;
     ```js
       db.books.aggregate([
         {
-          $match: { year: {$lt: 2010}}
+          $match: { year: {$gt: 2010}}
         },
         {
           $project: {

docs/50-aggregation/4-group.mdx

@@ -91,52 +91,59 @@ db.books.aggregate([
 
 ---
 
-## 👐 Example 3: Find the Average Book Rating of all books
+## 👐 Example 3: Find the total number of pages published every year.
 
 ### **MongoDB Query**
 
 ```js
-db.reviews.aggregate([
-  { $group: { _id: "$bookId", avgRating: { $avg: "$rating" } } },
+db.books.aggregate([
+  {
+    $group: {
+      _id: "$year",
+      totalPages: { $sum: "$pages" },
+    },
+  },
 ]);
 ```
 
 ### Equivalent SQL Query
 
 ```sql
-SELECT bookId, AVG(rating) AS avgRating
-FROM reviews
-GROUP BY bookId;
+SELECT year, SUM(rating) AS totalPages
+FROM books
+GROUP BY year;
 ```
 
 ### Sample Output
 
 ```json
 [
-  { "_id": "1885865171", "avgRating": 4.2 },
-  { "_id": "0738701688", "avgRating": 4.33 },
-  { "_id": "0747545448", "avgRating": 5 }
+  { "_id": 1955, "totalPages": 664 },
+  { "_id": 1952, "totalPages": 416 },
+  { "_id": 1899, "totalPages": 128 }
+  ...
 ]
 ```
 
 ---
 
 ## 👐 Challenge
 
-### 👐 1. Find the total number of pages published every year.
+### 👐 1. Find the Average Book Rating of all books
 
 <details>
   <summary>Answer</summary>
     ```js
-    db.books.aggregate([
+    db.reviews.aggregate([
       {
         $group: {
-          _id: "$year",
-          totalPages: { $sum: "$pages" }
+          _id: "$bookId",
+          avgRating: { $avg: "$rating" }
         }
       },
     ]);
     ```
+
 </details>
 
 ### 👐 2. Find users with the most number of reviews. Hint: Use the `name` field in the reviews collection.

docs/50-aggregation/5-JOIN.mdx

@@ -47,14 +47,6 @@ db.authors.aggregate([
 ]);
 ```
 
-### **Equivalent SQL Query**
-
-```sql
-SELECT books.*, authors.*
-FROM authors
-LEFT JOIN books ON authors._id = books.author_id;
-```
-
 :::info
 The result in MongoDB will have an array (`authorDetails`) instead of flat columns.
 :::

docs/50-aggregation/7-CREATE-VIEW.mdx

@@ -1,4 +1,4 @@
-# 👐 $merge
+# 🦸 $merge
 
 In MongoDB, the **$merge** stage allows you to **write the results of an aggregation pipeline into a new or existing collection**. This is similar to the concept of "INSERT INTO ... SELECT" or "MERGE INTO" in SQL databases.