Mongo and some corrections

Author: divyagh

clojure.md

@@ -1,5 +1,5 @@
 # Clojure online compiler
-Write, Run & Share Clojure code online using OneCompiler's Clojure online compiler for free. It's one of the robust, feature-rich online compilers for Clojure language, Getting started with the OneCompiler's Clojure editor is easy and fast. The editor shows sample boilerplate code when you choose language as Clojure and you can also choose hundreds of reference programs to get started. For example, if you want to write a program on Clojure collections choose the collections tag from reference and see hundreds of pre-written programs on collections. You can pick one of them to start your coding. 
+Write, Run & Share Clojure code online using OneCompiler's Clojure online compiler for free. It's one of the robust, feature-rich online compilers for Clojure language, Getting started with the OneCompiler's Clojure editor is easy and fast. The editor shows sample boilerplate code when you choose language as Clojure and start coding. Happy learning! 
 
 # Read inputs from stdin
 OneCompiler's Clojure online editor supports stdin and users can give inputs to programs using the STDIN textbox under the I/O tab. Following is a sample Clojure program which takes name as input and prints hello message with your name.

fortran.md

@@ -88,7 +88,7 @@ end if
 
 ### 4. If-Else:
 
-If is used to execute a set of statements based on a condition and execute another set of statements present in else block if condition specified in If block fails.
+If is used to execute a set of statements based on a condition and execute another set of statements present in else block, if condition specified in If block fails.
 
 ```fortran
 if (logical-expression) then     

java.md

@@ -1,5 +1,5 @@
 # Java online compiler
-Write, Run & Share Java code online using OneCompiler's Java online compiler for free. It's one of the robust, feature-rich online compilers for Java language, running the Java LTS version 11. Getting started with the OneCompiler's Java editor is easy and fast. The editor shows sample boilerplate code when you choose language as Java and start coding.
+Write, Run & Share Java code online using OneCompiler's Java online compiler for free. It's one of the robust, feature-rich online compilers for Java language, running the Java LTS version 11. Getting started with the OneCompiler's Java editor is easy and fast. The editor shows sample boilerplate code when you choose language as Java and start coding. Happy learning!
 
 # Taking inputs (stdin)
 OneCompiler's Java online editor supports stdin and users can give inputs to the programs using the STDIN textbox under the I/O tab. Using Scanner class in Java program, you can read the inputs. Following is a sample program that shows reading STDIN ( A string in this case ).

mongodb.md

@@ -0,0 +1,78 @@
+# MongoDB online editor
+Write, Run & Share MongoDB queries online using OneCompiler's MongoDB online editor and compiler for free. It's one of the robust, feature-rich online editor and compiler for MongoDB. Getting started with the OneCompiler's MongoDB editor is really simple and pretty fast. The editor shows sample boilerplate code when you choose language as 'MongoDB' and start writing queries to learn and test online without worrying about tedious process of installation.
+
+# About MongoDB
+
+MongoDB is a cross platform document oriented NoSQL database. 
+
+### Key Features:
+
+* Designed to overcome the the limitations of relational databases approach and other NoSQL solutions
+* Horizontal scaling 
+* Load balancing capabilities
+* Better data availability and stability 
+
+# Syntax help
+
+## Commands
+
+### Inserting documents
+
+1. `db.collection.insert()`: Using `insert` you can either insert one document or array of documents 
+```json
+db.cars.insert({  "name" : "Volvo xc 60",  "type" : "SUV" });
+```
+
+2. `db.collection.insertOne()`: Inserts one document 
+```json
+db.cars.insertOne({  "name" : "Volvo xc 60",  "type" : "SUV" });
+```
+
+3. `db.collection.insertMany`: Inserts multiple documents
+```json
+db.cars.insertMany(
+ [
+   { "name" : "Volvo xc 60",  "type" : "SUV" },
+   { "name" : "Volvo xc 90",  "type" : "SUV" },
+   { "name" : "Volvo S90",  "type" : "SUV" }
+ ]
+);
+```
+
+### Updating documents 
+
+1. `db.collection.update()` : Updates one or more than one document(s) in collection based on matching document and based on `multi` option
+
+```json
+db.cars.update(
+  { type: "SUV" },
+  { $set: { size : 5} },
+  { multi: true}
+)
+```
+2.  `db.collection.updateOne()` : Updates a single document in collection based on matching document 
+```json
+db.cars.updateOne(
+  { type: "SUV" },
+  { $set: { size : 5} }
+)
+```
+3.  `db.collection.updateMany()` : Updates multiple documents in collection based on the condition.
+```json
+db.cars.updateMany(
+  { type: "hatchback" },
+  { $set: { size : 5} }
+)
+```
+
+### Deleting documents
+
+1. `db.collection.deleteOne(<filter>, <options>)`: Deletes a Single document from collection
+```json
+db.employees.deleteOne({_id: 1})
+```
+
+2. `db.collection.deleteMany(<filter>, <options>)`: Deletes all documents with matching filter
+```json
+db.employees.deleteMany({type: "hatchback"})
+```

mysql.md

@@ -20,33 +20,6 @@ MySQL is a open-source, free and very popular relational database management sys
 
 ## Commands
 
-### Creating a database
-
-```sql
-CREATE DATABASE [IF NOT EXISTS] db_name;
-```
-### Use a database
-
-```sql
-USE db_name;
-```
-### Drop a database
-
-```sql
-DROP DATABASE [IF EXISTS] db_name;
-```
-### Show available databases in the working database server
-
-```sql
-SHOW DATABASE;
-```
-### Display all the tables present in the database
-
-```sql
-SHOW TABLES;
-```
-##  DDL Commands
-
 ### 1. CREATE 
 
 ```sql
@@ -55,10 +28,24 @@ CREATE TABLE table_name (
                 column2 datatype,
                 ....);
 ``` 
+
+### Example
+```sql
+CREATE TABLE EMPLOYEE (
+  empId INTEGER PRIMARY KEY,
+  name TEXT NOT NULL,
+  dept TEXT NOT NULL
+);
+```
 ### 2. ALTER
 ```sql 
 ALTER TABLE Table_name ADD column_name datatype;
 ```
+
+### Example
+```sql
+INSERT INTO EMPLOYEE VALUES (0001, 'Dave', 'Sales');
+```
 ### 3. TRUNCATE
 ```sql
 TRUNCATE table table_name;
@@ -91,58 +78,41 @@ INSERT INTO table_name (column1, column2, column3, ...) VALUES (value1, value2,
 ```
 Note: Column names are optional.
 
+### Example
+```sql
+INSERT INTO EMPLOYEE VALUES (0001, 'Ava', 'Sales');
+```
 ### 2. SELECT 
 
 ```sql
 SELECT column1, column2, ...
 FROM table_name
 [where condition]; 
 ```
+
+### Example
+```sql
+SELECT * FROM EMPLOYEE where dept ='sales';
+```
 ### 3. UPDATE 
 
 ```sql
 UPDATE table_name
 SET column1 = value1, column2 = value2, ...
 WHERE condition; 
 ```
+### Example
+```sql
+UPDATE EMPLOYEE SET dept = 'Sales' WHERE empId='0001'; 
+```
 ### 4. DELETE 
 
 ```sql 
 DELETE FROM table_name where condition;
 ```
-
-## DCL Commands
-
-### 1. GRANT
-
-```sql
-GRANT privileges ON object TO user;
-```
-### 2. REVOKE
-
-```sql
-REVOKE privileges ON object FROM user;
-```
-## TCL commands
-
-### 1. COMMIT
-
-```sql
-COMMIT;
-```
-### 2. ROLLBACK  
-
-```sql
-ROLLBACK;
-```
-## 3. SAVEPOINT
-```sql
-SAVEPOINT savepoint_name;
-ROLLBACK TO savepoint_name; 
-```
-How to delete a savepoint:
+### Example
 ```sql
-RELEASE SAVEPOINT savepoint_name;
+DELETE from EMPLOYEE where empId='0001'; 
 ```
 
 ## Indexes