Merge pull request #3539 from Apoorva-Atre/newbranch

Added DML.md in DBMS

Author: ajay-dhangar

docs/DBMS/Structured Query Language/dml.md

@@ -0,0 +1,78 @@
+# Data Manipulation Language
+
+DML is used for performing non-structural updates to a database. For example, adding a row to an existing table, retrieving data from a table, etc.
+
+### DML commands include:
+- Select
+- Insert 
+- Update
+- Delete
+
+Let's see each command in detail:
+
+## select
+
+This command is used to retrieve data from the database. It is generally followed by from and where clauses.
+
+Example:
+```sql
+select * from customers;
+```
+This query will return all the rows from the table customers including all attributes (columns).
+
+```sql
+select * 
+from customers 
+where address="India";
+```
+This query will return all the rows where the address of the customer is India.
+
+```sql
+select name,address
+from customers;
+```
+This type of query returns only the name and address of the customers, i.e. the required information, instead of returning all the information. 
+
+## insert
+
+The insert command is used to add rows to a table in the database.
+
+Example:
+```sql
+insert into customers values("Riya","India");
+```
+We can also insert multiple rows at a time:
+```sql
+insert into customers values
+("Riya","India")
+("Aditya","India")
+("Chris","Germany");
+```
+
+## update
+
+This command is used to update a certain row, given some information about that row.
+
+Example:
+```sql
+update customers
+set name="Tanisha"
+where customer_id=125;
+```
+This query would update the name of the customer with id=125 to Tanisha.
+
+## delete
+
+Delete command is used to delete some rows in the table.
+
+Example:
+```sql
+delete from customers where customer_id=125;
+```
+This will delete all the information of customer with id=125.
+
+We can also delete multiple rows at a time:
+```sql
+delete from customers where address="India";
+```
+This query would delete information of all customers from India.