add insert, update, delete and join

insert-update-delete.md

@@ -0,0 +1,34 @@
+#INSERT INTO Syntax
+
+It is possible to write the INSERT INTO statement in two ways.
+
+The first way specifies both the column names and the values to be inserted:
+
+example-: INSERT INTO table_name (column1, column2, column3, ...)
+          VALUES (value1, value2, value3, ...);
+
+If you are adding values for all the columns of the table, you do not need to specify the column names in the SQL query.
+However, make sure the order of the values is in the same order as the columns in the table. The INSERT INTO syntax would be as follows:
+
+example-: INSERT INTO table_name
+          VALUES (value1, value2, value3, ...);
+
+
+#The SQL UPDATE Statement
+
+The UPDATE statement is used to modify the existing records in a table.
+
+UPDATE Syntax-:
+
+example-: UPDATE table_name
+          SET column1 = value1, column2 = value2, ...
+          WHERE condition;
+
+
+#The SQL DELETE Statement
+
+The DELETE statement is used to delete existing records in a table.
+
+DELETE Syntax-:
+example-: DELETE FROM table_name WHERE condition;
+

join.md

@@ -0,0 +1,47 @@
+#JOIN
+A JOIN clause is used to combine rows from two or more tables, based on a related column between them.
+
+SELECT Orders.OrderID, Customers.CustomerName, Orders.OrderDate
+FROM Orders
+INNER JOIN Customers ON Orders.CustomerID=Customers.CustomerID;
+
+Different Types of SQL JOINs
+Here are the different types of the JOINs in SQL:
+
+1. (INNER) JOIN: Returns records that have matching values in both tables.
+  example-SELECT column_name(s)
+          FROM table1
+          INNER JOIN table2
+          ON table1.column_name = table2.column_name;
+
+2. LEFT (OUTER) JOIN: Returns all records from the left table, and the matched records from the right table.
+   example-SELECT column_name(s)
+            FROM table1
+            LEFT JOIN table2
+            ON table1.column_name = table2.column_name;
+
+3. RIGHT (OUTER) JOIN: Returns all records from the right table, and the matched records from the left table.
+   example-SELECT column_name(s)
+            FROM table1
+            RIGHT JOIN table2
+            ON table1.column_name = table2.column_name;
+
+4. FULL (OUTER) JOIN: Returns all records when there is a match in either left or right table.
+   example-SELECT column_name(s)
+            FROM table1
+            FULL OUTER JOIN table2
+            ON table1.column_name = table2.column_name
+            WHERE condition;
+
+#SQL Self JOIN
+A self JOIN is a regular join, but the table is joined with itself.
+
+Self JOIN Syntax:
+
+  SELECT column_name(s)
+  FROM table1 T1, table1 T2
+  WHERE condition;
+
+  T1 and T2 are different table aliases for the same table.
+
+