So yesterday I said about all my day but not discussed what I learn yesterday so in SQL class previously we were learning about constraints and types of constraints among that three were over unique check after this yesterday we learn about primary key and foreign key so next heading primary ke it is used to identify the unique records from the table next heading characteristics of primary key first point we have only one primary Ken in a table next point primary key cannot accept duplicate or repeated values next point primary key cannot accept null values next point primary key is a combination of unique and notinal constraints next point primary key is not mandatory but it is highly recommended to use in a table next heading foreign key it is used to establish connection between the tables next heading characteristics of foreign key next point we have n number of foreign keys in a table exponent foreign key can accept duplicate or repeated values next point foreign key can accept null values next point foreign key is not the combination of unique and not constraints next point for an attribute to be a foreign key it must be primary key in its own table next point foreign key present in child table but it actually belongs to parent table next point foreign key is also known as reference integrity constraint. This much we have discussed with few examples and in Java willownt about variable and its declaration and initialisation will get into depth of that and tomorrow’s blog and that’s it this is what we learn to study thank you