Main difference between Primary key and Foreign key in a table is that, it’s the same column which behaves as primary key in parent table and as foreign key in child table. For example in Customer and Orderrelationship, customer_id is primary key in Customer table but foreign key in Order table. By the way what is foreign key in a table and difference between Primary and Foreign key are some of the popular SQL interview questions, much like truncate vs delete in SQL or difference between correlated and noncorrelated subquery. We have been learning key SQL concepts along with these frequently asked SQL questions and in this SQL tutorial we will discuss about what is foreign key in SQL and purpose of foreign key in any table. By the way this is the third article related to primary key in SQL, other being difference between primary and unique key and How to find second highest salary in SQL. If you are preparing for any technical job interview where you expect some SQL questions, check out these questions, they are worth preparing.
Tampilkan postingan dengan label vs. Tampilkan semua postingan
Tampilkan postingan dengan label vs. Tampilkan semua postingan
Selasa, 18 Februari 2014
Difference between Primary key vs Foreign key in table – SQL database tutorial
Read more »
Kamis, 06 Februari 2014
fail safe vs fail fast Iterator in Java
Difference between fail-safe and fail-fast Iterator is becoming favorite core java interview questions day by day, reason
it touches concurrency a bit and interviewee can go deep on it to ask how fail-safe or fail-fast behavior is implemented.
In this article article we will see what is fail-safe and fail fast iterators in java and differences between fail-fast and fail-safe iterators . Concept of fail-safe iterator are relatively new in Java and first introduced with Concurrent Collections in Java 5 like ConcurrentHashMap and CopyOnWriteArrayList.