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These are some interview question and answer asked during my recent interview. Oracle interview questions are very important during any programming job interview . Interviewer always want to check how comfortable we are with any database either we go for Java developer position or C, C++ programmer position .So here I have discussed some basic question related with oracle database. Apart from these questions which is very specific to Oracle database you may find some general questions related to database fundamentals and SQL e.g. Difference between correlated and noncorrelated subquery in database or truncate vs delete in SQL etc. Some of the most important topics in Oracle Interview questions are SQL, date, inbuilt function, stored procedure and less used features like cursor, trigger and views. These questions also gives an idea about formats of questions asked during Oracle Interview. Read more �

The main difference between Primary key and Foreign key in a table is that it�s the same column which behaves as primary key in the parent table and as a foreign key in a child table. For example in Customer and Order relationship, customer_id is the primary key in Customer table but a foreign key in Order table. By the way, what is a 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 what is a foreign key in SQL and purpose of the foreign key in any table. By the way, this is the third article related to a 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 e...

Many time we need SQL query which return data page by page i.e. 30 or 40 records at a time, which can be specified as page size. In fact Database pagination is common requirement of Java web developers, especially dealing with largest data sets. In this article we will see how to query Oracle 10g database for pagination or how to retrieve data using paging from Oracle. Many Java programmer also use display tag for paging in JSP which supports both internal and external paging. In case of internal paging all data is loaded in to memory in one shot and display tag handles pagination based upon page size but it only suitable for small data where you can afford those many objects in memory. If you have hundreds of row to display than its best to use external pagination by asking database to do pagination. In pagination, ordering is another important aspect which can not be missed. It�s virtually impossible to sort large collection in Java using Comparator or Comparable bec ause of limite...

How to add column in existing table with default value is another popular SQL interview question asked for Junior level programming job interviews . Though syntax of SQL query to add column with default value varies little bit from database to database, it always been performed using ALTER keyword of ANSI SQL. Adding column in existing table in MySQL database is rather easy and straight forward and we will see example of SQL query for MySQL database which adds a column with default value. You can also provide constraints like NULL or NOT NULL while adding new column in table. In this SQL tutorial we are adding third column in a table called Contacts which contains name and phone of contacts. Now we want to add another column email with default value "abc@yahoo.com". We will use ALTER command in SQL to do that. By the way this is next in our SQL tutorials e.g. How to join three tables in SQL and SQL query to find duplicate records in table . If you haven't read them ye...

Some time we need to split a long comma separated String in Stored procedure e.g. Sybase or SQL Server stored procedures. Its quite common to pass comma delimited or delimiter separated String as input parameter to Stored procedure and than later split comma separated String into multiple values inside stored proc. This is not just case of input parameter but you can also have comma separated string in any table data. Unfortunately there is no split() function in Sybase or SQL Server 2005 or 2008 which can directly split string based on delimiter just like in Java string split method . Fortunately Sybase Adaptive Server and Microsoft SQL server has functions like CHARINDEX and PATINDEX which can be used to split comma separated String. This is next on our SQL tutorials after seeing SQL query to find duplicate records in table and How to find 2 nd and Nth maximum salary in SQL . Read more �

How to find second highest or second maximum salary of an Employee is one of the most frequently asked SQL interview question similar to finding duplicate records in table and when to use truncate vs delete . T here are many ways to find second highest salary based upon which database you are using as different database provides different feature which can be used to find second maximum or Nth maximum salary of employee. Well this question can also be generalized with other scenario like finding second maximum age etc. In this SQL tutorial we will see different example of SELECT SQL query to find second highest salary independent of databases or you may call in ANSI SQL and other SQL queries which uses database specific feature to find second maximum salary. Read more �

How to find duplicate records in table is a popular SQL interview question which has been asked as many times as difference between truncate and delete in SQL or finding second highest salary of employee. Both of these SQL queries are must know for any one who is appearing on any programming interview where some questions on database and SQL are expected. In order to find duplicate records in database table you need to confirm definition of duplicates, for example in below contact table which is suppose to store name and phone number of contact, a record is considered to be duplicate if both name and phone number is same but unique if either of them varies. Problem of duplicates in database arise when you don't have a primary key or unique key on database and that's why its recommended to have a key column in table. Anyway its easy to find duplicate records in table by using group by clause of ANSI SQL. Group by clause is used to group data based upon any column or a nu...

Three table JOIN Example SQL Joining three tables in single SQL query can be very tricky if you are not good with the concept of SQL Join. SQL Joins have always been tricky not only for new programmers but for many others, who are in programming and SQL for more than 2 to 3 years. There are enough to confuse someone on SQL JOIN ranging from various types of SQL JOIN like INNER and OUTER join, LEFT and RIGHT outer join, CROSS join etc. Between all of these fundamentals, What is most important about Join is, combining multiple tables. If you need data from multiple tables in one SELECT query you need to use either subquery or JOIN. Most of the times we only join two tables like Employee and Department but sometimes you may require joining more than two tables and a popular case is joining three tables in SQL. In the case of joining three tables table, 1 relates to table 2 and then table 2 relates to table 3. If you look at closely you find that table 2 is a joining table whi...