Oracle Interview Questions and Answers
ORACLE is primarily a relational database management system. Oracle is also known as Oracle DB or Oracle RDMS. By using Oracle, the user can directly access the objects through the Structured Query Language(SQL).
Oracle is designed to support multiple data models. The best part about Oracle is that it has its network component which allows the communications across the networks. Oracle runs on Windows, UNIX, Linux, and Mac OS. Oracle is written in Assembly language, C & C++.in today's world Oracle database is considered as one of the most reliable database engines in the world. Oracle interview questions we are mentioning below will help you to gain enough of the knowledge about Oracle.
Most Frequently Asked Oracle Interview Questions
The compound trigger was in introduced in Oracle 11g. This single trigger on a table enables the user to specify the actions for each of the four timing points:
- Before the firing statement
- Before each row that the firing statement affects
- After each row that the firing statement changes
- After the firing statement
In other words, Compound trigger merges all the four triggering events into the single piece of code, and as a result, the performance of the database server is improved during the bulk operations. The Compound trigger is only for the DML triggers.
The translate function replaces the characters in a string with the new set of characters one by one. For example:- the first character in the string is replaced by the first character of the original string and so on. The translate function always returns a string value.
Syntax:-
TRANSLATE( string1, string_to_replace, replacement_string )
String1:-the string which has to be replaced
string_to_replace:-the string that has to be searched in the string 1
replacement_string:-the new string with which string1 will be replaced.
Once the table is created, then the user can add any value in the table, but the values have to be validated. In this case, the constraints act as a validator which checks the data validity.
There are five types of constraints:-
- NOT NULL:-The column will not accept the NULL value
- UNIQUE:-It will check whether the record entered is unique or not.
- PRIMARY:-The column will have a value, and it will be unique. In a table, only one primary key should be there.
- CHECK:-when the user wants the record in the column to be of a particular type.
- FOREIGN KEY:-to relate more than one table that means matching the value of one table with that of another table.
Drop constraint is used for removing the constraints from the table.
Syntax:-
ALTER TABLE table_name
DROP CONSTRAINT constraint_name
For example:- if the table name is INTERVIEW. QUESTIONS and the constraint name is TEST_ CONST
ALTER TABLE INTERVIEW. QUESTIONS
DROP CONSTRAINT TEST_ CONST
Dynamic SQL is the programming methods in which the SQL statements are constructed at the run time. Dynamic SQL is used when there is a requirement of the DDL(database definition language) statements while writing the programs or when the user is not aware of the compilation time of the SQL statement.
When the data required by the user is in more than one table, then Join comes into the picture. Oracle Join is used to combine the rows from more than one tables. Join also retrieves data from multiple tables and creates a new table.
Left join returns all the records from the left-hand side of the table which is specified in the ON condition, only those records from the right table where the join condition is met.
syntax:-
SELECT columns
FROM table1
LEFT JOIN table2
ON table1.column = table2.column;
Here is the syntax:-
SELECT columns
FROM table1
INNER JOIN table2
ON table1.column = table2.column;
An Inner join is also called a simple join, and it is the mostly used join.
Development History
- Flashback Technology recovers the data which is lost or deleted efficiently
- Reliable even when the tasks are demanding
- Manages a large amount of data
- Has the capability to maintain multiple databases.
All your questions related to Oracle will be answered in the Oracle interview questions for freshers mentioned below.
Development History
Oracle was developed by Lawrence Ellison and his co-workers Bob Miner and Ed Oates in the year 1977. The first version ORACLEv2 was released in the year 1979 which was the first available SQL based RDBMS.
Latest Version
Oracle Database 18c is the newest version which got released on 16th February 2018.