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Oracle DBA Scenario Based Interview Questions
Oracle DBA Scenario Based Interview Questions
Q1. The main function(s) of the redo log is?
Ans. Redo log’s main function is to store all changes made to the database as they occur.
Q2. What are the contents of the control file?
Every Oracle database has a control file. A control file is a small binary file that records the physical structure of the database and includes:
- The database name
- Names and locations of associated datafiles and online redo log files
- The timestamp of the database creation
- The current log sequence number
- Checkpoint information
Q3. What are the advantages of the control file?
Ans. The control file must be available for writing by the Oracle database server whenever the database is open. Without the control file, the database cannot be mounted and recovery is difficult. You might also need to create control files if you want to change particular settings in the control files.
Q4. What is the definition of SQL?
Ans. SQL is a database computer language designed for managing data in relational database management systems (RDBMS) and originally based upon relational algebra. Its scope includes data insert, query, update and delete, schema creation and modification, and data access control.
Q5. What is the use of the SELECT statement?
Ans. The SELECT statement is used to select the set of specific values from a table in a database depending on the various conditions specified in a SQL query.
Q6. How can you compare a part of the name rather than the entire name?
Ans. In order to compare parts, we use the LIKE operator which acts like a regex engine for a database.
Q7. What is the keyword to get distinct records from a table?
Ans. SELECT DISTINCT allows the user to select the distinct values from a table in a database.
Q8. In order to get sorted records from a table, what is the keyword?
Ans. ORDER BY keyword is used for sorting the results. It returns the sorted results to your program.
Q9. In order to get total records from a table, what is the keyword?
Ans. To find the total number of records in a table, the COUNT keyword is used.
Q10. What is the definition of GROUP BY?
Ans. GROUP BY keyword is an aggregate function such as SUM, MULTIPLE, etc and without this function sum for each individual group value can not be calculated.
Q11. Explain the difference between “dropping a table”, “truncating a table” and “deleting all records” from a table?
Ans.
- Dropping a table means dropping the invalid indexes. It deletes table definition and records both,
- Truncating means deleting invalid data values automatically. Internally the database marks the table as empty and the deleted records are not recorded in the transaction log.
- Deleting all records, deletes all records but records all details in a Transaction log file.
Q12. Different types of SQL statements are?
Ans.
There are five types of SQL statements
- Data Definition Language
- Data Manipulation Language,
- Transactional Control,
- Session Control and
- System Control.
Q13. What is the definition of the transaction?
Ans. Oracle supports transactions as defined by the SQL standard. A transaction is a sequence of SQL statements that Oracle treats as a single unit of work. As soon as you connect to the database, a transaction begins. Once the transaction begins, every SQL DML (Data Manipulation Language) statement you issue subsequently becomes a part of this transaction. A transaction ends when you disconnect from the database, or when you issue a COMMIT or ROLLBACK command.
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Oracle DBA Training Scenario Based Interview Questions