Oracle interview FAQs

What is a Database Listener?

A: Database listening is part of the background process for the database to start. It is a necessary condition for the normal operation of the database, similar to human being;

Database startup sequence?

A: Create a database, start a database instance, and load a database.

How do I configure the database server?

A: tnsnames in the database installation directory (E: \ app \ Administrator \ product \ 11.1.0 \ db_1 \ NETWORK \ ADMIN. modify HOST (Server IP address) and PORT (corresponding PORT) in the ora File

The two tables cannot be updated or modified. How can I locate them?

A: 1. Restart the database. 2. The tables and tables may be locked and must be unlocked. 3. Restart various database services.

What is a port?

A: A port refers to the unique port used for communication between the network and the network.

What background processes are involved when the database is started?

A: service process and listening process

What is a database instance? What are the components?

A: The database instance is a collection of background processes and database files.

Which database version have you used?

Answer: For oracle11G

The database cannot be started. Why?

Answer: Network and installation reasons

The database client cannot connect to the server. Why? Three reasons

A: 1. Server File configuration error; 2. Listening service not started; 3. incorrect user name and password

 

Cursor is a data buffer provided by the system for users to store the execution results of SQL statements. Each cursor area has a name. You can use SQL statements to obtain records from the cursor one by one and assign them to the primary variables for further processing in the primary language. The main language for editing this database is record-oriented. A group of primary variables can only store one record at a time. Using only primary variables does not fully meet the requirements for SQL statements to output data to applications. Embedded SQL introduces the cursor concept to coordinate these two different processing methods. During database development, when the data you retrieve is only one record, the transaction statement code you write usually uses the select insert statement. However, we often encounter this situation, that is, reading a record from a result set one by one. How can this problem be solved? Cursors provide us with an excellent solution. Cursors and cursors are an important concept in databases. A cursor provides a flexible means to operate the data retrieved from a table. In essence, A cursor is actually a mechanism that can extract a record from a result set that contains multiple data records. A cursor is always associated with an SQL selection statement because it is a result set (it can be zero, one, or multiple records retrieved by the relevant selection statement) and the cursor position in the result set pointing to a specific record. When processing a result set, a cursor pointing to the result set must be declared. If you have written a program to process a file in C language, the cursor is like the file handle you get when you open the file. If the file is successfully opened, the file handle can represent the file. For a cursor, the principle is the same. The visible cursor can process the result set from the basic table in a similar way as the traditional program reads the flat file, so as to present the data in the table to the program in the form of a flat file. We know that the relational database management system is actually set-oriented. In ms SQL SERVER, there is no way to describe a single record in a table, unless you use the where clause to limit that only one record is selected. Therefore, we must use a cursor to process a single record. The cursor allows the application to perform the same or different operations on each row in the row result set returned by the select statement, rather than performing the same operation on the entire result set at a time; it also provides the ability to delete or update table data based on the cursor position. In addition, it is the combination of the cursor as a collection-oriented database management system and row-oriented programming, enable communication between the two data processing methods.

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