What is index in DBA?

An index is a schema object that contains an entry for each value that appears in the indexed column(s) of the table or cluster and provides direct, fast access to rows. Oracle Database supports several types of index: Normal indexes. (By default, Oracle Database creates B-tree indexes.)

What is index in database and its types?

Indexing is a small table which is consist of two columns. Two main types of indexing methods are 1)Primary Indexing 2) Secondary Indexing. Primary Index is an ordered file which is fixed length size with two fields. The primary Indexing is also further divided into two types 1)Dense Index 2)Sparse Index.

What is an index in Oracle?

An index is a database structure that provides quick lookup of data in a column or columns of a table. For example, a Flights table in a travelDB database has three indexes: An index on the orig_airport column (called OrigIndex)

What is index and key?

A key (minimal superkey) is a set of attributes, the values of which are unique for every tuple (every row in the table at some point in time). An index is a performance optimisation feature that enables data to be accessed faster.

What is cursor in SQL?

Introduction. A cursor in SQL is a temporary work area created in system memory when a SQL statement is executed. A SQL cursor is a set of rows together with a pointer that identifies a current row. It is a database object to retrieve data from a result set one row at a time.

What is create view in SQL?

In SQL, a view is a virtual table based on the result-set of an SQL statement. A view contains rows and columns, just like a real table. The fields in a view are fields from one or more real tables in the database.

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How do I run a cursor in Oracle?

How to use Explicit Cursor?
  1. DECLARE the cursor in the Declaration section.
  2. OPEN the cursor in the Execution Section.
  3. FETCH the data from the cursor into PL/SQL variables or records in the Execution Section.
  4. CLOSE the cursor in the Execution Section before you end the PL/SQL Block.

What is a surrogate key in database?

A surrogate key is a unique key for an entity in the client’s business or for an object in the database. Sometimes natural keys cannot be used to create a unique primary key of the table. This is when the data modeler or architect decides to use surrogate or helping keys for a table in the LDM.

How do I index a column in MySQL?

To create indexes, use the CREATE INDEX command: CREATE INDEX index_name ON table_name (column_name); You can an index on multiple columns.

How do I create a subquery in SQL?

SQL – Sub Queries
  1. Subqueries must be enclosed within parentheses.
  2. A subquery can have only one column in the SELECT clause, unless multiple columns are in the main query for the subquery to compare its selected columns.
  3. An ORDER BY command cannot be used in a subquery, although the main query can use an ORDER BY.

How do I make MySQL read only?

MySQL doesn’t support WITH READ ONLY for CREATE VIEW . The line DEFINER = CURRENT_USER is not needed if you use the limited user to create the view. Or you can use an admin user to create the view and in this case the line DEFINER = must contain the name of the user that will own the view.

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How do I delete a view in MySQL?

To delete a view, use the DROP VIEW command. DROP VIEW takes one argument: the name of the view to be dropped. A database name can be prepended to the view name. You can add the IF EXISTS syntax.

What is cursor in MySQL?

MySQL cursor is a kind of loop facility given to traverse in the result of SQL one by one. We can operate on every result by using the cursor in MySQL. Cursors are supported in stored procedures, functions, and triggers only. MySQL cursor is available from version 5 or greater.

What is a function in Plsql?

A stored function (also called a user function or user-defined function) is a set of PL/SQL statements you can call by name. Stored functions are very similar to procedures, except that a function returns a value to the environment in which it is called. User functions can be used as part of a SQL expression.

What is normalization in SQL?

Normalization is the process of organizing data in a database. This includes creating tables and establishing relationships between those tables according to rules designed both to protect the data and to make the database more flexible by eliminating redundancy and inconsistent dependency.

What is a composite key in SQL?

A composite key in SQL can be defined as a combination of multiple columns, and these columns are used to identify all the rows that are involved uniquely. Even though a single column can’t identify any row uniquely, a combination of over one column can uniquely identify any record.

How do you create an index in Word?

Create the index
  1. Click where you want to add the index.
  2. On the References tab, in the Index group, click Insert Index.
  3. In the Index dialog box, you can choose the format for text entries, page numbers, tabs, and leader characters.
  4. You can change the overall look of the index by choosing from the Formats dropdown menu.

How many types of joins in MySQL?

There are three types of MySQL joins: MySQL INNER JOIN (or sometimes called simple join) MySQL LEFT OUTER JOIN (or sometimes called LEFT JOIN) MySQL RIGHT OUTER JOIN (or sometimes called RIGHT JOIN)

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What is SQL Indexing?

A SQL index is used to retrieve data from a database very fast. Indexing a table or view is, without a doubt, one of the best ways to improve the performance of queries and applications. A SQL index is a quick lookup table for finding records users need to search frequently.

How can we insert data into a view?

You can insert data through a single-table view if you have the Insert privilege on the view. To do this, the defining SELECT statement can select from only one table, and it cannot contain any of the following components: DISTINCT keyword. GROUP BY clause.

How do I delete a MySQL user?

Deleting a MySQL Account
  1. First, connect to the MySQL database as the root user: mysql -u root -p. …
  2. Enter the password when prompted and hit Enter. …
  3. Find the exact name of the user you want to remove by running a command that lists users from the MySQL server: SELECT User, Host FROM mysql.user;

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