What is a database cursor in SQL?
In computer science, a database cursor is a mechanism that enables traversal over the records in a database. … In SQL procedures, a cursor makes it possible to define a result set (a set of data rows) and perform complex logic on a row by row basis.
What is a cursor in database?
A database cursor is an identifier associated with a group of rows. It is, in a sense, a pointer to the current row in a buffer. … Statements that return more than one row of data from the database server: A SELECT statement requires a select cursor. An EXECUTE FUNCTION statement requires a function cursor.
What is the use of cursor in SQL Server?
A SQL Server cursor is a set of T-SQL logic to loop over a predetermined number of rows one at a time. The purpose for the cursor may be to update one row at a time or perform an administrative process such as SQL Server database backups in a sequential manner.
What is cursor in SQL Server with example?
Cursor is a database object to retrieve data from a result set one row at a time, instead of the T-SQL commands that operate on all the rows in the result set at one time. We use a cursor when we need to update records in a database table in singleton fashion means row by row.
What are the types of cursor?
There are 2 types of Cursors: Implicit Cursors, and Explicit Cursors. These are explained as following below. Implicit Cursors: Implicit Cursors are also known as Default Cursors of SQL SERVER.
What is the cursor life cycle?
SQL Cursor Life Cycle
A cursor is declared by defining the SQL statement. A cursor is opened for storing data retrieved from the result set. When a cursor is opened, rows can be fetched from the cursor one by one or in a block to do data manipulation. The cursor should be closed explicitly after data manipulation.
What is cursor example?
Oracle creates a memory area, known as the context area, for processing an SQL statement, which contains all the information needed for processing the statement; for example, the number of rows processed, etc. A cursor is a pointer to this context area. … A cursor holds the rows (one or more) returned by a SQL statement.
What is difference between trigger and cursor?
A cursor is activated and thus created in response to any SQL statement. A trigger is executed in response to a DDL statement, DML statement or any database operation.
Should I use cursor SQL?
Cursors could be used in some applications for serialized operations as shown in example above, but generally they should be avoided because they bring a negative impact on performance, especially when operating on a large sets of data.
Is it good to use cursor in SQL?
SQL Cursors are fine as long as you use the correct options: INSENSITIVE will make a temporary copy of your result set (saving you from having to do this yourself for your pseudo-cursor). READ_ONLY will make sure no locks are held on the underlying result set.
How do you write a trigger?
create trigger [trigger_name]: Creates or replaces an existing trigger with the trigger_name. [before | after]: This specifies when the trigger will be executed. {insert | update | delete}: This specifies the DML operation. on [table_name]: This specifies the name of the table associated with the trigger.
What are the types of cursor in SQL?
SQL Server supports three cursor implementations.
- Transact-SQL cursors. Transact-SQL cursors are based on the DECLARE CURSOR syntax and used mainly in Transact-SQL scripts, stored procedures, and triggers. …
- Application programming interface (API) server cursors. …
- Client cursors. …
- Forward-only. …
- Static. …
- Keyset. …
- Dynamic.
How can I see the cursor in SQL?
Difference between View and Cursor in SQL :
- Declare the cursor in declaration section.
- Open the cursor in execution section.
- Fetch the cursor to retrieve data into PL/SQL variable.
- Close the cursor to release allocated memory.
Why use triggers in SQL?
Because a trigger resides in the database and anyone who has the required privilege can use it, a trigger lets you write a set of SQL statements that multiple applications can use. It lets you avoid redundant code when multiple programs need to perform the same database operation.