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What Are Cursor Variables ?
The Cursor variables are like C or Pascal pointers that hold the memory location (address) of some item rather of the item itself. Therefore, declaring a cursor variable creates a pointer, not an item. In the PL/SQL, the pointer has a datatype REF X, where REF is short form for the REFERENCE and X stands for the class of objects. Therefore, a cursor variable has the datatype REF CURSOR.
To execute a multi-row query, the Oracle opens an unnamed work region which stores processing the information. To access the information, you can use an explicit cursor that names the work area. Or, you can use a cursor variable that points to the work region. While the cursor always refers to the similar query work region, a cursor variable can refer to various work regions. Therefore, the cursors and cursor variables are not interoperable.
Operators on Tables and Rows Row Extraction TUPLE FROM r, SQL has row subqueries. These are just like scalar subqueries except that they may specify more than one column.
Example of GROUPBY Operator Example: How many students sat each exam, using GROUP BY, NATURAL LEFT JOIN, and COALESCE SELECT CourseId, COALESCE (n, 0) AS n FROM COURS
Packaging Cursors You can split a cursor specification from its body for placement in a package. In that way, you can change the cursor body without changing the cursor spec
Need for Dynamic SQL: You need dynamic SQL in the situations as follows: 1) You would like to execute a SQL data definition statement (like CREATE), a data control statemen
How Transactions Guard Your Database The transaction is a sequence of SQL data manipulation statements which does a logical unit of work. The Oracle treats the sequence of SQL
LEVEL You use the LEVEL with the SELECT CONNECT BY statement to categorize rows from a database table into a tree structure. The LEVEL returns the level number of a node in a
Perform the following queries on the Hospital1.DB using SQL Anywhere (START EARLY!). a. Which patients have purchased the drug "Tylenol"? List the names and addresses. Arrange the
Anatomy of a Table: Figure shows the terminology used in SQL to refer to parts of the structure of a table. As you can see, SQL has no official terms for its counterpa
Use the RETURNING Clause Frequently, the application requires information about the row affected by a SQL operation, for illustration, to produce a report or take a subsequent
Explicit Cursors The set of rows returned by the query can include zero, one, or multiple rows, depending on how many rows meet your search criteria. Whenever a query returns
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