What is the rule of Oracle Parse SQL?

Most database system do a specific job. For example, a simple system might immediate thecustomer for an worker wide range, then upgrade series in the EMP and DEPT platforms. In thissituation, you know the cosmetics of the UPDATE declaration at precompile time. That is, youknow which platforms might be modified, the restrictions described for each desk and line, whichcontent might be modified, and the datatype of each line.

However, some applications must agree to (or build) and procedure a number of SQL statements atrun time. For example, a general-purpose review author must develop different SELECT statementfor the various reviews it produces. In this situation, the statement's cosmetics is unidentified untilrun time. Such statement can, and probably will, change from performance to performance. Theyare appropriately known as dynamic SQL statement.

Unlike fixed SQL statement, dynamic SQL statement are not a part of your resource system.Instead, they are held in personality post feedback to or designed by the system at run time. Theycan be joined interactively or study from information.

Advantages and Drawbacks of Powerful SQL

Host applications that agree to and procedure dynamically described SQL statement are handierthan simply included SQL applications. Powerful SQL statement can be designed interactively withfeedback from customers having little or no understanding of SQL.

For example, your system might simply immediate customers for a search situation to be used in theWHERE stipulation of a SELECT, UPDATE, or DELETE declaration. A more technical systemmight allow customers to choose from choices record SQL functions, table and view names, columnnames, and so on. Thus, dynamic SQL allows you to create extremely versatile applications.

However, some dynamic concerns require complicated development, the use of special informationcomponents, and more playback handling. While you might not find the additional handling time,you might find the development difficult unless you completely understand dynamic SQL ideas andmethods.

When to Use Powerful SQL

In exercise, rule of SQL will come across nearly all your development needs. Use dynamic SQLonly if you need its open-ended versatility. Its use is recommended when one of the following itemsis unidentified at precompile time:

1. Written text of the SQL declaration (commands, conditions, and so on)

2. The range of wide range variables

3. The datatypes of wide range variables

4. Sources to databases things such as content, indices, series, platforms, usernames, andviews

5. Requirements for Powerful SQL Statements

6. To signify an energetic SQL declaration, a personality sequence must contain the writingof a real SQL declaration, but not contain the EXEC SQL stipulation, or the declarationterminator, or any of the following included SQL commands:

• ALLOCATE• CLOSE

• DECLARE

• DESCRIBE

• EXECUTE

• FETCH

• FREE

• GET

• INCLUDE

• OPEN

• PREPARE

• SET

• WHENEVER

In most cases, the personality sequence can contain phony wide range factors. They hold locationsin the SQL declaration for actual wide range factors. Because dummy host variables are justplaceholders, you do not declare them and can name them anything you like.

How Powerful SQL Claims are Processed

Typically, a program encourages the consumer for the writing of an SQL declaration and of thevariety factors used in the statement. Oracle then parses the MySQL declaration to make sure itsatisfies format guidelines.

Next, Oracle holds the variety factors to the SQL declaration. That is, Oracle gets the details of thevariety factors so that it can study or create their principles.

Then Oracle carries out the SQL declaration. That is, Oracle does what the SQL declaration askedfor, such as removing series from a desk.

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