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Oracle 20c 概念手册 PDF 下载
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PL/SQL and Java
PL/SQL is a procedural extension to Oracle SQL.
PL/SQL is integrated with Oracle Database, enabling you to use all of the Oracle
Database SQL statements, functions, and data types. You can use PL/SQL to control
the flow of a SQL program, use variables, and write error-handling procedures.
A primary benefit of PL/SQL is the ability to store application logic in the database
itself. A PL/SQL procedure or function is a schema object that consists of a set of SQL
statements and other PL/SQL constructs, grouped together, stored in the database,
and run as a unit to solve a specific problem or to perform a set of related tasks. The
principal benefit of server-side programming is that built-in functionality can be
deployed anywhere.
Oracle Database can also store program units written in Java. A Java stored
procedure is a Java method published to SQL and stored in the database for general
use. You can call existing PL/SQL programs from Java and Java programs from PL/
SQL.
See Also:
• "Server-Side Programming: PL/SQL and Java" • Oracle Database Development Guide to learn more about choosing a
programming environment
Transaction Management
Oracle Database is designed as a multiuser database. The database must ensure that
multiple users can work concurrently without corrupting one another's data.
Transactions
A transaction is a logical, atomic unit of work that contains one or more SQL
statements.
An RDBMS must be able to group SQL statements so that they are either all
committed, which means they are applied to the database, or all rolled back, which
means they are undone.
An illustration of the need for transactions is a funds transfer from a savings account to
a checking account. The transfer consists of the following separate operations:
1. Decrease the savings account.
2. Increase the checking account.
3. Record the transaction in the transaction journal.
Oracle Database guarantees that all three operations succeed or fail as a unit. For
example, if a hardware failure prevents a statement in the transaction from executing,
then the other statements must be rolled back.
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