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How To Use Subqueries in the FROM clause
How To Use Subqueries in the FROM clause? - Oracle DBA FAQ - Understanding SQL SELECT Query Statements If you have a query returning many rows of data, and you want to perform another query on those rows, you can put the first query as a subquery in the FROM clause of the second query. The following... 2007-04-19, 4911👍, 0💬

How To Return Top 5 Rows
How To Return Top 5 Rows? - Oracle DBA FAQ - Understanding SQL SELECT Query Statements If you want the query to return only the first 5 rows, you can use the pseudo column called ROWNUM in the WHERE clause. ROWNUM contains the row number of each returning row from the query. The following statement ... 2007-04-18, 5758👍, 0💬

What Is a Transaction
What Is a Transaction? - Oracle DBA FAQ - Understanding SQL Transaction Management A transaction is a logical unit of work requested by a user to be applied to the database objects. Oracle server introduces the transaction concept to allow users to group one or more SQL statements into a single tran... 2007-04-18, 4983👍, 0💬

How To End the Current Transaction
How To End the Current Transaction? - Oracle DBA FAQ - Understanding SQL Transaction Management There are several ways the current transaction can be ended: Running the COMMIT statement will explicitly end the current transaction. Running the ROLLBACK statement will explicitly end the current transa... 2007-04-18, 4876👍, 0💬

How To Start a New Transaction
How To Start a New Transaction? - Oracle DBA FAQ - Understanding SQL Transaction Management There is no SQL statement to explicitly start a new transaction. Oracle server implicitly starts a new transaction with the following two conditions: The first executable statement of a new user session will ... 2007-04-18, 5015👍, 0💬

How To Commit the Current Transaction
How To Commit the Current Transaction? - Oracle DBA FAQ - Understanding SQL Transaction Management If you have used some DML statements updated some data objects, and you want to have the updates to be permanently recorded in the database, you can use the COMMIT statement. It will make all the datab... 2007-04-18, 4976👍, 0💬

How To Create a Testing Table
How To Create a Testing Table? - Oracle DBA FAQ - Understanding SQL Transaction Management If you want to practice DML statements, you should create a testing table as shown in the script below: >cd (OracleXE home directory) >.\bin\sqlplus /nolog SQL> connect HR/fyicenter Connected. SQL> CREATE TABL... 2007-04-18, 5488👍, 0💬

What Happens to the Current Transaction If a DDL Statement Is Executed
What Happens to the Current Transaction If a DDL Statement Is Executed? - Oracle DBA FAQ - Understanding SQL Transaction Management If a DDL statement is executed, the current transaction will be committed and ended. All the database changes made in the current transaction will become permanent. Thi... 2007-04-18, 4986👍, 0💬

How To Rollback the Current Transaction
How To Rollback the Current Transaction? - Oracle DBA FAQ - Understanding SQL Transaction Management If you have used some DML statements updated some data objects, you find a problem with those updates, and you don't want those updates to be permanently recorded in the database, you can use the ROL... 2007-04-18, 5063👍, 0💬

What Happens to the Current Transaction If the Session Is Ended
What Happens to the Current Transaction If the Session Is Ended? - Oracle DBA FAQ - Understanding SQL Transaction Management If a session is ended, the current transaction in that session will be committed and ended. All the database changes made in the current transaction will become permanent. Thi... 2007-04-18, 5073👍, 0💬

What Happens to the Current Transaction If the Session Is Killed
What Happens to the Current Transaction If the Session Is Killed? - Oracle DBA FAQ - Understanding SQL Transaction Management If a session is killed by the DBA, the current transaction in that session will be rolled back and ended. All the database changes made in the current transaction will be rem... 2007-04-18, 5175👍, 0💬

How Does Oracle Handle Read Consistency
How Does Oracle Handle Read Consistency? - Oracle DBA FAQ - Understanding SQL Transaction Management Oracle supports two options for you on how to maintain read consistency: READ WRITE (the default option), also called statement-level read consistency. READ ONLY, also called transaction-level read c... 2007-04-18, 5234👍, 0💬

What Is a READ WRITE Transaction
What Is a READ WRITE Transaction? - Oracle DBA FAQ - Understanding SQL Transaction Management A READ WRITE transaction is a transaction in which the read consistency is set at the statement level. In a READ WRITE transaction, a logical snapshot of the database is created at the beginning of the exec... 2007-04-18, 4974👍, 0💬

How To Set a Transaction To Be READ ONLY
How To Set a Transaction To Be READ ONLY? - Oracle DBA FAQ - Understanding SQL Transaction Management If you want a transaction to be set as READ ONLY, you need to the transaction with the SET TRANSACTION READ ONLY statement. Note that a DML statement will start the transaction automatically. So you... 2007-04-17, 5336👍, 0💬

What Is a READ ONLY Transaction
What Is a READ ONLY Transaction? - Oracle DBA FAQ - Understanding SQL Transaction Management A READ ONLY transaction is a transaction in which the read consistency is set at the transaction level. In a READ ONLY transaction, a logical snapshot of the database is created at the beginning of the trans... 2007-04-17, 5086👍, 0💬

What Are the Restrictions in a READ ONLY Transaction
What Are the Restrictions in a READ ONLY Transaction? - Oracle DBA FAQ - Understanding SQL Transaction Management There are lots of restrictions in a READ ONLY transaction: You can not switch to READ WRITE mode. You can not run any INSERT, UPDATE, DELETE statements. You can run SELECT query statemen... 2007-04-17, 5346👍, 0💬

What Are the General Rules on Data Consistency
What Are the General Rules on Data Consistency? - Oracle DBA FAQ - Understanding SQL Transaction Management All SQL statements always work with a snapshot of the database to provide data consistency. For READ WRITE transactions, the snapshot is taken when each statement starts. For READ ONLY transac... 2007-04-17, 5370👍, 0💬

What Are Transaction Isolation Levels Supported by Oracle
What Are Transaction Isolation Levels Supported by Oracle? - Oracle DBA FAQ - Understanding SQL Transaction Management Oracle supports two transaction isolation levels: READ COMMITTED (the default option). If the transaction contains DML that requires row locks held by another transaction, then the ... 2007-04-17, 6417👍, 0💬

What Is a Data Lock
What Is a Data Lock? - Oracle DBA FAQ - Understanding SQL Transaction Management A data lock is logical flag the Oracle server is placed on data objects to give an exclusive right to a transaction. Statements in other transactions needs to respect data locks based on certain rules. Rules on data loc... 2007-04-17, 5204👍, 0💬

How To Experiment a Data Lock
How To Experiment a Data Lock? - Oracle DBA FAQ - Understanding SQL Transaction Management If you want to have some experience with data locks, you can create two windows runing two SQL*Plus sessions. In session 1, you can run a UPDATE statements to create a data lock. Before committing session 2, s... 2007-04-17, 5078👍, 0💬

How Data Locks Are Respected
How Data Locks Are Respected? - Oracle DBA FAQ - Understanding SQL Transaction Management Here are the rules on how data locks are respected: All statements ignore data locks owned its own transaction. SELECT query statements ignores data locks owned by any transactions. INSERT, UPDATE, and DELETE s... 2007-04-17, 5203👍, 0💬

How To View Existing Locks on the Database
How To View Existing Locks on the Database? - Oracle DBA FAQ - Understanding SQL Transaction Management As can see from the pervious tutorial exercise, performance of the second session is greatly affected by the data lock created on the database. To maintain a good performance level for all session... 2007-04-17, 6635👍, 0💬

How To Create Tables for ODBC Connection Testing
How To Create Tables for ODBC Connection Testing? - Oracle DBA FAQ - ODBC Drivers, DSN Configuration and ASP Connection If you want to follow the tutorial exercises in the sections below, you need to create a user account and a table for ODBC connection testing as shown here: SQL> CONNECT system/ret... 2007-04-17, 5505👍, 0💬

How To Find Out What Oracle ODBC Drivers Are Installed
How To Find Out What Oracle ODBC Drivers Are Installed? - Oracle DBA FAQ - ODBC Drivers, DSN Configuration and ASP Connection To find out what Oracle ODBC drivers are installed on your Windows system, you can use the ODBC manager to look at them: Go to Control Panel. Go to Administrative Tools. Run ... 2007-04-17, 5598👍, 0💬

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.NET C C++ CSS DBA General HTML Java JavaScript JSP JUnit MySQL Networking Oracle Perl Perl PHP PL/SQL RSS Software QA SQL Server Struts Unix Windows XHTML XML