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Transaction Control
The Oracle is transaction oriented; that is, Oracle uses the transactions to make sure the data integrity. The transaction is a sequence of SQL data manipulation statements that does a logical unit of work. For illustration, the two UPDATE statements might credit one bank account and debit another.
At the same time, the Oracle makes permanent or undoes all the database changes made by a transaction. If your program fails in the middle of the transaction, the Oracle detects the error and rolls back the transaction. Therefore, the database is restored to its previous state automatically.
You use the ROLLBACK, COMMIT, SAVEPOINT, & SET TRANSACTION commands to control the transactions. The COMMIT makes everlasting and any database changes made during the present transaction. The ROLLBACK ends the present transaction and undoes any changes made as the transaction began. The SAVEPOINT marks the present point in the processing of a transaction. Used with the ROLLBACK, SAVEPOINT undoes part of a transaction. The SET TRANSACTION sets the transaction properties like the read/write access and isolation level.
OPEN-FOR Statement The OPEN-FOR statements execute the multi-row query related with a cursor variable. It also allocates the resources used by the Oracle to process the query a
Control Structures The Control structures are the most important PL/SQL extension to the SQL. Not only does PL/SQL let you manipulate Oracle data, it lets you process the data
FOR-LOOP While the number of iterations through a WHILE loop is unknown till the loop completes, then the number of iterations through a FOR loop is known before the loop is ent
Example of ADD CONSTRAINT in SQL Example: Alternative formulation for MAX_ENROLMENTS ALTER TABLE IS_ENROLLED_ON ADD CONSTRAINT MAX_ENROLMENTS CHECK ((SELECT COUNT (*)
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Cursor Attributes The Cursors and cursor variables have 4 attributes which give you helpful information about the execution of a data manipulation statement. Syntax:
Assignment Source Not a Literal - Variable Syntax: SET SN = SID (SUBSTRING (SN.C FROM 1 FOR 1)||'5');
At times, customers make mistakes in submitting their orders and call to cancel the order. Brewbean’s wants to create a trigger that automatically updates the stock level of all pr
Use the MASCOT tables CREDITRS, PORDS and PAYMENTS to write SQL queries to solve the following business problems. These tables / data are available to you via the USQ Oracle server
Second Step at defining type SID in SQL CREATE TYPE SID AS VARCHAR(5) ; Explanation: TYPE SID announces that a type named SID is being defined to the system.
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