This document provides an overview of data manipulation language (DML) statements and transaction control in Oracle databases. It describes how to insert, update, delete rows from tables using DML statements like INSERT, UPDATE, DELETE. It also explains how to use the MERGE statement to conditionally insert or update rows. Additionally, it covers transaction control using statements like COMMIT, ROLLBACK, SAVEPOINT and how they affect the state of data. Read consistency and locking mechanisms implemented in Oracle to avoid conflicts during concurrent data access are also summarized.

1. Manipulating Data

4. Adding a New Row to a Table DEPARTMENTS New row … insert a new row into the DEPARMENTS table…

12. Changing Data in a Table EMPLOYEES Update rows in the EMPLOYEES table.

18. Removing a Row from a Table Delete a row from the DEPARTMENTS table. DEPARTMENTS

31. Merging Rows MERGE INTO copy_emp c USING employees e ON (c.employee_id = e.employee_id) WHEN MATCHED THEN UPDATE SET ... WHEN NOT MATCHED THEN INSERT VALUES...; SELECT * FROM COPY_EMP; no rows selected SELECT * FROM COPY_EMP; 20 rows selected.

35. Controlling Transactions ROLLBACK to SAVEPOINT B ROLLBACK to SAVEPOINT A ROLLBACK SAVEPOINT B SAVEPOINT A DELETE INSERT UPDATE INSERT COMMIT Time Transaction

44. Implementation of Read Consistency SELECT * FROM userA.employees; UPDATE employees SET salary = 7000 WHERE last_name = 'Goyal'; Data blocks Rollback segments changed and unchanged data before change “old” data User A User B Read consistent image

47. Summary Description Adds a new row to the table Modifies existing rows in the table Removes existing rows from the table Conditionally inserts or updates data in a table Makes all pending changes permanent Is used to rollback to the savepoint marker Discards all pending data changes Statement INSERT UPDATE DELETE MERGE COMMIT SAVEPOINT ROLLBACK In this lesson, you should have learned how to use DML statements and control transactions.

53. Read Consistency Example Output Time Session 1 Session 2 t1 t2 t3 t4 t5 SELECT salary FROM employees WHERE last_name='King'; 24000 UPDATE employees SET salary=salary+10000 WHERE last_name='King'; 24000 COMMIT; 34000 SELECT salary FROM employees WHERE last_name='King'; SELECT salary FROM employees WHERE last_name='King';