数据库技术与Oracle：sql-08 Manipulating Data

1、8Copyright Oracle Corporation, 2001. All rights reserved.Manipulating Data8-2ObjectivesAfter completing this lesson, you should be able to do the following:Describe each DML statementInsert rows into a tableUpdate rows in a tableDelete rows from a tableMerge rows in a tableControl transactions8-3Dat

2、a Manipulation LanguageA DML statement is executed when you:Add new rows to a tableModify existing rows in a tableRemove existing rows from a tableA transaction consists of a collection of DML statements that form a logical unit of work.8-4Adding a New Row to a TableDEPARTMENTS New rowinsert a new r

3、ow into the DEPARMENTS table8-5The INSERT Statement SyntaxAdd new rows to a table by using the INSERT statement.Only one row is inserted at a time with this syntax.INSERT INTOtable (column , column.)VALUES(value , value.);8-6Inserting New RowsInsert a new row containing values for each column.List v

4、alues in the default order of the columns in the table. Optionally, list the columns in the INSERT clause.Enclose character and date values within single quotation marks.INSERT INTO departments(department_id, department_name, manager_id, location_id)VALUES (70, Public Relations, 100, 1700);1 row cre

5、ated.8-7INSERT INTOdepartmentsVALUES(100, Finance, NULL, NULL);INSERT INTOdepartments (department_id, department_name )VALUES(30, Purchasing);Inserting Rows With Null ValuesImplicit method: Omit the column from the column list.Explicit method: Specify the NULL keyword in the VALUES clause.8-8INSERT

6、INTO employees (employee_id, first_name, last_name, email, phone_number, hire_date, job_id, salary, commission_pct, manager_id, department_id)VALUES (113, Louis, Popp, LPOPP, 515.124.4567, SYSDATE, AC_ACCOUNT, 6900, NULL, 205, 100);Inserting Special ValuesThe SYSDATE function records the current dat

7、e and time.8-9INSERT INTO employeesVALUES (114, Den, Raphealy, DRAPHEAL, 515.127.4561, TO_DATE(FEB 3, 1999, MON DD, YYYY), AC_ACCOUNT, 11000, NULL, 100, 30);Inserting Specific Date ValuesAdd a new employee.Verify your addition.8-10Write your INSERT statement with a subquery.Do not use the VALUES cla

8、use.Match the number and data type of columns in the INSERT clause to those in the subquery.INSERT INTO sales_reps(id, name, salary, commission_pct) SELECT employee_id, last_name, salary, commission_pct FROM employees WHERE job_id LIKE %REP%;Copying Rows From Another Table8-11Changing Data in a Tabl

9、eEMPLOYEESUpdate rows in the EMPLOYEES table.8-12The UPDATE Statement SyntaxModify existing rows with the UPDATE statement.Update more than one row at a time, if required.UPDATEtableSETcolumn = value , column = value, .WHERE condition;8-13UPDATE employeesSET department_id = 70WHERE employee_id = 113

10、;Specific row or rows are modified if you specify the WHERE clause.All rows in the table are modified if you omit the WHERE clause.Updating Rows in a TableUPDATE copy_empSET department_id = 110;8-14UPDATE employeesSET job_id = (SELECT job_id FROM employees WHERE employee_id = 205), salary = (SELECT

11、salary FROM employees WHERE employee_id = 205) WHERE employee_id = 114;Updating Two Columns With a SubqueryUpdate employee 114s job and salary to match that of employee 205.8-15UPDATE copy_empSET department_id = (SELECT department_id FROM employees WHERE employee_id = 100)WHERE job_id = (SELECT job_

12、id FROM employees WHERE employee_id = 200);Updating Rows Based on Another TableUse subqueries in UPDATE statements to update rows in a table based on values from another table.8-16Delete a row from the DEPARTMENTS table.Removing Rows From a Table DEPARTMENTS 8-17The DELETE StatementYou can remove ex

13、isting rows from a table by using the DELETE statement.DELETE FROM tableWHERE condition;8-18Specific rows are deleted if you specify the WHERE clause.All rows in the table are deleted if you omit the WHERE clause.Deleting Rows From a Table DELETE FROM departments WHERE department_name = Finance;DELE

14、TE FROM copy_emp;8-19DELETE FROM employeesWHERE department_id = (SELECT department_id FROM departments WHERE department_name LIKE %Public%);Deleting Rows Based on Another TableUse subqueries in DELETE statements to remove rows from a table based on values from another table.8-20Overview of the Expli

15、cit Default FeatureWith the explicit default feature, you can use the DEFAULT keyword as a column value where the column default is desired.The addition of this feature is for compliance with the SQL: 1999 Standard.This allows the user to control where and when the default value should be applied to

16、 data.Explicit defaults can be used in INSERT and UPDATE statements.8-21Using Explicit Default ValuesINSERT INTO departments (department_id, department_name, manager_id) VALUES (300, Engineering, DEFAULT);UPDATE departments SET manager_id = DEFAULT WHERE department_id = 10;DEFAULT with INSERT:DEFAUL

17、T with UPDATE:8-22The MERGE StatementProvides the ability to conditionally update or insert data into a database tablePerforms an UPDATE if the row exists, and an INSERT if it is a new row:Avoids separate updatesIncreases performance and ease of useIs useful in data warehousing applications8-23The M

18、ERGE Statement SyntaxYou can conditionally insert or update rows in a table by using the MERGE statement.MERGE INTO table_name table_alias USING (table|view|sub_query) alias ON (join condition) WHEN MATCHED THEN UPDATE SET col1 = col_val1, col2 = col2_val WHEN NOT MATCHED THEN INSERT (column_list) V

19、ALUES (column_values);8-24MERGE INTO copy_emp c USING employees e ON (c.employee_id = e.employee_id)WHEN MATCHED THEN UPDATE SET c.first_name = e.first_name, c.last_name = e.last_name, . c.department_id = e.department_idWHEN NOT MATCHED THEN INSERT VALUES(e.employee_id, e.first_name, e.last_name, e.

20、email, e.phone_number, e.hire_date, e.job_id, e.salary, mission_pct, e.manager_id, e.department_id);Merging RowsInsert or update rows in the COPY_EMP table to match the EMPLOYEES table.8-25Merging RowsMERGE INTO copy_emp c USING employees e ON (c.employee_id = e.employee_id)WHEN MATCHED THEN UPDATE

21、SET .WHEN NOT MATCHED THEN INSERT VALUES.;SELECT * FROM COPY_EMP;no rows selectedSELECT * FROM COPY_EMP;20 rows selected.8-26Database TransactionsA database transaction consists of one of the following:DML statements which constitute one consistent change to the dataOne DDL statementOne DCL statemen

22、t8-27Database TransactionsBegin when the first DML SQL statement is executedEnd with one of the following events:A COMMIT or ROLLBACK statement is issuedA DDL or DCL statement executes (automatic commit)The session endThe system crashes8-28Advantages of COMMIT and ROLLBACK StatementsWith COMMIT and

23、ROLLBACK statements, you can: Ensure data consistencyPreview data changes before making changes permanentGroup logically related operations8-29Controlling TransactionsSAVEPOINT BSAVEPOINT ADELETEINSERTUPDATEINSERTCOMMITTimeTransactionROLLBACK to SAVEPOINT BROLLBACK to SAVEPOINT AROLLBACK8-30UPDATE.S

24、AVEPOINT update_done;INSERT.ROLLBACK TO update_done;Rolling Back Changes to a MarkerCreate a marker in a current transaction by using the SAVEPOINT statement.Roll back to that marker by using the ROLLBACK TO SAVEPOINT statement.8-31An automatic commit occurs under the following circumstances:DDL sta

25、tement is issuedDCL statement is issuedNormal exit from iSQL*Plus, without explicitly issuing COMMIT or ROLLBACK statementsAn automatic rollback occurs under an abnormal termination of iSQL*Plus or a system failure.Implicit Transaction Processing8-32State of the Data Before COMMIT or ROLLBACKThe pre

26、vious state of the data can be recovered.The current user can review the results of the DML operations by using the SELECT statement.Other users cannot view the results of the DML statements by the current user.The affected rows are locked; other users cannot change the data within the affected rows

27、.8-33State of the Data After COMMITData changes are made permanent in the database.The previous state of the data is permanently lost.All users can view the results.Locks on the affected rows are released; those rows are available for other users to manipulate.All savepoints are erased.8-34COMMIT;Ma

28、ke the changes.Commit the changes.DELETE FROM employeesINSERT INTO departments VALUES (290, Corporate Tax, NULL, 1700);Committing Data8-35State of the Data After ROLLBACKDiscard all pending changes by using the ROLLBACK statement:Data changes are undone.Previous state of the data is restored.Locks o

29、n the affected rows are released.DELETE FROM copy_emp;ROLLBACK;8-36Statement-Level RollbackIf a single DML statement fails during execution, only that statement is rolled back.The Oracle server implements an implicit savepoint.All other changes are retained.The user should terminate transactions exp

30、licitly by executing a COMMIT or ROLLBACK statement.8-37Read ConsistencyRead consistency guarantees a consistent view of the data at all times.Changes made by one user do not conflict with changes made by another user. Read consistency ensures that on the same data:Readers do not wait for writers.Wr

31、iters do not wait for readers.8-38SELECT *FROM userA.employees;Implementation of Read ConsistencyUPDATE employeesSET salary = 7000WHERE last_name = Goyal;DatablocksRollbacksegmentschangedand unchanged databefore change“old” dataUser AUser BReadconsistentimage8-39SELECT salary FROM employeesWHERE last_name=King;24000UPDATE employeesSET salary=salary+10000WHERE last_name=King;24000COMMIT;34000SELECT salary FROM employeesWHERE