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Lecture 7 Manage Schema Objects Manipulating Data

ORACLE. Lecture 7 Manage Schema Objects Manipulating Data. Objectives. After completing this lesson, you should be able to do the following: Add constraints Create indexes Create indexes using the CREATE TABLE statement Creating function-based indexes

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Lecture 7 Manage Schema Objects Manipulating Data

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  1. ORACLE Lecture 7 Manage Schema ObjectsManipulating Data

  2. Objectives After completing this lesson, you should be able to do the following: • Add constraints • Create indexes • Create indexes using the CREATE TABLE statement • Creating function-based indexes • Drop columns and set column UNUSED • Perform FLASHBACK operations

  3. The ALTER TABLE Statement Use the ALTERTABLE statement to: • Add a new column • Modify an existing column • Define a default value for the new column • Drop a column

  4. The ALTER TABLE Statement Use the ALTER TABLE statement to add, modify, or drop columns. ALTER TABLE table ADD (column datatype [DEFAULT expr] [, column datatype]...); ALTER TABLE table MODIFY (column datatype [DEFAULT expr] [, column datatype]...); ALTER TABLE table DROP (column);

  5. Adding a Column • You use the ADD clause to add columns. • The new column becomes the last column. ALTER TABLE dept80 ADD (job_id VARCHAR2(9)); Table altered. …

  6. Modifying a Column • You can change a column’s data type, size, and default value. ALTER TABLE dept80 MODIFY (last_name VARCHAR2(30)); Table altered.

  7. Dropping a Column Use the DROP COLUMN clause to drop columns you no longer need from the table. ALTER TABLE dept80 DROP COLUMN job_id; Table altered.

  8. The SET UNUSED Option • You use the SET UNUSED option to mark one or more columns as unused. • You use the DROP UNUSED COLUMNS option to remove the columns that are marked as unused. ALTER TABLE <table_name> SET UNUSED(<column_name>); ALTER TABLE <table_name> SET UNUSED COLUMN <column_name>; OR ALTER TABLE <table_name> DROP UNUSED COLUMNS;

  9. Adding a Constraint Syntax Use the ALTER TABLE statement to: • Add or drop a constraint, but not modify its structure • Enable or disable constraints • Add a NOT NULL constraint by using the MODIFY clause ALTER TABLE <table_name> ADD [CONSTRAINT <constraint_name>] type (<column_name>);

  10. Adding a Constraint Add a FOREIGN KEY constraint to the EMP2 table indicating that a manager must already exist as a valid employee in the EMP2 table. ALTER TABLE emp2 modify employee_id Primary Key; Table altered. ALTER TABLE emp2 ADD CONSTRAINT emp_mgr_fk FOREIGN KEY(manager_id) REFERENCES emp2(employee_id); Table altered.

  11. ON DELETE CASCADE Delete child rows when a parent key is deleted. ALTER TABLE Emp2 ADD CONSTRAINT emp_dt_fk FOREIGN KEY (Department_id) REFERENCES departments ON DELETE CASCADE); Table altered.

  12. Dropping a Constraint • Remove the manager constraint from the EMP2 table. • Remove the PRIMARY KEY constraint on the DEPT2 table and drop the associated FOREIGN KEY constraint on the EMP2.DEPARTMENT_ID column. ALTER TABLE emp2 DROP CONSTRAINT emp_mgr_fk; Table altered. ALTER TABLE dept2 DROP PRIMARY KEY CASCADE; Table altered.

  13. Disabling Constraints • Execute the DISABLE clause of the ALTERTABLE statement to deactivate an integrity constraint. • Apply the CASCADE option to disable dependent integrity constraints. ALTER TABLE emp2 DISABLE CONSTRAINT emp_dt_fk; Table altered.

  14. Enabling Constraints • Activate an integrity constraint currently disabled in the table definition by using the ENABLE clause. • A UNIQUE index is automatically created if you enable a UNIQUE key or PRIMARY KEY constraint. ALTER TABLE emp2 ENABLE CONSTRAINT emp_dt_fk; Table altered.

  15. Cascading Constraints • The CASCADE CONSTRAINTS clause is used along with the DROP COLUMN clause. • The CASCADE CONSTRAINTS clause drops all referential integrity constraints that refer to the primary and unique keys defined on the dropped columns. • The CASCADE CONSTRAINTS clause also drops all multicolumn constraints defined on the dropped columns.

  16. Cascading Constraints Example: ALTER TABLE emp2 DROP COLUMN employee_id CASCADE CONSTRAINTS; Table altered. ALTER TABLE test1 DROP (pk, fk, col1) CASCADE CONSTRAINTS; Table altered.

  17. Overview of Indexes Indexes are created: • Automatically • PRIMARY KEY creation • UNIQUE KEY creation • Manually • CREATE INDEX statement • CREATE TABLE statement

  18. CREATEINDEX with CREATETABLE Statement CREATE TABLE NEW_EMP (employee_id NUMBER(6) PRIMARY KEY USING INDEX (CREATE INDEX emp_id_idx ON NEW_EMP(employee_id)), first_name VARCHAR2(20),last_name VARCHAR2(25)); Table created. SELECT INDEX_NAME, TABLE_NAME FROM USER_INDEXESWHERE TABLE_NAME = 'NEW_EMP';

  19. Function-Based Indexes • A function-based index is based on expressions. • The index expression is built from table columns, constants, SQL functions, and user-defined functions. CREATE INDEX upper_dept_name_idx ON dept2(UPPER(department_name)); Index created. SELECT * FROM dept2 WHERE UPPER(department_name) = 'SALES';

  20. Removing an Index • Remove an index from the data dictionary by using the DROP INDEX command. • Remove the UPPER_DEPT_NAME_IDX index from the data dictionary. • To drop an index, you must be the owner of the index or have the DROP ANY INDEX privilege. DROP INDEX index; DROP INDEX upper_dept_name_idx; Index dropped.

  21. DROP TABLE …PURGE DROP TABLE dept80 PURGE;

  22. The FLASHBACK TABLE Statement • Repair tool for accidental table modifications • Restores a table to an earlier point in time • Benefits: Ease of use, availability, fast execution • Performed in place • Syntax: FLASHBACK TABLE[schema.]table[,[ schema.]table ]... TO { TIMESTAMP | SCN } expr [ { ENABLE | DISABLE } TRIGGERS ];

  23. The FLASHBACK TABLE Statement DROP TABLE emp2; Table dropped SELECT original_name, operation, droptime, FROM recyclebin; … FLASHBACK TABLE emp2 TO BEFORE DROP; Flashback complete

  24. Summary In this lesson, you should have learned how to: • Add constraints • Create indexes • Create a primary key constraint using an index • Create indexes using the CREATE TABLE statement • Creating function-based indexes • Drop columns and set column UNUSED • Perform FLASHBACK operations

  25. Manipulating Data

  26. Objectives • After completing this lesson, you should be able to do the following: • Describe each data manipulation language (DML) statement • Insert rows into a table • Update rows in a table • Delete rows from a table • Control transactions

  27. Data Manipulation Language • A DML statement is executed when you: • Add new rows to a table • Modify existing rows in a table • Remove existing rows from a table • A transaction consists of a collection of DML statements that form a logical unit of work.

  28. Adding a New Row to a Table New row DEPARTMENTS Insert new rowinto theDEPARTMENTStable

  29. INSERT Statement Syntax • Add new rows to a table by using the INSERT statement: • With this syntax, only one row is inserted at a time. INSERT INTO table [(column [, column...])] VALUES (value [, value...]);

  30. Inserting New Rows • Insert a new row containing values for each column. • List values in the default order of the columns in the table. • Optionally, list the columns in the INSERT clause. • Enclose character and date values in single quotation marks. INSERT INTO departments(department_id, department_name, manager_id, location_id) VALUES (70, 'Public Relations', 100, 1700); 1 row created.

  31. Inserting Rows with Null Values • Implicit method: Omit the column from the column list. INSERT INTO departments (department_id, department_name ) VALUES (30, 'Purchasing'); 1 row created. • Explicit method: Specify the NULL keyword in the VALUES clause. INSERT INTO departments VALUES (100, 'Finance', NULL, NULL); 1 row created.

  32. Inserting Special Values • The SYSDATE function records the current date and time. INSERT 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); 1 row created.

  33. Inserting Specific Date Values • Add a new employee. • Verify your addition. INSERT INTO employees VALUES (114, 'Den', 'Raphealy', 'DRAPHEAL', '515.127.4561', TO_DATE('FEB 3, 1999', 'MON DD, YYYY'), 'AC_ACCOUNT', 11000, NULL, 100, 30); 1 row created.

  34. Creating a Script • Use & substitution in a SQL statement to prompt for values. • & is a placeholder for the variable value. INSERT INTO departments (department_id, department_name, location_id) VALUES (&department_id, '&department_name',&location); 1 row created.

  35. Copying Rows from Another Table • Write your INSERT statement with a subquery: • Do not use the VALUES clause. • Match the number 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%'; 4 rows created.

  36. Changing Data in a Table EMPLOYEES Update rows in the EMPLOYEES table:

  37. UPDATE Statement Syntax • Modify existing rows with the UPDATE statement: • Update more than one row at a time (if required). UPDATE table SET column = value [, column = value, ...] [WHERE condition];

  38. Updating Rows in a Table • 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: UPDATE employees SET department_id = 70 WHERE employee_id = 113; 1 row updated. UPDATE copy_emp SET department_id = 110; 22 rows updated.

  39. Updating Two Columns with a Subquery • Update employee 114’s job and salary to match that of employee 205. UPDATE employees SET job_id = (SELECT job_id FROM employees WHERE employee_id = 205), salary = (SELECT salary FROM employees WHERE employee_id = 205) WHERE employee_id = 114; 1 row updated.

  40. Updating Rows Based on Another Table • Use subqueries in UPDATE statements to update rows in a table based on values from another table: UPDATE copy_emp SET department_id = (SELECT department_id FROM employees WHERE employee_id = 100) WHERE job_id = (SELECT job_id FROM employees WHERE employee_id = 200); 1 row updated.

  41. Removing a Row from a Table DEPARTMENTS Delete a row from the DEPARTMENTS table:

  42. DELETE Statement • You can remove existing rows from a table by using the DELETE statement: DELETE [FROM] table [WHERE condition];

  43. Deleting Rows from a Table • Specific rows are deleted if you specify the WHERE clause: • All rows in the table are deleted if you omit the WHERE clause: DELETE FROM departments WHERE department_name = 'Finance'; 1 row deleted. DELETE FROM copy_emp; 22 rows deleted.

  44. Deleting Rows Based on Another Table • Use subqueries in DELETE statements to remove rows from a table based on values from another table: DELETE FROM employees WHERE department_id = (SELECT department_id FROM departments WHERE department_name LIKE '%Public%'); 1 row deleted.

  45. SELECT INSERT UPDATE DELETE MERGE CREATE ALTER DROP RENAME TRUNCATE COMMENT COMMIT ROLLBACK SAVEPOINT GRANT REVOKE SQL Statements Data manipulation language (DML) Data definition language (DDL) Transaction control Data control language (DCL)

  46. TRUNCATE Statement • Removes all rows from a table, leaving the table empty and the table structure intact • Is a data definition language (DDL) statement rather than a DML statement; cannot easily be undone • Syntax: • Example: TRUNCATE TABLE table_name; TRUNCATE TABLE copy_emp;

  47. INSERT INTO (SELECT employee_id, last_name, email, hire_date, job_id, salary, department_id FROM employees WHERE department_id = 50) VALUES (99999, 'Taylor', 'DTAYLOR', TO_DATE('07-JUN-99', 'DD-MON-RR'), 'ST_CLERK', 5000, 50); 1 row created. Using a Subquery in an INSERT Statement

  48. Using a Subquery in an INSERT Statement • Verify the results: SELECT employee_id, last_name, email, hire_date, job_id, salary, department_id FROM employees WHERE department_id = 50;

  49. Database Transactions • A database transaction consists of one of the following: • DML statements that constitute one consistent change to the data • One DDL statement • One data control language (DCL) statement

  50. Database Transactions • Begin when the first DML SQL statement is executed • End with one of the following events: • A COMMIT or ROLLBACK statement is issued. • A DDL or DCL statement executes (automatic commit). • The user exits iSQL*Plus. • The system crashes.

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