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Agenda for Class 2/02/2006

Agenda for Class 2/02/2006. Finish discussing constraints generated with the CREATE TABLE statement. Discuss DROP statement. Discuss INSERT, COMMIT, DELETE, and UPDATE statements. Introduce SELECT statement. Discuss a few helpful SQLPlus commands. Do SQL class exercise.

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Agenda for Class 2/02/2006

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  1. Agenda for Class 2/02/2006 • Finish discussing constraints generated with the CREATE TABLE statement. • Discuss DROP statement. • Discuss INSERT, COMMIT, DELETE, and UPDATE statements. • Introduce SELECT statement. • Discuss a few helpful SQLPlus commands. • Do SQL class exercise.

  2. Example 1: Simple Order Database discussed in class on Tuesday: We discussed in class how to create the tables with primary key and referential integrity constraints, now let’s add some other constraints.

  3. CREATE TABLE ord (order_no NUMBER(5), order_date DATE, customer_no NUMBER(3) NOT NULL, ship_code CHAR(2) CHECK (ship_code in(‘02’,’A1’,’B3’,’04’)), CONSTRAINT ord_pk PRIMARY KEY (order_no)); CREATE TABLE prod (prod_no NUMBER(3), description VARCHAR2(50), cost NUMBER(8,2) CHECK (cost > .02), CONSTRAINT prod_pk PRIMARY KEY (prod_no)); CREATE TABLE prod_on_ord (order_no NUMBER(5), prod_no NUMBER(3), quantity NUMBER(6,2) DEFAULT 1, price NUMBER(8,2), CONSTRAINT prodord_pk PRIMARY KEY (order_no, prod_no), CONSTRAINT ord_fk FOREIGN KEY(order_no) REFERENCES ord(order_no), CONSTRAINT prod_fk FOREIGN KEY(prod_no) REFERENCES prod(prod_no));

  4. What is a recursive referential integrity constraint? • Imagine a situation where a company is a parent company of another company. The organization as a whole keeps track of company name, phone and the identifier of the parent company. CompanyID Name Phone ParentCompanyID 123 Dining Supply Co 858-133-4551 null 177 DineOut 775-677-6771 123 897 RestCo 805-891-1233 123 788 Jansen Supply 503-281-0667 897

  5. Creating a recursive referential integrity constraint CREATE TABLE company (companyID CHAR(3), companyname VARCHAR2(40), phone CHAR(10), parentcompanyID CHAR(3), CONSTRAINT company_pk PRIMARY KEY (companyID), CONSTRAINT parent_fk FOREIGN KEY (parentcompanyID) REFERENCES company(companyID));

  6. Deleting a table • Cannot have more than one data object with the same name. • Must delete data objects before re-creating them. • SQL Statement is: DROP TABLE prod_on_ord; • Must delete objects in the order of referential integrity constraints, unless the constraints are “cascaded” during the delete process. • SQL Statement is: DROP TABLE prod_on_ord CASCADE CONSTRAINTS;

  7. SQL INSERT Statement • Used to “populate” a table with data. • Used to enter one row of data. • Character/string data must be entered surrounded by single quotes. • Dates are best entered using the Oracle default format of dd-mon-yy or dd-mon-yyyy. For example, today’s date in the Oracle default format is: 02-feb-2006

  8. Using the original ord table example, these are sample INSERT statements used to add rows to the table INSERT INTO ord VALUES (14452, ’02-feb-06’, 234, ‘A1’); INSERT INTO ord VALUES (23415, SYSDATE, 2100, ‘B3’); INSERT INTO ord VALUES (14419, ’08-jul-1999’, 320, ‘02’); INSERT INTO ord (order_no, customer_no) VALUES (2231, 334); COMMIT;

  9. Purpose of the COMMIT Statement • Some SQL statements act directly to save results on disk, others do not. • CREATE produces a data object on disk; not just in main memory. • INSERT adds a row of data in main memory. • To save data from memory to disk, use the COMMIT statement.

  10. Deleting Data from a Table DELETE FROM ord WHERE ord_no = 3344; DELETE FROM prod WHERE cost < 1.56; DELETE FROM prod_on_ord WHERE price < 1.25 AND quantity < 3;

  11. Changing Existing Data in a Table UPDATE ord SET order_date = ’22-jan-06’ WHERE order_no = 14452; UPDATE ord SET order_date = SYSDATE WHERE order_no = 14452; UPDATE prod SET cost = 0 WHERE description = ‘bolt’;

  12. Retrieving Data from a Table General Syntax for accessing data from a table SELECT [all or distinct] (what columns) FROM (table) WHERE (condition) GROUP BY (grouping fields) HAVING (condition) ORDER BY (sort fields)

  13. Example of Retrieving Data from a Table SELECT * FROM ord; SELECT * FROM prod’ SELECT order_id, order_date FROM ord; SELECT order_id, order_date FROM ord WHERE cust_id = ‘6511’; The * means retrieve all columns. The FROM statement, without a WHERE statement, means retrieve all rows.

  14. Retrieving Info from Oracle SQLPlus command to see structure of data object: DESCRIBE emp; SQL command to see contents of your tablespace: SELECT table_name FROM tabs; Tabs is a data view in the Oracle data dictionary containing information about all database objects in a given tablespace.

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