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.

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.

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));

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. CompanyIDNamePhoneParentCompanyID 123Dining Supply Co null 177DineOut RestCo Jansen Supply

Creating a recursive referential integrity constraint CREATE TABLE company (companyIDCHAR(3), companynameVARCHAR2(40), phoneCHAR(10), parentcompanyIDCHAR(3), CONSTRAINT company_pk PRIMARY KEY (companyID), CONSTRAINT parent_fk FOREIGN KEY (parentcompanyID) REFERENCES company(companyID));

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;

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

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; Using the original ord table example, these are sample INSERT statements used to add rows to the table

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.

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;

Changing Existing Data in a Table UPDATEord SETorder_date = ’22-jan-06’ WHEREorder_no = 14452; UPDATEord SETorder_date = SYSDATE WHEREorder_no = 14452; UPDATEprod SETcost = 0 WHEREdescription = ‘bolt’;

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)

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.

Retrieving Info from Oracle SQLPlus command to see structure of data object: DESCRIBEemp; 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.