1. Ch 7 Introduction to SQL

2. Learning Objectives The basic commands and functions of SQL How to use SQL for data administration (to create tables, indexes, and views) How to use SQL for data manipulation (to add, modify, delete, and retrieve data) How to use SQL to query a database to extract useful information

3. SQL --a standard for relational DB --used as DDL, DML --portable Benefits:.reduced training costs.enhanced productivity.application portability.multiple vendors.application longevity.cross systems communications

4. CREATE TABLEs:..SEE Pg 223 [RC]; ORACLE HANDOUT; and lesson 17 (BF) define fields field type length null/not null unique primary key foreign key

5. Create Statement Format: CREATE TABLE tablename (col name datatype col_constraints,. [primary key block] [referential constraint]..);

6. constraints in Create table statements Constraint clause can constrain a single column or a group of columns in a table It helps maintain data integrity –Primary key –Foreign key –Check conditions

7. Two ways to specify constraints part of col def –(col constraint) at the end of the table –(table constraint)

8. Primary key A table can have only ONE primary key P.K. can not have NULL values for single-column primary key, it can be defined with a column For composite it must be defined as a constraint

9. WORKER (w-name, age, lodging) Create table WORKER (w_name varchar(25) Primary key, age number, Lodging varchar(15)); or Create table WORKER ( w_name varchar(25), age number, Lodging varchar(15), primary key (name));

10. ENROLL(st_name, cl_name, grade) PK is st_name, cl_name Create table Enrollment (ST_name varchar(30) not null, cl_name varchar(25) not null, grade smallint primary key (st_name, cl_name)); NOTE: A concatenated (composite) PK must be defined at the END

11. Foreign Key: (SEE ORACLE HANDOUT AND PAGE 241 (RC), LESSON 22 (bf) known as referential integrity constraint ex: WORKER (name, age, lodging) LODGING (lodging_name, No_of_rooms, lodging_Address)

12. Create table WORKER (name... age... lodging..REFERENCES LODGING); will automatically reference PK of LODGING relation or foreign key(lodging) references LODGING(lodging_name)

13. CHECK constraint: lesson 22 (bf);227(RC) format: col type CHECK (condition) condition is any valid expression that tests True/false. ex: if age should be between 18 & 65 Create table WORKER (name.. agenumber check (age between 18 and 65), lodging...); or age...check (age > 12), ex: class char(20) not null check (lower(class) in ('so', 'jr', 'sp') )

14. Data type (see ORACLE handout) CHAR(size) May contain any printable character such as 'A', '3', '&', or ' ' (blanks). Maximum size: 255 characters. Default is 1 byte. Padded on right with blanks to full length of size. VARCHAR2(size) Variable length character string having a maximum of size bytes (up to 2000). NOT padded with blanks. NUMBER For a numeric column of up to 40 digits. May be used with or without a size designation. You may use this type for integer fields, or for fields in which you wish to insert the decimal point. NUMBER(size) For a NUMBER column of the specified size. NUMBER(size, d) For a NUMBER column of specified size with d digits after the decimal point. For example, NUMBER(6,2) could contain nothing larger than 9999.99 without generating an error message. DATE The DATE data type is stored in a special internal ORACLE format that includes not just the month, day, and year, but also the hour, minute, and second. However, for most tables, you will not need to be concerned about the time. For inserting a date into a table, use the following format: '10-OCT-06'.

15. ex: ORDER(O#, O_date, Promised_date, C#) CUSTOMER(C#, name, address, discount) CREATE TABLE ORDER (ORDERNO NUMBER NOT NULL, ORDERDATE DATE, PROMISED_DATE DATE, CUSTOMER_NO CHAR925) NOT NULL REFERENCES CUSTOMER, PRIMARY KEY(ORDERNO));

16. Entering Data in tables: lesson 15 (BF), p230(RC) and oracle handout Format: INSERT INTO table-name VALUES ( val1, val2, val3...) values must be in the same order as the cols in the table structure char must be in single quotes date must be in quotes and default format (see ORACLE handout) Ex: ORDER(O#, O_date, Promised_date, C#) Sql>insert into order values (61396,’6-jun-06', '29-jun-06',1256); you can also insert a NULL value in a column..col will be left empty for this row Ex: insert into order values(61396,'6-jun-06',null,1256);

17. SQL SQL can be used to manipulate data (DML) format: Sql>SELECT col name(s) FROM table name(s) [Where condition(s)] [Group BY..][HAVING.] [UNION\INTERSECT\MINUS [ORDER BY....]

18. Assume following tables Customer ( Cust_numb, Cust_name, Cust_address, cust_state,Cust_balance,Credit_limit, sales_numb) Salesperson (Sales_numb, sales_name, Sale_add, sales_state, commission_rate, sales) Order (Order_numb, Order_date, Cust_numb)

19. Working with single table List names and balances of each customer Sql>Select cust_name, cust_balance From Customer; If you want all attributes Sql>select * from customer; * Is a wild card and selects everything

20. Remove duplicate entries Select name of states customers live in Sql>select distinct cust_state From customer;

21. LOGICAL TESTS AGAINST A SINGLE VALUE: Used with-- where clause Creates a horizontal subsection Mathematical operators: =, >, >=, or !=

22. List the name of customer whose customer number is 9833 Sql> select cust_name From customer Where cust_numb = 9833;

23. List the names of salesperson who live in MD Ex: give the customers who ordered before February 15, 2007. Sql>select cust_numb From order where order_date <’15-Feb- 2006’;

24. LOGICAL operators: And Or Not List the names of salespeople who live in new york and earn more than 5% as commission Sql>select sales_name From salesperson Where upper(sales_ad) = ‘NEWYORK’ AND commission_rate is > 5% List the names of salespeople who do not live in new york and earn more than 5% as commission

25. Case Sensitivity test Upper Lower

26. SPECIAL OPERATORS In Between [not] in [not] between Ex: WHERE CITY IN ('CHICAGO','BALTIMORE','TAMPA') WHERE AGE IN (20,21,22) same as upper(city) =’CHICAGO’ OR upper(city) =’BALTIMORE’ OR upper(city )= ‘TAMPA’

27. Renaming columns with Aliases/ Can do arithmetic calculations on numeric attributes useful when doing calculations format: Sql>select colname AS alias from table name where. …. Ex: give commission of salespeople. Sql>select sales_name, sales*commission_rate as commission From salesperson; EX: List the names of customers whose credit is greater than 2000 but less than 10000

28. Calculations +, -, /, *, ^ Order of calculations: Parentheses, ^, * and /, + and -

29. Comparisons Numeric: Based on numeric values Character: Left to right based on collating sequence of the computer Smithson > Smith

30. Special operator Like Used to find patterns Allows you select tuples that have similar characters in strings % Any # of char. - For ONE character List names of customers whose names end with an s SELECT cust_name FROM customer WHERE lower(cust_name) like ‘%s’;

31. Find the names of salesperson that have a ‘c’ followed by an ‘s’ SORTING output from a query can be ordered Must always be the last line of a query ORDER BY colname {asc} {desc} default is ascending Ex: sort all customers by state and descending order of their credit limit Sql>select * From customer Order by cust_state, credit_limit desc;

32. Exists condition Main query Sub query If subquery returns values, then ONLY main query is executed Format Select col(s) From table name Where exists ( sub query);

33. BUILT-IN-FUNCTIONS: Max Min Sum Avg Ex: Select max(credit), cust_name from customer; Has no meaning because ename is an array and max(salary) is a scalar; cannot associate names with max(sal) Can not mix built-in functions with other attributes, exception with groups

34. Count Used to tally number of not-null values Format: Count (*) Count(distinct attributename) Count (all attribute name) count the number of customer in maryland or virginia Sql> select count(*) from customer where upper(cust_state) In (‘MD’, ‘VA’);

35. Find maximum credit limit of customer whose names contain at least one o Select max(credit_limit), cust_num From customer Where upper(cust_name) like ‘%O%’;

36. Group By think of grouping as categorizing: P260(RC), lesson 10(bf) Allows grouping by rows and then calculate statistics on “groups” group by state Will group by state Group by state, city Will group by state first, then by city within state Ex: get the maximum credit limit by state Sql>select credit_limit, cust_state From customer Group by cust_state;

37. Condition on groups: Having clause Having puts a condition on groups Ex: select max credit limit by state where there are atleast two customers Sql>select max(credit_limit), cust_state From customer group by cust_state Having count(*) >=2;

38. Copying Part of table Allows you to break tables in parts Two steps: 1.Create NEW table 2. Use SQL to fill up the data Format: Insert into target_table_name (attribute names) From source_table

39. Second method Create new table and select rows directly from source table in single query Format: Create table target_tablename Select attribute names From source_table;

40. Create table credit for customers 1.Method Create table credit (c_name char(20) primary key, C_limit number (8,2)); Insert into credit (c_name, c_limit) Select cust_name, cust_limit From customer; 2 nd Method: Create table credit as Select cust_name as c_name, cust_limit as c_limit From customer;

41. Altering Table structure (see ORACLE Handout), lesson 17, 247 (RC) all changes in table structure are done thru ALTER command MODIFY allows changing existing column ADD allows adding new fields DROP to delete a column

42. Alter format: ALTER TABLE tablename [ADD (col name..., colname...)] or ALTER TABLE tablename [MODIFY (col name..)] or ALTER TABLE tablename [Drop (col name..)]

43. Rules for ADDition can add a col anytime if not null is not specified can add multiple col at one time can add a NULL column in three steps: –add the col without not null –fill every row –modify col to not null

44. Ex: add a new column soc-sec_no to customer alter table customer add (soc_sec_no char(14)); step2: update table customer set soc_sec_no = ‘123-32-4444”; step 3: alter table customer modify (soc_sec_no not null);

45. Changing column structure Ex: increase credit limit to 6,2 Alter table customer Modify (credit_limit number(6,2));

46. Creating views (p 262); ch 18(BF) User’s view of data Create [or REPLACE VIEW view-name (col name) AS SQL query used if this view already exists

47. Create a view of customers with credit limit of >5000 Create view high_limit as select cust_name from customer where Credit_limit >500;

48. COLUMN NAMES MUST BE specified if..column names are derived..two or more cols have the same name Ex: create a view that keeps track of credit averages Create view c_avg (cust_avg, cust_name) as Select cust_name, avg(credit_limit) From customer Group by cust_name);

49. Drop a view/advantages of views Format: Drop view view_name Advantages of views: provide data independence different users can view data differently provide security