1. SQL III

2. Pseudocolumns  Rownum (numeric)  A number for each row in a select query  Example:  Branch(bname, bcity)  SELECT rownum ordered_branch_seq, bname, bcity FROM branch ORDER BY bname;  Rowid (char string)  A character string that represents the physical address for a row of a table.  SELECT rowid, bname, bcity FROM branch.  Access by rowid fastest.  However, rowids may change during some table maintenance operations  Split of table partitions.  If you delete and insert the same branch name, the rowids for that row are likely to be different

3. CONNECT-BY (not in book)  Person (father, name)  Find the children of ‘Mike Johnson’  SELECT a.name FROM Person a where a.father = ‘Mike Johnson’;  What-if you want to find great-great-grandchildren?  Easier way in Oracle: CONNECT-BY  Useful for answering hierarchical queries

4. CONNECT-BY  Find all descendants from Mike Johnson  SELECT a.name FROM Person a START WITH a.name = ‘Mike Johnson’ CONNECT BY PRIOR name = father;  First Level (of recursion)  Mike Johnson  Second Level  All names for which Mike is a father (i.e., children of Mike)  Third Level  All names for which Mike’s children are fathers  ….

5. CONNECT-BY  Find all descendants from Mike Johnson  SELECT a.name FROM Person a START WITH a.name = ‘Mike Johnson’ CONNECT BY PRIOR name = father;  Pseudocolumn: LEVEL SELECT a.name, LEVEL FROM Person a START WITH a.name = ‘Mike Johnson’ CONNECT BY PRIOR name = father;  Ordering among siblings: SELECT a.name, LEVEL FROM Person a START WITH a.name = ‘Mike Johnson’ CONNECT BY PRIOR name = father ORDER SIBLINGS BY name;

6. CONNECT-BY  Find upto grand-children only for Mike Johnson  Restrict the LEVEL to be <=3 (Mike, his children and grand-children)  What if you have “loops” in the data?  Oracle raises an error  To ignore the loops, specify NOCYCLE SELECT a.name, LEVEL FROM Person a START WITH a.name = ‘Mike Johnson’ CONNECT BY NOCYCLE PRIOR name = father ORDER SIBLINGS BY name; Lot more Information: Oracle Help links, or http://www.oracle.com/technology/oramag/webcolumns/2003/techarti cles/gennick_connectby.html http://www.stanford.edu/dept/itss/docs/oracle/10g/server.101/b10759 /queries003.htm

7. SQL Summary Query Language (DML): SELECT, FROM, WHERE GROUP BY, HAVING ORDER BY Nested Queries ( IN, EXISTS, UNIQUE, ALL, SOME, correlation) Aggregates Joins Updates Views PseudoColumns Connect-by hierarchical queries More to come: Inserts, deletes,…. DDL: CREATE TABLE DROP TABLE ALTER TABLE Embedded SQL/JDBC Integrity Constraints Security, authorization

8. SQL: Modification Commands Deletion: DELETE FROM [WHERE ] Example: 1. DELETE FROM account -- deletes all tuples in account 2. DELETE FROM account WHERE bname in (SELECT bname FROM branch WHERE bcity = ‘Bkln’) -- deletes all accounts from Brooklyn branch

9. DELETE  Delete the record of all accounts with balances below the average at the bank. DELETE FROM account WHERE balance < (SELECT AVG(balance) FROM account)  Problem: as we delete tuples from deposit, the average balance changes  Solution used in SQL:  1.First, compute avg balance and find all tuples to delete  2.Next, delete all tuples found above (without recomputing avg or retesting the tuples)

10. SQL: Modification Commands Insertion: INSERT INTO values (..,..,...) or INSERT INTO (att1,.., attn) values(...,...,...) or INSERT INTO Examples: INSERT INTO account VALUES (“Perry”, A-768, 1200) or INSERT INTO account( bname, acct_no, balance) VALUES (“Perry”, A-768, 1200) INSERT INTO account SELECT bname, lno, 200 FROM loan WHERE bname = “Kenmore” gives free $200 savings account for each loan holder at Kenmore

11. SQL: Modification Commands Update: UPDATE SET = WHERE Ex. UPDATE account SET balance = balance * 1.06 WHERE balance > 10000 UPDATE account SET balance = balance * 1.05 WHERE balance <= 10000 Alternative: UPDATE account SET balance = (CASE WHEN balance <= 10000 THEN balance*1.05 ELSE balance*1.06 END)

12. SQL: Modification Commands View Updates: Suppose we have a view: CREATE VIEW branch-loan AS SELECT bname, lno FROM loan And we insert: INSERT INTO branch-loan VALUES( “Perry”, L-308) Then, the system will insert a new tuple ( “Perry”, L-308, NULL) into loan

13. SQL: Modification Commands What about... CREATE VIEW depos-account AS SELECT cname, bname, balance FROM depositor as d, account as a WHERE d.acct_no = a.acct_no INSERT INTO depos-account VALUES( “Smith”, “Perry”, 500) How many relations we need to update? Many systems disallow

14. Built-in Data Types in SQL  date: Dates, containing a (4 digit) year, month and date  Example: date ‘2005-7-27’  time: Time of day, in hours, minutes and seconds.  Example: time ‘09:00:30’ time ‘09:00:30.75’  timestamp: date plus time of day  Example: timestamp ‘2005-7-27 09:00:30.75’  interval: period of time  Example: interval ‘1’ day  Subtracting a date/time/timestamp value from another gives an interval value  Interval values can be added to date/time/timestamp values CREATE TABLE person (name VARCHAR2, age NUMBER); What other data types other than VARCHAR2, NUMBER are allowed?

15. Build-in Data Types in SQL (Cont.)  Can extract values of individual fields from date/time/timestamp  Example: extract (year from r.starttime)  Can cast string types to date/time/timestamp  Example: cast as date  Example: cast as time

16. Other Built-in Special types  Special Types  XMLType (we will see examples at the end of the course)  SDO_GEOMETRY (spatial type) to store 2-d, 3-d geometries  Media Types  ORDImage  ORDAudio  ORDDoc,…

17. User-Defined Types  create type construct in SQL creates user-defined type create type Dollars as numeric (12,2) final  Can create user-defined object types  Name, attributes  Methods (implemeneted in plsql or other external languages)  Example CREATE TYPE geometry as OBJECT ( type varchar2(10), vertex_ordinates number_array);  REF datatypes  Reference to the OID (object identifier) of an object

18. Other Types  VARRAYs  Ordered set of elements  Each element has an index and can be accessed using that.  Example:  CREATE TYPE number_array as VARRAY(100000) of NUMBER;  VARRAY can be:  The datatype of a column in a table  CREATE TABLE properties ( name varchar2(32), geom NUMBER_ARRAY);  Attribute of an object  PL/SQL variable, parameter, or return type  Query: cast it using the TABLE keyword to a table  SELECT * from TABLE( select geom from properties where name=‘CityHall’));

19. Nested Tables  Nested Table (compared to VARRAY)  An unordered set of elements  CREATE OR REPLACE TYPE NumberTab AS TABLE OF Number; /  CREATE TABLE properties ( name VARCHAR2(20), property_geometry NumberTab) NESTED TABLE property_geometry STORE AS geomtab;  Query:  SELECT * from TABLE (select * from properties where name=‘CityHall’) t;

20. Large-Object Types  Large objects (photos, videos, CAD files, etc.) are stored as a large object:  blob: binary large object -- object is a large collection of uninterpreted binary data (whose interpretation is left to an application outside of the database system)  clob: character large object -- object is a large collection of character data  When a query returns a large object, a pointer is returned rather than the large object itself.

21. Conversion and other Functions  TO_CHAR  Converts numbers, date, time, clob args to char strings  Can specify a format for numbers, dates  SELECT TO_CHAR(10000,'L99G999D99MI') "Amount" FROM DUAL  Returns the string: $10,000  TO_NUMBER  TO_DATE,…  SUBSTR:  SELECT SUBSTR('ABCDEFG',3,4) "Substring" FROM DUAL;  Returns the string starting at pos 3 and of length 4: ‘CDEF’  INSTR (string, pattern_to_search_for,..)  Checks if patterns is in string and returns in pos  TRIM; trims the strings from either ends

22. SQL as a DDL Using SQL to create logical schemata Example: CREATE TABLE branch ( bname char(15) NOT NULL, bcity char(30), assets int) attrattr-domains attr attr-domains What domains available? char(n), varchar(n) int float(p), numeric(p,d) e.g. numeric(3,1) allows 44.5 real date: year-mo-day e.g. ‘2004-02-05’, time: hr:min:sec e.g. ’09:30:01’ precision digits

23. SQL as DDL Can create new domains: e.g CREATE DOMAIN p-name char(15) NOT NULL Modify tables: DROP TABLE -- drops both schema and instance e.g. DROP TABLE account ALTER TABLE ADD ( ) ex. ALTER TABLE branch ADD numloans int -- new values given default value of NULL ALTER TABLE DROP ( ) ex. ALTER TABLE customer DROP cstreet

24. Authorization Forms of authorization on parts of the database:  Read - allows reading, but not modification of data.  Insert - allows insertion of new data, but not modification of existing data.  Update - allows modification, but not deletion of data.  Delete - allows deletion of data. Forms of authorization to modify the database schema (covered in Chapter 8):  Index - allows creation and deletion of indices.  Resources - allows creation of new relations.  Alteration - allows addition or deletion of attributes in a relation.  Drop - allows deletion of relations.

25. Authorization Specification in SQL  The grant statement is used to confer authorization grant on to  is:  a user-id  public, which allows all valid users the privilege granted  A role (more on this in Chapter 8)  Granting a privilege on a view does not imply granting any privileges on the underlying relations.  The grantor of the privilege must already hold the privilege on the specified item (or be the database administrator).

26. Privileges in SQL  select: allows read access to relation,or the ability to query using the view  Example: grant users U 1, U 2, and U 3 select authorization on the branch relation: grant select on branch to U 1, U 2, U 3  insert: the ability to insert tuples  update: the ability to update using the SQL update statement  delete: the ability to delete tuples.  all privileges: used as a short form for all the allowable privileges  more in Chapter 8

27. Revoking Authorization in SQL  The revoke statement is used to revoke authorization. revoke on from  Example: revoke select on branch from U 1, U 2, U 3  may be all to revoke all privileges the revokee may hold.  If includes public, all users lose the privilege except those granted it explicitly.  If the same privilege was granted twice to the same user by different grantees, the user may retain the privilege after the revocation.  All privileges that depend on the privilege being revoked are also revoked.

28. SQL Summary Query Language (DML): SELECT, FROM, WHERE GROUP BY, HAVING INTO ORDER BY Nested Queries ( IN, EXISTS, UNIQUE, ALL, SOME, correlation) Aggregates Joins Updates Views, Pseudocolumns, Connect-by Built-in Datatypes DDL: CREATE TABLE DROP TABLE CREATE DOMAIN ALTER TABLE Authorization