Lists, Views, Describing tables Kris Pepper

Where are we Finishing up integrity, sets and lists, and now adding in views and describe. Finishing homework 3. Starting final project.

LIST Compare two lists of similar attributes IN >ANY >SOME >ALL

List Comparison - in Compare to values in a list - in or not in List student first names of sid 1111 and 2222 Select distinct fname from students where SID in (1111, 2222); Result: Nandita Sydney SID SIDName 1111Nandita 2222Sydney 3333Susan 4444Naveen 5555Elad 6666Lincoln 7777new

List Comparison - in Can use a subquery to create the list: List student first names who are enrolled in term f96 Select distinct SID from enrolls where term = ‘f96’); Select fname from students where sid in (select distinct sid from enrolls where term = ‘f96’); RESULT: FNAME Nandita Sydney Susan Naveen SID SIDName 1111Nandita 2222Sydney 3333Susan 4444Naveen 5555Elad 6666Lincoln 7777new

Try One List first names of students in course 1030, 1031 or 1035 Steps: 1: write the base query on students ending with IN (a list of SIDS in the course). 2: write a query of enrolls listing sids in these courses.

Answer List List first names of students in course 1030, 1031 or 1035 Steps: 1: write the base query on students ending with IN (a list of SIDS in the course). Select fname from students where sid in (a list of SIDS in the course) 2: write a query of enrolls listing sids in these courses. Select distinct sid from enrolls where lineno in (1030, 1031, 1035) 3. Put it together: Select fname from students where sid in (Select distinct sid from enrolls where lineno in (1030, 1031, 1035));

List Comparison - any, all, some >,,=, >=, <= Select student ids with scores greater than all in the list: Select distinct sid from scores where points >= all (90, 340, 70) Substitute a query listing all points

List Comparison - any, all, some Select scores greater than all in the list: Select distinct sid from scores where points >= all (select points from scores); 1111 You try: List student ids with scores less than all in the list

List Comparison - any, all, some Answer: Select distinct sid from scores where points <= all (select points from scores); 2222 Try one more: List student ids with scores which are greater than the average score

List Comparison - any, all, some Not a list answer Answer: Select distinct sid from scores where points < (select avg(points) from scores);

Sub-Query using outer Sub query acts for every row in the main (outer) query Use the fields from the outer query in the inner query List of courses in which all individual components grades are higher than B: Select term, lineno, cno from courses where b <all (select points from scores where scores.lineno = courses.lineno and scores.term = courses.term);

Exists If subquery has any row in result, then exists is TRUE If no row results, then FALSE Select all courses in which 1111 is enrolled: select distinct cno from courses where exists (select 'a' from enrolls where courses.lineno = enrolls.lineno and sid = ‘1111’); You try: list all the fields from the student table where any score is greater than 90. (use exists)

Exists Answer: select * from students where exists (select ‘a’ from scores where students.sid = scores.sid and points > 90);

Important Stuff Database checks integrity Subqueries help make lists for where conditions In, All, Some, Any Exists

Views Like creating a new table, but only doesn’t physically hold data. Can use in other queries. Format: CREATE VIEW Viewname AS Select statement

VIEWS - SAMPLE SQL> create view sids_in_course as select distinct sid from enrolls where lineno in (1030, 1031, 1035); View created. SQL> select * from sids_in_course; SID Use it in the query from before: Select fname from students where sid in (select * from sids_in_course);

VIEWS Try one: Create a new view called course_with_name listing all the courses with the course number and name (linking courses and catalog) When you are done, format the columns: column ctitle format a10 column lineno format 9999 Select * from course_with_name; Select * from cat; Create view course_with_name as select courses.*, ctitle from courses, catalog where courses.cno = catalog.cno; Select * from course_with_name

Describe tables Define with CREATE, ALTER, DROP Describe command shows basic info All definitions stored in system tables TableContents catTable names user_objectsTable level info (last changed date, etc) Also, all other types of ojects, like triggers and views user_tablesTable level info (Space and statistics) colsField definition information user_viewsSee complete view definition user_constraintsConstraints (primary key, foreign key and check) User_cons_columnsFields that are constrained

Some commands to describe select * from cat; select view_name, text from user_views;

cols SQL> column table_name format a10 SQL> column column_name format a10 SQL> column data_type format a10 SQL> column data_default format a10 select table_name, column_name, data_type, data_length, data_precision, data_default, nullable from cols TABLE_NAME COLUMN_NAM DATA_TYPE DATA_LENGTH DATA_PRECISION DATA_DEFAU N ODETAILS QTY NUMBER 22 Y ORDERS ONO NUMBER 22 5 N ORDERS CNO NUMBER 22 5 Y

User_cons_columns select column_name, constraint_name, position from user_cons_columns where table_name = 'ORDERS'; COLUMN_NAM CONSTRAINT_NAME POSITION ONO SYS_C ONO SYS_C CNO SYS_C ENO SYS_C

user_constraints Table_name = table that has the constraint R_constraint_name = foreign key constraint Constraint_type = P = primary key; R = foreign key

Query on user_constraints select constraint_name, constraint_type, r_constraint_name, search_condition from user_constraints where table_name = 'COURSES‘ CONSTRAINT_NAME CONSTRAINT R_CONSTRAI SEARCH_CON SYS_C C "TERM" IS NOT NULL SYS_C C "LINENO" IS NOT NULL SYS_C C "CNO" IS NOT NULL SYS_C C a > 0 SYS_C C b > 0 SYS_C C c > 0 SYS_C C d > 0 SYS_C P SYS_C R SYS_C00113

Showing primary keys select f.table_name, f.constraint_name, f.column_name from user_constraints k, user_cons_columns f where k.table_name = f.table_name and k.constraint_name = f.constraint_name and k.constraint_type = 'P' ; TABLE_NAME CONSTRAINT_NAME COLUMN_NAM COMPONENTS SYS_C TERM COMPONENTS SYS_C LINENO COMPONENTS SYS_C COMPNAME ENROLLS SYS_C SID ENROLLS SYS_C TERM ENROLLS SYS_C LINENO

Foreign keys TABLE_NAME CONSTRAINT_NAME COLUMN_NAM COMPONENTS SYS_C LINENO COMPONENTS SYS_C COMPNAME ENROLLS SYS_C SID ENROLLS SYS_C TERM ENROLLS SYS_C LINENO TEST9 SYS_C FIELD1 select f.table_name, f.constraint_name, f.column_name from user_constraints k, user_cons_columns f where k.r_constraint_name = f.constraint_name and k.constraint_type = 'R' ;

Checks select f.table_name, f.constraint_name, f.column_name, k.search_condition from user_constraints k, user_cons_columns f where k.table_name = f.table_name and k.constraint_name = f.constraint_name and k.constraint_type = 'C' ; TABLE_NAME CONSTRAINT_NAME COLUMN_NAM SEARCH_CON STUDENTS SYS_C LNAME "LNAME" IS NOT NULL COURSES SYS_C TERM "TERM" IS NOT NULL COURSES SYS_C LINENO "LINENO" IS NOT NULL

Important Stuff Database checks integrity Subqueries help make lists for where conditions In, All, Some, Any Exists Views remain Data dictionary can be queried