First lecture of this chapter is in slides (PPT file)

Transcription

1 First lecture of this chapter is in slides (PPT file)

2 Review of referential integrity CREATE TABLE other_table ( b1 INTEGER, c1 INTEGER, PRIMARY KEY (b1, c1) ) CREATE TABLE t ( a integer PRIMARY KEY, b2 integer, c2 integer, FOREIGN KEY (b, c) REFERENCES other_table (b1, c1) ) Let s say that other_table exists, but does not yet have the primary key defined. How do we add a primary key (or any other constraint) to a table? (p.131)

3 Let s say that a tuple (b1, c1) is deleted from other_table. What happens to the referencing tuples from t? Let s say that a tuple (b1, c1) is updated in other_table

4 Actions possible (pp ): RESTRICT / NO ACTION CASCADE SET NULL / SET DEFAULT

5 CREATE TABLE R ( A INTEGER, B INTEGER ) CREATE ASSERTION ab CHECK ( (SELECT COUNT (*) FROM R AS R1, R AS R2 WHERE (R1.B!= R2.B) AND (R1.A = R2.A)) =0) What exactly does the above assertion imply?

6 Review of authorization (4.3) Forms of authorization to query/modify DB instance: 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 DB 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. grant <privilege list> on <relation name or view name> to <user list> grant select on branch to U1, U2, U3 revoke <privilege list> on <relation name or view name> from <user list> revoke select on branch from U1, U2, U3

7 4.4 Embedded SQL EXEC SQL <embedded SQL statement > END_EXEC EXEC SQL open c END_EXEC EXEC SQL fetch c into :cn, :cc END_EXEC Repeated calls to fetch get successive tuples in the query result A variable called SQLSTATE in the SQL communication area (SQLCA) gets set to to indicate no more data is available EXEC SQL close c END_EXEC

8 Example: Add $100 to all account at Perryridge branch. EXEC SQL declare c cursor for select * from account where branch_name = Perryridge for update ; EXEC SQL open c; while(sqlstate!= ) EXEC SQL update account set balance = balance where current of c ; EXEC SQL close c;

9 If you really want to know (not in text, not required) This is the SQLCA in C: #include <SQLCA.H> typedef struct { char sqlcaid[8]; long sqlcabc; long sqlcode; struct { short sqlerrml; char sqlerrmc [70]; } sqlerrm; struct { char sqlwarn0; char sqlwarn1; char sqlwarn2; char sqlwarn3; char sqlwarn4; char sqlwarn5; char sqlwarn6; char sqlwarn7; } sqlwarn char sqlext[8]; } SQLCA; sqlerrml is set to 1 an error has been encountered, otherwise it is set to 0. sqlcode is an integer which is set as follows: o 0 = Statement executed successfully. o < 0 = An error has occurred. The value is the negative of the error number sqlcode = : row containing empty fields encountered. o > 0 = Statement executed successfully but some exceptional condition has occurred, e.g. no data processed (empty field encountered). sqlcode = 100: empty row encountered.

10 4.5 Dynamic SQL Example of the use of dynamic SQL from within a C program. char * sqlprog = update account set balance = balance * 1.05 where account_number =? EXEC SQL prepare dynprog from :sqlprog; char account [10] = A-101 ; EXEC SQL execute dynprog using :account;

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12 Null-terminated string

13 4.6 Functions and Procedural Constructs in SQL

14 Since SQL 2003, functions can return tables as well

15 What is the difference between functions and procedures? Global variable!

16 Procedural constructs (since SQL 1999):

17 Can we do this with non-procedural SQL?

18 Can we do this with non-procedural SQL?

19 Exception conditions: Explicitely defined (exit, continue, execute_error_handling_function) Predefined (sqlexception, sqlwarning, not found) READ: Extended example on p.149 of text. READ: Section External Language Routines

20 4.7 Recursive queries Transitive closure: find all employees managed (directly or indirectly) by Jones

21 READ and understand the iterative solution (Sec.4.7.1) SKIP Sec. 4.8 Homework for Ch.4: 3, 4, 5, 10, 11, 13 Due next Friday, March 11, before the midterm