1. 1 Dept. of CIS, Temple Univ. CIS616/661 – Principles of Data Management V. Megalooikonomou SQL (part 2) (based on slides by C. Faloutsos at CMU)

2. Overview - detailed - SQL DML select, from, where, renaming, ordering, aggregate functions, nested subqueries insertion, deletion, update other parts: DDL, embedded SQL, auth etc

3. Data Definition Language create table student (ssn char(9) not null, name char(30), address char(50), primary key (ssn) )

4. Data Definition Language create table r( A1 D1, …, An Dn, integrity-constraint1, … integrity-constraint-n)

5. Data Definition Language Domains: char(n), varchar(n) int, numeric(p,d), real, double precision float, smallint date, time

6. Data Definition Language integrity constraints: primary key foreign key check(P)

7. Data Definition Language create table takes (ssn char(9) not null, c-id char(5) not null, grade char(1), primary key (ssn, c-id), check grade in (“A”, “B”, “C”, “D”, “F”))

8. Data Definition Language delete a table: difference between drop table student delete from student

9. Data Definition Language modify a table: alter table student drop address alter table student add major char(10)

10. Overview - detailed - SQL DML select, from, where, renaming, ordering, aggregate functions, nested subqueries insertion, deletion, update other parts: DDL, embedded SQL, auth etc

11. Embedded SQL from within a ‘host’ language (eg., ‘C’, ‘VB’) EXEC SQL END- EXEC Q: why do we need embedded SQL??

12. Embedded SQL SQL returns sets; host language expects a tuple - impedance mismatch! solution: ‘cursor’, ie., a ‘pointer’ over the set of tuples. example:

13. Embedded SQL main(){ … EXEC SQL declare c cursor for select * from student END-EXEC …

14. Embedded SQL - ctn’d … EXEC SQL open c END-EXEC … while( !sqlerror ){ EXEC SQL fetch c into :cssn, :cname, :cad END-EXEC fprintf( …, cssn, cname, cad); }

15. Embedded SQL - ctn’d … EXEC SQL close c END-EXEC … } /* end main() */

16. dynamic SQL main(){ /* set all grades to user’s input */ … char *sqlcmd=“ update takes set grade = ?”; EXEC SQL prepare dynsql from :sqlcmd ; char inputgrade[5]=“a”; EXEC SQL execute dynsql using :inputgrade; … } /* end main() */

17. Overview - detailed - SQL DML select, from, where, renaming, ordering, aggregate functions, nested subqueries insertion, deletion, update other parts: DDL, embedded SQL, auth etc

18. SQL - misc Later, we’ll see authorization: grant select on student to transactions other features (triggers, assertions etc)

19. General Overview - rel. model Formal query languages rel algebra and calculi Commercial query languages SQL QBE, (QUEL)

20. Rel. model - QBE Inspired by the domain relational calculus “P.” -> print (ie., ‘select’ of SQL) _x, _y: domain variables (ie., attribute names) Example: find names of students taking 15-415

21. Rel. model - QBE

23. names of students taking 15-415

24. Rel. model - QBE condition box self-joins (Tom’s grandparents) ordering (AO., DO.) aggregation (SUM.ALL., COUNT.UNIQUE., …) group-by (G.)

25. Rel. model - QBE aggregate: avg grade overall:

26. Rel. model - QBE aggregate: avg grade per student:

27. General Overview - rel. model Formal query languages rel algebra and calculi Commercial query languages SQL QBE, (QUEL)

28. Rel. model - QUEL Used in INGRES only - of historical interest. Eg.: find all ssn’s in mini-U: range of s is student; retrieve (s.ssn);

29. Rel. model - QUEL general syntax: range of …. is t-name retrieve (attribute list) where condition SQL select attr. list from t-name where condition

30. Rel. model - QUEL very similar to SQL also supports aggregates, ordering etc

31. General Overview Formal query languages rel algebra and calculi Commercial query languages SQL QBE, (QUEL) Integrity constraints Functional Dependencies Normalization - ‘good’ DB design