1. Relational Databases and SQL The relational model and the most common SQL commands

2. Entities and Relations Entities are combinations of values Table consists of columns and rows A row is an entity, a.k.a. tuple A column is an attribute of an entity Relations can exist between columns of tables

3. Structured Query Language Structured Query Language (SQL) is the set of statements with which all programs and users access data in an Oracle database

4. Structured Query Language Create and remove tables Insert rows into tables Change rows in tables Delete rows from tables Search in tables and combinations thereof

5. Data types VARCHAR2(size) NUMBER(p,s) CHAR(size) BLOB FLOAT(b) INTEGER

6. VARCHAR2(size) Variable-length character string having maximum length size bytes. Maximum size is 4000 bytes, and minimum is 1 byte. You must specify size for VARCHAR2.

7. NUMBER(p,s) Number having precision p and scale s. The precision p can range from 1 to 38. The scale s can range from -84 to 127. NUMBER(6)123456 NUMBER(6,2)1234,56 NUMBER(6,-2)1200

8. CHAR(size) Fixed-length character data of length size bytes. Maximum size is 2000 bytes. Default and minimum size is 1 byte.

9. BLOB A binary large object. Maximum size is 4 gigabytes.

10. FLOAT(b) & INTEGER FLOAT(b) specifies a floating-point number with binary precision b. The precision b can range from 1 to 126. INTEGER :== NUMBER(38)

11. The NULL value NULL marks an attribute undefined NULL is a valid value of ANY data type Unspecified attributes get the NULL value NULL is not equal to any value but NULL is equivalent to NULL The function NVL(x,y) returns y if x equivalent NULL, else it returns x

12. Tables CREATE TABLE sources ( nameVARCHAR2(10), raFLOAT, decFLOAT, bmagNUMBER(5, 2), rmagNUMBER(5, 2) ); DROP TABLE sources;

13. Adding rows to a table INSERT INTO sources ( name, ra, dec, bmag, rmag ) VALUES ( 'NGC7072', 21.45694, -43.37306, 14.31, 13.33 );

14. Adding rows to a table INSERT INTO sources VALUES ( 'NGC7072', 21.45694, -43.37306, 14.31, 13.33 ); INSERT INTO sources (name, rmag) VALUES ('NGC891', 16.45);

15. Simple selection (1) SELECT * FROM sources WHERE name = 'NGC7072'; result: NAME RA DEC BMAG RMAG ---------- ---------- ---------- -------- -------- NGC7072 21.45694 -43.37306 14.31 13.33

16. Simple selection (2) SELECT name, ra, dec FROM sources WHERE bmag > 13; result: NAME RA DEC ---------- ---------- ---------- NGC7072 21.45694 -43.37306

17. Simple selection (3) SELECT name, bmag-rmag FROM sources WHERE bmag > 13 AND rmag < 19; result: NAME BMAG-RMAG ---------- NGC7072.98

18. Simple selection (4) SELECT DISTINCT SUBSTR(name, 1, 3) FROM sources; result: SUB --- NGC

19. Simple selection (5) SELECT x.rmag, x.bmag FROM sources x WHERE x.rmag < x.bmag; result: RMAG BMAG ---------- 13.33 14.31

20. Deleting rows from a table DELETE FROM sources WHERE name like 'NGC70__'; DELETE FROM sources WHERE name like 'NGC70%'; TRUNCATE TABLE sources; efficiently deletes ALL rows

21. Changing values in rows UPDATE sources SET rmag = rmag / 10, bmag = bmag * 10 WHERE name IS NOT NULL;

22. Joining tables SELECT b.name, b.ra, b.dec, b.mag bmag, r.mag rmag FROM bsources b, rsources r WHERE b.name = r.name; result: NAME RA DEC BMAG RMAG ---------- ---------- ---------- ---------- ---------- NGC1234 12.34 45.67 17.3 19.3 NGC4321 23.45 56.78 18.2 17.2