1. Dale Roberts 1 Department of Computer and Information Science, School of Science, IUPUI Dale Roberts, Lecturer Computer Science, IUPUI E-mail: droberts@cs.iupui.edu Basic SQL and SQLPlus - Querying using SELECT

2. Dale Roberts Relational Data Model RDBMS’s are based on the Relational Data Model. A data model is a notation for describing data. The notation generally covers conceptually how data is structured (records, structures, relations, etc.), operations on the data (queries and modifiers), and constraints (domain, cross references). The two preeminent data models are Relational – all commercial databases XML – added feature to most databases 2 (This Relational Data Model discussion comes from the Ullman text)

3. Dale Roberts Relational Terminology The Relational Data Model is based on relations. 3 titleyearlengthgenre Gone With the Wind1939231drama Star Wars1977124sciFi Wayne’s World199295comedy The relation Movies (our class standards would name this Movie.) Within the Relational Data Model, the columns are called attributes, and the rows are called tuples. The name of the relation and the set of attributes is called the schema of the relation: Movies(title, year, length, genre)

4. Dale Roberts Attributes and Tuples Attributes are a set, not a list. However, there is a “standard” order of attributes that are used for display when another order is not specified. Other than the header row, the data is a tuple where each tuple has one component per attribute. (Gone With the Wind, 1939, 231, drama) Each attribute must be atomic, meaning that each attribute must be an elementary data type like integer or string. They cannot be structured data types. 4

5. Dale Roberts Relation Instances The tuples that comprise a relation are not static over time. Tuples are inserted as new movies come out, and updated as data changes. Each set of tuples represents an instance of the relation. A conventional database system only maintains one version of the tuples that are currently in the relation. This is the current instance. 5

6. Dale Roberts Keys of a Relation A set of attributes forms a key of a relation if no two tuples can have the same values. A key is an example of a constraint. The DBMS supports many constraints, but the key constraint is so important it is discussed as part of the relation definition. Underlined attributes identify the key. The attributes title and year together can be used to identify a single Movies tuple. 6 Movies(title, year, length, genre)

7. Dale Roberts Defining a Relational Schema in SQL Terminology shift: Relation → Table or View Attribute → Column Tuple → Row A stored relation it a table. A dynamically constructed relation is a view. Temporary tables are created and dropped by the database engine as needed during queries and data modifications. 7

8. Dale Roberts Defining a Relational Schema in SQL The CREATE keyword is used in SQL to create tables and views. 8 CREATE TABLE Movies( title CHAR(100), year INT, length INT, genre CHAR(10), studioName CHAR(30), producerC# INT, PRIMARY KEY (title, year) ); CREATE TABLE MOVIE( TITLE_TXT VARCHAR2(100), YEAR_NBR NUMBER(4), LENGTH_NBR NUMBER(3), GENRE_CD VARCHAR2(10), STUDIO_NAME VARCHAR2(30), PRODUCER_CERT_NBR NUMBER(9), PRIMARY KEY (TITLE_TXT, YEAR_NBR ) ); Standard SQL Typical Enterprise Oracle SQL

9. Dale Roberts Using SELECT with Relations The SQL SELECT statement is used to query relations. SELECT statements return a result set, which itself is a relation. Because the SELECT operation is closed over the set relations, the SELECT statements can be nested to perform complex queries. 9 R1 R2 SELECT R3 M N M x N

10. Dale Roberts Using SELECT with Relations SELECT statements can be nested, and the SELECT statement itself allows many tables to participate. SELECT always produces a single result set. The relations can be tables or views or temporary tables. 10 R1 R2 SELECT R3 R1 R4 SELECT R5

11. Dale Roberts Relation Compatibility SELECT statements return a result set with shape M x N. If M=1, the result set is compatible with a list (IN keyword). If N=1, M=1, the result set is compatible with a single value. 11 M 1 1 1

12. Dale Roberts 12 The Basic Parts of Speech in SQL SQL is a language. Oracle7 SQL is a superset of the American National Standards Institute (ANSI) and the International Standards Organization (ISO) SQL92 standard at entry level conformance. PL/SQL is Oracle’s procedural language extension to SQL. It allows you to link several SQL commands through procedural language. SQL*Plus (SQLPLUS from command line) is a tool that allows users to interact with Oracle. SQL*Plus enables you to manipulate SQL commands and PL/SQL blocks, and to perform many additional tasks as well. Through SQL*Plus, you can: –enter, edit, store, retrieve, and run SQL commands and PL/SQL blocks –format, perform calculations on, store, and print query results in the form of reports –list column definitions for any table –access and copy data between SQL databases –send messages to and accept responses from an end user

13. Dale Roberts 13 The Basic Parts of Speech in SQL SQL*Plus,… very quick overview first, create/run a script to start an Oracle database instance from the command line: sqlplus or sqlplusw SQL> Common commands in SQL*Plus: get get @ @ save save list or l change or c editsave ! (shell to OS) Capitalization generally does not matter

14. Dale Roberts 14 The Basic Parts of Speech in SQL Simple Select Examples Select statement, single table query, all rows: SELECT CUSTOMER_NUMBER, LAST, FIRST, BALANCE FROM CUSTOMER ORDER BY CUSTOMER_NUMBER;... specific rows (where clause): SELECT CUSTOMER_NUMBER, LAST, FIRST, BALANCE FROM CUSTOMER WHERE CUSTOMER_NUMBER > 500;... with a calculation: SELECT CUSTOMER_NUMBER, LAST, (CREDIT_LIM - BALANCE) FROM CUSTOMER WHERE CUSTOMER_NUMBER > 500;... multiple where conditions (and): SELECT CUSTOMER_NUMBER, LAST, FIRST, BALANCE FROM CUSTOMER WHERE BALANCE >= 500 AND BALANCE <= 1000;

15. Dale Roberts 15 The Basic Parts of Speech in SQL The SELECT clause: –can be a list of columns, –an asterisk * for all columns, –a calculation (or other expressions), –group functions (chapter 9), –distinct keyword -- removes duplicates. SELECT DISTINCT SUPPLIER FROM PRODUCTS; –column names can be renamed in the output with an alias. SELECT CUSTOMER_NUMBER, LAST, FIRST, (CREDIT_LIM - BALANCE) AS REMAINING_CREDIT FROM CUSTOMER; The FROM clause: –in single tables queries, just provide your table’s name …. more on this in multi-table queries.

16. Dale Roberts 16 The Basic Parts of Speech in SQL The WHERE Clause: –this is a logical, boolean expression which must evalute to true for each row in the query’s output. –where clause comparison operators: = equal to less than, greater than = less than or equal, greater than or equal <>, !=, ^= not equal –compound conditions are built with the boolean operators AND, OR. –AND is evaluated first by default. Use parenthesis ( ) to force the order of OR/AND. –a compliment of a condition can be evaluated with NOT. Examples below are equivalent: SELECT PART_DESCRIPTION FROM PART WHERE WAREHOUSE_NUMBER != ‘3’; SELECT PART_DESCRIPTION FROM PART WHERE NOT (WAREHOUSE_NUMBER=‘3’);

17. Dale Roberts 17 The Basic Parts of Speech in SQL The WHERE Clause (continued): –BETWEEN keyword is the same as >= and =<. For example, these 2 statements are the same: SELECT CUSTOMER_NUMBER, LAST, FIRST, BALANCE FROM CUSTOMER WHERE 500 <= BALANCE AND BALANCE <= 1000; SELECT CUSTOMER_NUMBER, LAST, FIRST, BALANCE FROM CUSTOMER WHERE BALANCE BETWEEN 500 AND 1000; –LIKE keyword is used for pattern matching. ‘%’ is for any number of characters. ‘_’ (underscore) is for one character. SELECT CUSTOMER_NUMBER, LAST, FIRST FROM CUSTOMER WHERE LAST LIKE ‘JONE%’; SELECT CUSTOMER_NUMBER, LAST, FIRST FROM CUSTOMER WHERE LAST LIKE ‘JONE_’;

18. Dale Roberts 18 The Basic Parts of Speech in SQL The WHERE Clause (continued): –IN keyword provides a list of numbers or strings to compare to. This is similar to using OR with =. For example, these 2 statements are the same: SELECT CUSTOMER_NUMBER, LAST, FIRST, BALANCE FROM CUSTOMER WHERE CUSTOMER_NUMBER IN (10, 11, 12); SELECT CUSTOMER_NUMBER, LAST, FIRST, BALANCE FROM CUSTOMER WHERE (CUSTOMER_NUMBER = 10) OR (CUSTOMER_NUMBER = 11) OR (CUSTOMER_NUMBER = 12); –NULL and NOT NULL keywords: NULL does not mean 0, null means no value! Example- this statement only gets customers whom we have a complete name for: SELECT CUSTOMER_NUMBER, LAST, FIRST FROM CUSTOMER WHERE (FIRST IS NOT NULL) AND (LAST IS NOT NULL);

19. Dale Roberts 19 The Basic Parts of Speech in SQL The WHERE Clause (continued): –Values can also be compared to another query in the where clause. This is called a subquery. For example: SELECT CUSTOMER_NUMBER, LAST, FIRST, BALANCE FROM CUSTOMER WHERE CUSTOMER_NUMBER IN (SELECT CUSTOMER_NUMBER FROM CUSTOMER WHERE BALANCE > 500); This however may not work sometimes with a subquery: SELECT CUSTOMER_NUMBER, LAST, FIRST, BALANCE FROM CUSTOMER WHERE CUSTOMER_NUMBER = (SELECT CUSTOMER_NUMBER FROM CUSTOMER WHERE BALANCE > 500); because subqueries return sets of values, not a single value.

20. Dale Roberts 20 The Basic Parts of Speech in SQL The WHERE Clause (continued): –Tables can be joined by common attributes. This is done in the where clause. SELECT WEATHER.CITY, CONDITION, TEMPERATURE, LATITUDE,... FROM WEATHER, LOCATION WHERE WEATHER.CITY = LOCATION.CITY; –A shortcut (not in book). Tablenames can be aliased to save typing, reduce wordiness. SELECT W.CITY, CONDITION, TEMPERATURE, LATITUDE,... FROM WEATHER W, LOCATION L WHERE W.CITY = L.CITY; –Joining data from different tables is one of the more powerful parts of SQL. It is not without its dangers. Joining tables the wrong way (not on common attributes), the wrong data comes back. Forgetting to specify common keys in the where clause returns a “cartesian product” (each row of both tables joined to each other, m times n rows)

21. Dale Roberts 21 The Basic Parts of Speech in SQL The ORDER BY Clause: –Specifies the ordering of the returned data. –Multiple columns can be selected to sort on. –ASC is ascending order order, default. –DESC is descending sort order. SELECT FEATURE, SECTION, PAGE FROM NEWSPAPER WHERE SECTION = ‘F’ ORDER BY PAGE DESC, FEATURE ASC; Views: –Makes a query act similar to a table. –Views are “describe”-able, “select”-able –The view’s select statement is run everytime rows are selected from the view--ie data is not saved somewhere (like a table) CREATE VIEW INVASION AS SELECT W.CITY, CONDITION, TEMPERATURE, LATITUDE FROM WEATHER W, LOCATION L WHERE W.CITY = L.CITY;

22. Dale Roberts 5/19/2015 22 Acknowledgements Loney, Kevin. Oracle Database 10g The Complete Reference. McFadden and Hoffer. Database Management, pp. 214-216. Ullman, Jeffrey and Widom, Jennifer. A First Course in Database Systems.