1. Lab 13
Databases and SQL

2. Useful information Last lab of the semester .
Next week there will be a lab exam .
No assignments for this lab.

3. Databases
Data :
facts and statistics collected together for reference or analysis
Database :
A database is a collection of one or more relations,
where each relation is a table with rows and columns
RDBMS :
It contains a set of relations

4. Database Table attributes (or columns) customer_name customer_street
customer_city
Jones
Smith
Curry
Lindsay
Main
North
Park
Harrison
Rye
Pittsfield
tuples
(or rows)

5. RDBMS Relation: made up of 2 parts:
Instance : a table , with rows and columns. #Rows = cardinality, #fields = degree / arity.
Schema : specifies name of relation, plus name and type of each column.
E.G. Students(sid: string, name: string, login: string, age: integer, gpa: float )

6. SQL –Structured Query Langauage
Developed by IBM (system R) in the 1970s
Vendors
Oracle
MYSQL
MS-SQL server
IBM DB2

7. SQL –Structured Query Langauage
Activity I : SELECT Tutorial from BBC TABLE
Hint: SELECT >>FROM >>WHERE
SELECT is the data extraction operator.You can choose the attributes here (columns),’ * ‘ returns all the columns from the table
FROM :Table name is defined here.
WHERE : It is used to limit the rows according to the condition/s.

8. SQL –Structured Query Langauage
Activity I : SELECT Tutorial from BBC TABLE
2.Relational operators same as c++
=(no double sign here like c++) ,>,<,<=,>=,!=
Note :there is no operator like !< .Just use > instead
3.per capita GDP is the GDP divided by the population GDP/population
Calculations are usually done in select clause .A new column is created with the calculation .It is a better practice to use an alias for a calculated column .
Aliases :
Aliases are defined in the from clause, called in select and where clauses . Eg.Select t.id from table as t ( Alternatively used as “from table t” without “as”.Here we create a new column called percaptaGDP using the formula) .

9. SQL –Structured Query Langauage
Activity I : SELECT Tutorial from BBC TABLE 4. SQL aggregate functions returns a single value, calculated from values in a column. Useful aggregate functions: Used on column with quantitative data AVG() - Returns the average value COUNT() - Returns the number of rows ROUND()-Returns after rounding the number MAX() - Returns the largest value MIN() - Returns the smallest value SUM() - Returns the sum

10. SQL –Structured Query Langauage
Activity I : SELECT Tutorial from BBC TABLE 6. The SQL LIKE Operator The LIKE operator is used to search for a specified pattern in a column. SQL LIKE Syntax: SELECT column name(s) FROM table name WHERE column name LIKE pattern; % operator is used inside the like operator. Ex. ‘%United’–Returns strings which ends with with United ‘United%’ -Returns string which starts with United ‘%United%’-Returns string which contains Unitedanywhere in the field.

11. SQL –Structured Query Langauage
Activity I : SELECT Tutorial from BBC TABLE
5.The IN Operator
The IN operator allows you to specify multiple values in a WHERE clause.
SQL IN Syntax
SELECT column_name(s) FROM table_name WHERE column_name IN (value1,value2,...);

12. SQL –Structured Query Langauage
ActIivity 2:More practice with SELECT: Additional practice of the basic features using a table of Nobel Prize winners.

13. SQL joins
An SQL JOIN clause is used to combine rows from two or more tables, based on a common field between them.
The most common type of join is: SQL INNER JOIN (simple join). An SQL INNER JOIN returns all rows from multiple tables where the join condition is met.

14. Questions?