CSCI 153 Structured Query Language (SQL). Relational Databases Data is stored in related tables –Database may be one or more tables Examples: –Access.

CSCI 153

Structured Query Language (SQL)

Relational Databases

• Data is stored in related tables– Database may be one or more tables

• Examples:– Access– SQL Server– MySQL

• RDBMS– Relational Database Management System

SQL and RDBMS

• SQL allows for easy manipulation of data– SELECT (selecting a record(s))– INSERT (adding a record)– UPDATE (changing a record(s))– DELETE (deleting a record(s))

• Tables can be created or deleted– CREATE – DROP

SELECT Statement

SELECT Player_Stats.T_Code, Player_Stats.Player_FName, Player_Stats.Player_LName, Player_Stats.Hits, Player_Stats.At_Bats, Player_Stats.Home_Runs, Player_Stats.Triples, Player_Stats.Doubles FROM Player_Stats;

Result – See Demo Query 1

SELECT Statement

SELECT T_Code, Player_FName, Player_LName, Hits, At_Bats, Home_Runs, Triples, Doubles FROM Player_Stats;

Result – See Demo Query 1

SELECT Statement

SELECT * FROM Player_Stats;

Result – See Demo Query 1

SELECT Statement

SELECT * FROM Player_Stats WHERE Home_Runs > 25;

Result – See Demo Query 2

SELECT Statement

SELECT * FROM Player_Stats WHERE Home_Runs > 25 AND Doubles > 30;

Result – See Demo Query 3

SELECT Statement usingLike Wildcard

Select * FROM Team_Codes WHERE T_Code Like 'NLE*'

Result – See Demo Query 7

SELECT Statement usingOrder By statement

SELECT * FROM Team_Codes WHERE T_Code Like 'NLE*' ORDER BY Team_Name;

Result – See Demo Query 8

SELECT From 2 tables using a union

SELECT * FROM Player_Stats, Team_Stats

Result – See Demo Query 9

• This will result in n*m rows where Table_1 has n rows, and Table_2 has m rows(144 rows in this case)

SELECT From 2 tables using a join SELECT Player_FName, Player_LName, Team_City,

Team_Name FROM Team_Codes, Player_Stats WHERE Team_Codes.T_Code = Player_Stats.T_Code

Result – See Demo Query 10

SELECT using formulas SELECT Player_LName, (Hits/At_Bats) FROM Player_Stats;

Result – See Demo Query 11

SELECT – Renaming fields SELECT Player_LName, (Hits/At_Bats) AS Avg

FROM Player_Stats

Result – See Demo Query 12

Data Abstraction

INSERT Statement

INSERT INTO Team_Codes (T_Code, Team_City, Team_Name) VALUES ('ALE1', 'Baltimore', 'Orioles')

Inserts a row into table (does not display anything)

Inserts represented by a + icon in Access

INSERT Statement

INSERT INTO Team_Codes Values ('ALE2', 'Boston', 'Red Sox')

Inserts a row into table – sets the values according to the default field order (does not display anything)

UPDATE Statement UPDATE Player_Stats

SET Home_Runs = 42 WHERE Player_LName = 'Piazza'

• Changes the row in the table associated with Piazza – sets his home runs to 42 (nothing is displayed)

• Updates represented by a pencil icon in Access

UPDATE Statement

UPDATE Player_Stats SET Home_Runs = 0

• Changes all of the rows in the table – sets home runs to 0 (nothing is displayed)

• Unconditional – BE VERY CAREFUL

DELETE Statement

DELETE FROM Team_Codes WHERE T_Code='ALE1';

• Deletes row from table (nothing is displayed)

• Deletes represented by an X icon in Access

DELETE Statement

DELETE FROM Team_Codes

• Deletes all rows in the table (nothing is displayed)

• Unconditional – BE VERY CAREFUL

HAVING and GROUP BY

SELECT T_Code, SUM(Home_Runs)

FROM Player_Stats

WHERE T_Code LIKE 'NLE*'

GROUP BY T_Code

HAVING SUM(Home_Runs) > 85

• ORDER BY and WHERE can not be used with aggregate functions– replaced by GROUP BY and HAVING respectively

CREATE Statement

CREATE TABLE Sports (Sport_ID AUTOINCREMENT, Sport_Name TEXT NOT NULL, Number_Teams INT)

• Creates a table named Sports with 3 columns

DROP Statement

DROP TABLE Sports

• Unconditionally deletes the table