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DBS201: More on SQL

Lecture 2

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Agenda

Review How to create a table How to insert data into a table Terms Lab 2

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Review

Data Anomalies What is a database? What is a DBMS? What are three categories of SQL statements

Use three letters to describe each category On IBM i platform What command is used to initiate an interactive SQL

session? How do you construct a container for Tables and Views A collection is also called two other names - ?

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How to Create a Table

First write a Database Structure chart. We can also call this a Data Dictionary of

your table.

Column Type Length PK FK reference Req’d ?

Unique ?

Validation

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How to Create a Table

Type: Numeric Decimal Character Varchar Date

‘yyyy-mm-dd’ Do not specify a length

Time Length:

Specify positions to the left of the decimal point and positions to the right of the decimal point

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How to Create a Table

Primary Keys For concatenated Primary Keys, pay close attention

to the order of the attributes within the Primary Key

Indexing starts with the first attribute mentioned, then proceeds to the next attribute and so on

PK: Specify ‘Y’ if this column name is a part of the PK,

otherwise leave blank

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How to Create a Table

FK Reference: Specify the table name and the column name

where this field is a PK Req’d?:

PKs, by default are required If this column must be present, specify ‘Y’ Means that this column can not be left blank or

NULL – enforces data integrity

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How to Create a Table

Unique?: Means only that the value can only appear once in

this column Validation:

Specify the range of values or the specific values that are allowed for this column

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Definition of a Table

Format for defining the table PAINTER:

Column Type Len PK FK Req’d Unique Validation

PTR_NUM CHAR 4 Y Y Y

PTR_LNAME CHAR 15 Y

PTR_FNAME CHAR 15 Y

PTR_CITY CHAR 20

PTR_PHONE DEC 10

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Creating a ‘Database’

CREATE COLLECTION Used to create a ‘database’

Syntax CREATE COLLECTION ‘database name’

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Deleting a ‘Database’

To remove a ‘database’, use the DROP COLLECTION statement

Syntax DROP COLLECTION ‘database name’

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Creating Tables in SQL

CREATE TABLE Used to create a table

Syntax CREATE TABLE tablename (field1 datatype fieldsize,

field2 datatype fieldsize, ….CHECK …,

PRIMARY KEY (fieldname(s)), FOREIGN KEY (fieldname) REFERENCES tablename (PKfieldname))

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Creating Tables in SQL

Create statement for painter might look like:

CREATE TABLE painter (

p_num char (4) not null with default primary key,

p_lname char (15) not null with default,

p_fname char (15) not null with default,

p_city char (20),

p_phone dec (10))

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Creating Tables in SQL

Use this version on tests and exam CREATE TABLE painter ( p_num char (4) not null with default, p_lname char (15) not null with default, p_fname char (15) not null with default, p_city char (20), p_phone dec (10), Constraint Painter_p_num_PK Primary Key (p_num) )

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Creating Tables in SQL

Primary Key Constraint initially not done: Table created without a primary key constraint p_phone dec (10) )

ALTER TABLE PAINTER ADD CONSTRAINT PAINTER_p_num_PK PRIMARY KEY (p_num)

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Dropping Tables in SQL

DROP TABLE Used to remove a table

Syntax DROP TABLE tablename

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Inserting Data into a Table

INSERT Used to insert data into a table

Syntax INSERT INTO tablename (fieldname1, fieldname2,

….) VALUES (value1, value2…)

or INSERT INTO tablename VALUES (value1,

value2…), (value1, value2…)

Multiple rows added

Single row added

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Inserting Data into a Table

Rules for Inserting: Include all column names and provide values for

each column Or Ignore column names and provide values in the

same order as column names If table was created allowing NULLs, then indicate

the word NULL in place of that column when specifying the values

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Primary Keys in SQL

Primary Key

Primary Key must always be NOT NULL (and unique)

What happens if you create the table without specifying a primary key, insert rows and then apply the primary key constraint?

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Inserting a Row

INSERT INTO PAINTERA40/PAINTER VALUES('111', 'Smith', 'Bill', 'Oakville', 905477333)INSERT INTO PAINTERA40/PAINTER VALUES('222', 'Brown', 'Nancy', 'Mississauga', 9055666633)

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Inserting Data into a Table

INSERT INTO PAINTERA40/PAINTER (p_num, p_lname, p_fname, p_city, p_phone) VALUES('111','Wong', 'Ben', 'Newmarket', 9058876644)

Can we add the primary key constraint ? ALTER TABLE PAINTER ADD CONSTRAINT Painter_p_Num_PK PRIMARY KEY (P_Num) Unique index cannot be created because of duplicate

keys.

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SQL Terminology

S C H E M A

A group of related objects that consists of a library, a journal, a journal receiver, an SQL catalog, and an optional data dictionary.

A schema enables the user to find the table, view and index objects by name. Another name for a schema is collection.

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SQL Terminology

T A B L E A set of columns and rows. R O W The horizontal part of a table containing a

serial set of columns. C O L U M N The vertical part of a table of one data type

Equivalent SQL Terminology

L I B R A R Y A group of related objects that enables the user to

find the objects by name.

A schema is treated the same as a library by some native commands.

P H Y S I C A L F I L E A set of records. A Table is treated the same as a Physical File by

native and SQL commands

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Equivalent SQL Terminology

R E C O R D A set of fields. F I E L D One or more bytes of related information of

one data type. In SQL this is referred to as a column.

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PART Table – What can you identify?

PARTNUMBER

PARTDESC

ONHAND CLASS WAREHOUSE PRICE

AX12 Iron 104 HW 3 23.95

AZ52 Dartboard 20 SG 2 12.95

BA74 Basketball 40 SG 1 29.95

BH22 Cornpopper 95 HW 3 24.95

BT04 Gas Grill 11 AP 2 149.99

BZ66 Washer 52 AP 3 399.99

CA14 Griddle 78 HW 3 39.99

CB03 Bike 44 SG 1 299.99

CX11 Blender 112 HW 3 22.95

CZ81 Treadmill 68 SG 2 349.99

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Table Exercise 1:

Create a table called AGENT using the following data dictionary:

Insert the following data into your table:AGT_NUM AGT_LNAME AFT_FNAME AGT_AREACODE AGT_PHONE

5 Andrews Mark 416 123-3456

10 Chen Terry 250 333-4059

15 DaSilva Lila 416 234-5837

20 Edwards George 416 444-5959

25 Eustace Gina 519 948-8494

Column Type Len PK FK Req’d Unique Validation

AGT_NUM CHAR 3 Y Y

AGT_LNAME CHAR 25 Y

AGT_FNAME CHAR 20 Y

AGT_AREACODE CHAR 3

AGT_PHONE CHAR 7

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Table Exercise 2:

Create a table using the following data dictionary:

Insert the following data into your table:CUST_NUM CUST_LNAME CUST_FNAME CUST_AREACODE CUST_PHONE

5 Andrews Mark 416 123-3456

10 Chen Terry 250 333-4059

15 DaSilva Lila 416 234-5837

20 Edwards George 416 444-5959

25 Eustace Gina 519 948-8494

Column Type Len PK FK Req’d Unique Validation

CUST_NUM DEC 3 Y Y Y 1-100

CUST_LNAME CHAR 25 Y

CUST_FNAME CHAR 20 Y

CUST_AREACODE CHAR 3

AGENT_NUM CHAR 3 AGENT

(AGENT_NUM)

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Agenda

Lab 2