00-SQL NEEDED FOR DBS201
CONTENT:
COLLECTION
ADDING A COLLECTION
DELETING A COLLECTION
TABLE
ADDING A TABLE
CHANGING the characteristics or properties of the table
DELETING A TABLE
DATA
ADDING DATA TO A TABLE
CHANGING DATA IN A TABLE
DELETING DATA FROM A TABLE
OTHER IMPORTANT TOPICS
CONSTRAINTS
VIEWS
JOINS
Note: You can execute all these commands on DB2 on the iSeries (fmly: AS400). If you wanted to
you can cut and paste them, but unless you typeor practice writing them out and also
try ideas of your own  how will you ever learn them for a test.
Note: I use PREMTARR, but you should use some other collection name throughout the code. Do a global
replace on all these commands.
COLLECTIONS
Creating a collection
CREATE COLLECTION PREMTARR
Deleting, Removing or Dropping a collection
DROP COLLECTION PREMTARR
Recreate the dropped collection
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TABLES
Creating a table
What do you want to do?
 CREATE
What do you want to create?
 TABLE
What name?
 CUSTOMER
What is the data called (columns), the type of data and the length of the data
Finally, what constraints do you want to apply to ensure data integrity
CREATE TABLE PREMTARR.CUSTOMER
(CUSTOMER_NUMBER CHAR (3)
NOT NULL WITH DEFAULT,
LAST_NAME
CHAR (15) NOT NULL WITH DEFAULT,
FIRST_NAME
CHAR (16) NOT NULL WITH DEFAULT,
STREET
CHAR (15) NOT NULL WITH DEFAULT,
CITY
CHAR (15) NOT NULL WITH DEFAULT,
PROVINCE
CHAR (2)
NOT NULL WITH DEFAULT,
POSTAL_CODE
CHAR (6)
NOT NULL WITH DEFAULT,
CREDIT_LIMIT
DECIMAL (5, 0) NOT NULL WITH DEFAULT,
BALANCE
DECIMAL (6 , 2) NOT NULL WITH DEFAULT,
SALES_REP_NUMBER CHAR (2)
NOT NULL WITH DEFAULT,
CONSTRAINT
PREMTARR.CUSTOMER_NUMBER_PK
PRIMARY KEY (CUSTOMER_NUMBER)
)
Simplified Form
CREATE TABLE PREMTARR.CUSTOMER
(CUSTOMER_NUMBER CHAR (3),
LAST_NAME
CHAR (15) NOT NULL,
FIRST_NAME
CHAR (16) NOT NULL,
STREET
CHAR (15) NOT NULL,
CITY
CHAR (15) NOT NULL,
PROVINCE
CHAR (2)
NOT NULL,
POSTAL_CODE
CHAR (6)
NOT NULL,
CREDIT_LIMIT
NUMERIC (5),  not all columns have to be NOT NULL
BALANCE
DECIMAL (6, 2) NOT NULL WITH DEFAULT 0.00,
SALES_REP_NUMBER CHAR (2) ,  say nothing and it allows NULLS
CONSTRAINT
PREMTARR.CUSTOMER_NUMBER_PK
PRIMARY KEY (CUSTOMER_NUMBER)
)
Only one of many constraints are shown
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Removing a table
Get rid of the table from the collection
DROP TABLE PREMTARR.CUSTOMER
Simplified
DROP TABLE CUSTOMER
Recreate the table again. You can do it quickly with the F9 key
Create another table SALESREP
Note the use of PK means it is NOT NULL and UNIQUE
CREATE TABLE PREMTARR.SALESREP
(SALES_REP_NUMBER CHAR (2),
SALES_REP_NAME
CHAR (15),
CONSTRAINT
PREMTARR.SALES_REP_NUMBER_PK
PRIMARY KEY (SALES_REP_NUMBER))
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Changing a Table
Remember this is about changing the structure of the table and the constraints and NOT the data.
Now set up the FOREIGN KEY constraint. You can do this when the table is being created, or it can
be added after. You have already created a table and deleted (dropped) a table, the only thing else
you can do with a table is modify it. This next step modifies a table.
Adding a constraint
First say what you want to do  alter a table
Next say what altering are you going to do
 ADD or DROP
 constraint or column
Here we are adding a foreign key constraint
ALTER TABLE PREMTARR.CUSTOMER
ADD CONSTRAINT PREMTARR.CUST_SALES_REP_FK
FOREIGN KEY (SALES_REP_NUMBER)
REFERENCES PREMTARR.SALESREP (SALES_REP_NUMBER)
ON DELETE NO ACTION  you can ignore these 2 lines
ON UPDATE NO ACTION 
Adding a column
ALTER TABLE PREMTARR.CUSTOMER
ADD COLUMN
COMM_RATE
DECIMAL (3,2)
When you add a column you need the type and length of the data to be stored just as in a create
table
Removing a column
ALTER TABLE PREMTARR.CUSTOMER
DROP COLUMN COMM_RATE
You lose all the data in the column as well. Adding, changing and dropping tables is not something
the company wants to do a lot of with its day-to-day data. That is why it is important to design it
properly. However sometimes changes need to be made. Also, you will be working in the developing
side of the business and you will need to add, change and delete tables all the time.
It is good idea to do a SELECT * to look at what the table contains and what columns exist now.
Insert data into table, but use your own name.
INSERT INTO PREMTARR.CUSTOMER VALUES
('100', 'LAST', 'FIRST','100 STREET','TORONTO', 'ON', 'M9W1A4', 5000, 1234.56, '6')
Insert these two rows into SALESREP
INSERT INTO PREMTARR.SALESREP VALUES ('6', 'RON TARR')
INSERT INTO PREMTARR.SALESREP VALUES ('99','RON TARR99')
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DATA
Adding data to a table
Insert data into table, but use your own name.
INSERT INTO PREMTARR.CUSTOMER VALUES
('100', 'LAST', 'FIRST','100 STREET','TORONTO', 'ON', 'M9W1A4', 5000, 1234.56, '6')
Notice
1. That the first value is in single quotes. This is because the first column was defined as character
data. Just like any other language character data is in quotes. For SQL data is in single quotes. Only
alternate names for columns in the select clause has double quotes.
2. The values must be in the same order and data type as the table.
3. If the column allows NULL, then NULL must be used as in the example below.
INSERT INTO PREMTARR.CUSTOMER VALUES
('100', 'LAST', 'FIRST', NULL,'TORONTO', NULL, 'M9W1A4', 5000, 1234.56, '6')
NULL is not a character value and does not need quotes. This example will not work for 2 reasons
1) A primary key was defined and we already used ‘100’
2) Last name and province were defined as not allowing NULL values.
Insert these two rows into SALESREP
INSERT INTO PREMTARR.SALESREP VALUES ('6', 'RON TARR')
INSERT INTO PREMTARR.SALESREP VALUES ('99','RON TARR99')
Deleting data from the table
DELETE FROM PREMTARR.CUSTOMER  Since there was no condition all the rows were deleted
Insert the row back into CUSTOMER
Insert it again. Note the error message. That is a check being done by the DBMS that you don't have
to program to ensure the integrity of the data.
Insert another row, so that you have 2 rows in the table CUSTOMER
Delete only one of the 2 rows by adding a condition.
DELETE
FROM PREMTARR.CUSTOMER
WHERE
CUSTOMER_NUMBER = '100'
Changing data in a table
UPDATE
PREMTARR.CUSTOMER
SET
STREET
= 'UPDATED100'
WHERE
CUSTOMER_NUMBER ='100'
If there is not a WHERE condition then all rows will be updated to the same address.
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Working with data
Now insert the following using a new PK and FK value
INSERT INTO PREMTARR.CUSTOMER VALUES
('300', '300LAST', '300FIRST','300 STREET','TORONTO', 'ON', 'M9W1A4', 3000, 1234.56, '1')
An error occurs as follows:
 Operation not allowed by referential constraint CUST_SALES_REP_FK in -- etc
This is another check done by the DBMS
Now add a column to the SALESREP table called COMM_RATE using this code
ALTER TABLE PREMTARR.CUSTOMER
ADD COLUMN
COMM_RATE
DECIMAL (3,2)
Oops -- it was added to the wrong table. Leave it there and we will fix it later. Now add it to the
correct table
ALTER TABLE PREMTARR.SALESREP
ADD COLUMN
COMM_RATE
DECIMAL (3,2)
Now apply a constraint on the new field to allow only specified values. The constraint is called
CHECK
ALTER TABLE PREMTARR.SALESREP
ADD CONSTRAINT PREMTARR.COMM_RATE
CHECK (COMM_RATE IN (0.05, 0.06, 0.07) )
Add a UNIQUE constraint
ALTER TABLE PREMTARR.SALESREP
ADD CONSTRAINT PREMTARR.SALES_REP_NAME
UNIQUE (SALES_REP_NUMBER)
Test the constraints. Do a select so that you know what data you have already and insert more
testing the CHECK and UNIQUE constraints.
INSERT INTO PREMTARR.SALESREP VALUES ('7', '7RON TARR',.7)
Did it work?
INSERT INTO PREMTARR.SALESREP VALUES ('98','RON TARR99')
Did it work and why if not why?
INSERT INTO PREMTARR.SALESREP VALUES ('98','RON TARR99', .06)
Did this correct the problem above?
INSERT INTO PREMTARR.SALESREP VALUES ('98','RON TARR98', .06)
Finally ---- You have tested the keys
You have modified the table by adding columns and constraints, now remove the wrong column
added to the customer table
ALTER TABLE PREMTARR.CUSTOMER
DROP COLUMN COMM_RATE
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Drop a constraint. I have chosen the FK on CUSTOMER
ALTER TABLE PREMTARR.CUSTOMER  alter the table
DROP FOREIGN KEY
 what action
PREMTARR.CUST_SALES_REP_FK  apply to what or name the constraint to drop
Up to this point in time we have done reports from 1 table only. Suppose you wanted to produce an
invoice. You would need data from CUSTOMER, INVOICE, INVOICELINE, PRODUCT and maybe
several other tables, depending upon the complexity of the system (Tax, sales_reps, shipping data
etc)
For this example you will need to cut and paste the following commands to create a table
CREATE TABLE PREMTARR.PRODUCT
(PID
NUMERIC (2),
PDESC
CHAR (15) NOT NULL,
QOH
NUMERIC (4)
)
CREATE TABLE PREMTARR.INVOICE
(INVID
NUMERIC (4),
CID
CHAR (3)
)
CREATE TABLE PREMTARR.INVOICELINE
(INVID
NUMERIC (4),
PID
NUMERIC (2),
QOO
NUMERIC (2)
)
DATA - adding new data to a table uses the INSERT statement
Now insert some data
INSERT INTO PREMTARR.CUSTOMER VALUES
('100', 'LAST', 'FIRST','100 STREET','TORONTO', 'ON', 'M9W1A4', 5000, 1234.56, '6')
INSERT INTO PREMTARR.INVOICE VALUES (1111, '100')
INSERT INTO PREMTARR.INVOICE VALUES (2222, '100')
INSERT INTO PREMTARR.PRODUCT VALUES (11, 'PRODUCT 11', 1011)
INSERT INTO PREMTARR.PRODUCT VALUES (12, 'PRODUCT 12', 1212)
INSERT INTO PREMTARR.PRODUCT VALUES (13, 'PRODUCT 13', 25)
INSERT INTO PREMTARR.INVOICELINE VALUES (1111, 13, 2)
INSERT INTO PREMTARR.INVOICELINE VALUES (1111, 12, 12)
INSERT INTO PREMTARR.INVOICELINE VALUES (2222, 13, 12)
To retrieve data for an invoice you need information from many tables. If you ran this it would not look
like an invoice, because the data has not been re-arranged on an invoice form. However all the
required data will be selected and displayed.
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SELECT
PREMTARR.INVOICE.INVID,
PREMTARR.CUSTOMER.CUSTOMER_NUMBER,
PREMTARR.CUSTOMER.LAST_NAME,
PREMTARR.PRODUCT.PID,
PREMTARR.PRODUCT.PDESC,
PREMTARR.INVOICELINE.QOO,
PREMTARR.SALESREP.SALES_REP_NAME
FROM
PREMTARR.CUSTOMER, PREMTARR.INVOICE,PREMTARR.INVOICELINE,
PREMTARR.PRODUCT,PREMTARR.SALESREP
WHERE
PREMTARR.CUSTOMER.CUSTOMER_NUMBER = PREMTARR.INVOICE.CID
AND
PREMTARR.CUSTOMER.SALES_REP_NUMBER =
PREMTARR.SALESREP.SALES_REP_NUMBER
AND
PREMTARR.INVOICE.INVID = PREMTARR.INVOICELINE.INVID
AND
PREMTARR.INVOICELINE.PID = PREMTARR.PRODUCT.PID
ORDER BY PREMTARR.INVOICE.INVID
What does the SQL look like if I didn’t have to qualify every name with the collection as required by
AS400?
SELECT
I.INVID,
we qualify with the table tame when a column is in 2 tables to avoid ambiguity
CUSTOMER_NUMBER,
 no
ambiguity here
LAST_NAME,
P.PID,
P.PDESC,
QOO,
S.SALES_REP_NAME
FROM
CUSTOMER C,  the C is an alias name, so that the full name doesn’t need to be used
INVOICE
I,
INVOICELINE IL,
PRODUCT P,
SALESREP S
WHERE
C.CUSTOMER_NUMBER
= I.CID
AND
C.SALES_REP_NUMBER
= S.SALES_REP_NUMBER
AND
I.INVID
= IL.INVOICELINE.INVID
AND
IL.PID
= P.PID
ORDER BY I.INVID
VIEWS
Creating a view. A view is LIKE a table. It has a structure, but unlike a table it has no data. The data
that a view appears to have is loaded at run time.
Views are used to
1 - provide a form of security in that only part or parts of tables will be shown and the user getes
permission to access those parts and not permission on the tables.
2 - It can simplify so that users that have some SQL ability can do reports. For example a complicated
join and other where conditions could be used in a view, but the user then needs only to use simple
SQL
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Examples follow.
Creating the VIEW that will be called CR and gets the data from 2 tables
CREATE VIEW PREMTARR.CR <== name the view
(CUSTOMER_NUMBER, LAST_NAME, CREDIT_LIMIT,SALES_REP_NAME)<== Note 1 below
AS SELECT PREMTARR.CUSTOMER.CUSTOMER_NUMBER, <== the columns to show
PREMTARR.CUSTOMER.LAST_NAME,
PREMTARR.CUSTOMER.CREDIT_LIMIT,
PREMTARR.SALESREP.SALES_REP_NAME
FROM
PREMTARR.CUSTOMER,
<== the tables where data exists
PREMTARR.SALESREP
WHERE
PREMTARR.CUSTOMER.SALES_REP_NUMBER =
PREMTARR.SALESREP.SALES_REP_NUMBER <== the join condition
Note 1. On the AS400 it tells you what the column names in the CREATE VIEW will be. It took the
names from the underlying tables. If you wanted you could have given the columns a different name
such as CID instead of CUSTOMER_NUMBER. You would have specified them on that line.
Query using the view is like any other table. You can see it has 4 columns so you can SELECT as
though it was a table. At the time the SELECT is run the underlying data is retrieved from the original
tables.
Try this.
SELECT
*
FROM PREMTARR.CR
SELECT
FROM
LAST_NAME
PREMTARR.CR
SELECT
FROM
WHERE
LAST_NAME
PREMTARR.CR
CUSTOMER_NUMBER > 'LZ'
Notice how easy it was to get information. No join was needed.
Notice that if a user is given permission to use CR then, they won't have access to other information
about the customer that is not vital to their job. For example the clerk in payroll may get to see all
employees data, except the executive salaries. Therefore the view will be created with a WHERE
statement that excludes executive employees.
A manager in Computer Studies may be able to see students and faculty in their department and not
in any other department. This is the security aspect.
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