Beginning SQL

5/27/2018 Beginning SQL

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SQLJumpstart

Mark Holm

Centerfield Technology


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Goals

Get you started with SQL

Show how SQL works with an existing

environment

Lay the groundwork for learning more

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Notes

V4R3 and higher syntax used in examples

Examples show only a small subset of what

can be done!

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Agenda

Explain why SQL is important

Compare SQL with traditional approaches

Data definition statements

Selecting data

Changing dataUsing SQL day to day

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Why SQL?

Simplifies cross platform development

SQL generation can be automated

Allows quick and flexible access to data

Operates on sets of data -> powerful

Official industry standard used by pervasive APIs

& products

ODBC/JDBC

Most query tools

Can perform better than traditional methods!

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Why SQL?

Business Intelligence

Query tools

Data manipulation & (some) data cleanup

Web sites & internet applications

Net.Data

JDBC

ERP applications SSA eBPCS

JDE One World

Mapics XA

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Tools

Interactive SQL (STRSQL)

Run SQL statement (RUNSQLSTM)

Operations Navigator

Query tools (ODBC)

And many others..

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Basic statements

Create Collection = CRTLIB

Create Table = CRTPF

Create View = CRTLF (no key)

Create Index = CRTLF (key)

Insert, Update, Delete = add, change, andremove records

Select = select records & columns to read

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Data definition (DDL)

Data definition statements create objects

Collections (libraries)

Tables (physical files)

Views (non-keyed logical files)

Indexes (keyed logical files)

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Create collection

Create collection = Create library

Example: CREATE COLLECTION HR

Objects created:Library named HR

Journal & journal receiver

Catalogs (e.g. SYSTABLES)

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DSPLIB of a newly created COLLECTION


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Create Table

Create table = Create physical file (CRTPF)

Objects created, etc.:Physical file

File automatically journaled to QSQJRN

Example: Create a table to hold employee

information

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Create table

CREATE TABLEHR/EMPLOYEE

(FIRST_NAME FOR COLUMNFNAME CHAR (20 ) NOT NULL,

LAST_NAME FOR COLUMN LNAME CHAR (30 ) NOT NULL,

EMPLOYEE_ID FOR COLUMN EMP_ID NUMERIC (6 , 0)NOT NULL WITH DEFAULT0,DEPARTMENT FOR COLUMN DEPT DECIMAL (3 , 0) NOT NULL WITH DEFAULT,

TITLE CHAR (30 ) NOT NULL WITH DEFAULT,

HIRE_DATE FOR COLUMN HDATE DATE NOT NULL)

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Tables vs. Physicals

Tables

Dirty data cantbe

inserted Marked as a table

Maximum 1 member

No maximum size

Default to reusedeleted rows

Table is automatically

journaled (collection)

Physical files

Dirty data can be

insertedNot an SQL object

No limit on members

Default is to cap size

Default to not reusedeleted records

File is not

automatically journaled

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Prompt for CREATE TABLE in Interactive SQL


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Create View

Create View = Create logical file (CRTLF)

Objects created:Logical file

No keyed access path

Example: View to format an employees first

& last name and identify employees hiredless than 2 years prior to today

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Create View

CREATE VIEWHR/NEWBIES (EMPLOYEE_NAME, DEPARTMENT, HIRE_DATE)AS

SELECT concat(concat(strip(last_name),','),strip(first_name)),

department,

hire_date

FROM HR/EMPLOYEE

WHERE (year(current date)-year(hire_date)) < 2

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DSPFD of a newly created VIEW


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View uses

Subset columns to users or applications

Create new columns for users or

applications

Subset the rows returned (hide data)

Join tables together

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Views vs. Logical files

View

Looks like logical file

Never has an access

path (index)

Powerful data

manipulation

Slower OPEN time

Views can reference

views

One member

Logical File

Is a logical file

Can be keyed or non-

keyed Basic data

manipulation

Faster OPEN time

Logical files can notreference LFs

Many members

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Create Index

Create Index = CRTLF (keyed logical)

Objects created:Logical file

Physical access path (index)

Created to improve performance -- not for

functionExample: Create an index over the

employee identifier

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Create Index

CREATE UNIQUE INDEXHR/EMPIDIX

ONHR/EMPLOYEE(EMPLOYEE_ID ASC)

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Indexes vs. Keyed logical files

Index

Looks like logical file

Powerful datamanipulation

Not usable as file

One member

Logical file

Is a logical file

Basic datamanipulation

Like a normal file

Many members

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Deleting objects

Done with a DROP statement

DROP TABLE

DROP VIEW

DROP INDEX

By default these statements drop dependent

objects unlike CL commands (e.g. you cantdelete a PF via DLTF if there are dependent

logical files)

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Data Manipulation (DML)

Insert- add rows to a table

Update- update column values in a table's

rows

Delete- delete rows in a table

Select - retrieve rows from one or more

tables

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Insert

Insert = add a new row (record)

Works just like HLL verbs

Example: Add a couple of employees to our

table in the human resources library

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Insert

INSERT INTOHR/EMPLOYEE

(FIRST_NAME, LAST_NAME, EMPLOYEE_ID,

DEPARTMENT, TITLE, HIRE_DATE)

VALUES ('Joe', 'Jones', 4793, 522, Hotshot Programmer', '1998-01-16')

INSERT INTOHR/EMPLOYEE

VALUES ('Jane', Smith', 3290, 712, Psychic Business Planner', '1999-12-01')

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Update

Update = change data in existing row

Works just like HLL verbs

Example: Give a 20% raise to one our star

employees

UPDATEHR/EMPLOYEESETSalary = Salary * 1.2

WHERE Employee_id = 5228

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Delete

Delete = Remove one or more rows

Example: Fire the human resources

department

DELETEFROMHR/EMPLOYEE

WHERE Department = 108

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Select

Select statement is the most complex and

powerful SQL statement

If you know how to write good selectstatements you are well on your way to

mastering the language

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Select

SELECT statement overview:

Select column(s)From table(s) or view(s)

Where selection criteria

Group Bygrouping columns

Having selection criteria for groups

Order Bysort order for result rows

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Select - example 1

Selects all columns (designated by *)

Selects data from the HR/EMPLOYEE table

Select all rows

SELECT*FROMHR/EMPLOYEE

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Select - example 2

Selects only two columns

Selects data from the HR/EMPLOYEE table

Select only rows with EMPID *EQ 556

SELECTLNAME, FNAME

FROMHR/EMPLOYEE

WHEREEMPID = 556

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Select - example 3

Selects two columns and calculates a third

called DISCPRICESelects data from the INVENTORY table

Selects parts in a defined range

SELECTShirtName, SKU,

PRICE*.8 ASDISCPRICE

FROM PRODLIB/INVENTORYWHERESYLE = HAWIAN ORCOLOR = PINK

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Select - example 4SELECT TERRITORY, SUM(SaleAmt),

AVG(SaleAmt), COUNT(*)

FROM PRODLIB/SALES

WHERE COUNTRY = USAGROUP BYTERRITORY

HAVING AVG(SaleAmt) > 10000.0

ORDER BY2 DESC

Rank sales in largest to smallest order summarized

by territory. Only look at sales in the United States

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Useful functions

Function Description

DIGITS(expression) Convert a numeric value to a character

string so it can be taken apart

DECIMAL(expression, precision, scale) Convert an expression to a packed decimal

number with a specific scale and precision

STRIP(string, type, character) Removes leading or trailing charactersfrom a string. Type can be B (both), L

(leading), or T (trailing). If you use

STRIP(string) both leading and trailing

blanks are removed.

LTRIM(string)

RTRIM(string)

Trim leading blanks from string

Trim trailing blanks from string

SUBSTR(string, start-position, length) Extracts part of a string beginning at thestart position and going for length

characters.

UPPER(string) Converts the string to UPPER CASE.

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More useful functions

Function Description

MONTH(date or timestamp) Returns the month of the year (1-12)

CURDATE()

CURTIME()

Returns todays date

Returns the current time

DAYOFWEEK(date or timestamp)QUARTER(date or timestamp)

WEEK(date or timestamp)

Returns a value from 1-7 representing theday

Returns 1-4 based on the years quarter

Returns 1-53 based on the week of the year

MIN(expression1, expression2,)

MAX(expression1, expression2,)

Return the minimum numeric value in list

Return the maximum numeric value in list

TANH(expression) Return the hyperbolic tangent of

expression (OK not really that useful!)

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Embedded SQL

Combines the power of SQL with HLLs

like RPG, COBOL, or C

All of the benefits of HLLs such asperformance, complex logic, and control

over data manipulation.with SQLs

capabilities for set at a time processing anddynamic selection

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Embedded SQL

The following statement is an example of

what an embedded statement looks like:

SELECT fname, lname, address

FROM employee

WHERE empid = :INPUTID

INPUTID is a host variable

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Embedded SQL

Embedded SQL programs are pre-compiled

and then compiled again

CRTSQLRPGI, CRTSQLCBLI

Pre-compiler identifies SQL with special

tags to indicate start and end of SQL

statement

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Source file

SQL pre-compiler

Temporary

Source file

HLL compiler Module or

Program

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Embedded SQL

C/Exec SQL

C+ Update Employee

C+ Set lname = :NewLN -- assign new last name

C+ Where empId = :EmployIdC/End-Exec

-----------------------------------------------------

Exec SQL

Update Employee

Set lname = :NewLNWhere empId = :EmployId

End-Exec

RPG

COBOL

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Tips

To start learning SQL use ISQL

or Operations Navigator

Create a sample collection and

tables

Add, change, and delete data

Try different select statements

and functions to get a feel for

the power of SQL

Read and try examples listed in

the book and internet resourcesin this presentation

Create tables with short and

long names

Put related SQL objects in the

same collection

If selecting a small amount of

data, create an index over thecolumns that most uniquely

identify the data

Be careful with UPDATE and

DELETE statements without a

WHERE clause

Use the AS clause to give

calculations understandable

names

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Other resources

Database Design and Programming for DB2/400 -book by Paul

Conte

SQL for Smarties- book by Joe Celko

SQL Tutorial- www.as400network.com

AS/400 DB2 web site at http://www.as400.ibm.com/db2/db2main.htm

Publications at http://publib.boulder.ibm.com/pubs/html/as400/

Our web site at http://www.centerfieldtechnology.com

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Summary

SQL is becoming increasingly important for

many reasons

Basic DDL is very similar to DDS

Power and flexibility come with the DML

statements -- in particular SELECT

There are many resources to help take youto the next level of understanding


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I hear and forget.I see and remember.

I do and I understand.

Kung Futse

551 B.C.

Beginning SQL

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