SQL in RPG

Transform Your RPG with the Power You Deserve!

Goals

● Create RPG source that can contain SQL

● Compile these sources as programs or modules

● Learn and use techniques to handle data between SQL and RPG variables

● Use some awesome SQL features to power up our RPG

SQLRPGLE

● Way too many letters● A new type of data source, totally backwards compatible● Turn any source into an source● Only adds features, takes none away● Compiles with a different command● Allows

CRTSQLRPGI

● Use this to compile your source● Same outcome, but this runs a SQL precompile first

○ Lets you know if any of your SQL will break○ Checks to make sure tables exist

● Replace both and ○ This new command takes in ObjType(*PGM) or ObjType(*Module)

● If you’re using RDi (you should!) you don’t even have to think about it

Getting started

● Create a program exactly as you normally would, but of type ○ No F-Specs needed!

● Create variables LIKE your tables

● “EXEC SQL …” to run any SQL you want○ Test everything out in Run SQL Scripts and then copy it over!○ Many strategies to getting the most out of embedded SQL

● Within SQL, use colons to access RPG variables○ “… WHERE id = :id ”

CRTSQLRPGI

CRTSQLRPGI OBJ(&O/&N) SRCFILE(&L/&F) SRCMBR(&N) REPLACE(&R)

CRTSQLMOD

CRTSQLRPGI OBJ(&O/&N) SRCFILE(&L/&F) SRCMBR(&N) OBJTYPE(*MODULE) REPLACE(&R)

Many other options you may or may not want

Before we get started

● SQL Options○ Whatever you need to do with commitment control

● Many of the following strategies do not exactly translate to Run SQL Scripts○ For each, I will show which parts can go back and forth for testing

● SQL to create tables, etc. generally won’t apply here○ Instead we’ll be looking at various ways so look through and update data on existing tables

Commitment Control

● Make all the database changes you want

● Nothing happens until a “commit”

● If one statement fails towards the end, you can avoid committing anything

● More often than not I turn off commitment control

EXEC SQL SET OPTION commit=*chg;or

EXEC SQL SET OPTION commit=*none;

Embedded SQL Strategies

External Name

● Create Data Structures exactly like your table● Can be a single data structure, or an array● It will have fields for all your different columns● Must use system name for the table, not the SQL name

Template variables

● Since we don’t have F-specs, we need standalone variables for everything● Create a template DS that is like a table● It will take up no memory itself, but can be used to define variables when

needed

Embedded SQL Strategies

Select Into

Select Into

● Get some data from a table, and put it into a variable● You can use “SELECT *” and the whole data structure● Be sure you’re only getting one record back

Select Into

● Use a template variable if you just need some fields

Select Into

● More usefully, the WHERE clause can also use RPG variables

Select Into - Testing in Run SQL Scripts

● Put together your SELECT in Run SQL Scripts● Leave out the “INTO” - no RPG variables allowed● Try running it and make sure you’re getting the data you expect● Make sure you’re getting one record back with the type of data you want

Select Into - Testing in Run SQL Scripts

Select Into Summary

● Use any crazy query you can come up with

● Utilize joins, Built-In SQL functions, and other SQL features

● Take in input or use any RPG variables to help find your data

● Finally, get that data you retrieved and put it into a new RPG variable

Embedded SQL Strategies

Insert

Insert with RPG variables

● Use RPG variables as we saw, but on an insert statement● Use a whole data structure again to make things nicer

Insert with RPG variables

● Specify column names if you want to use the auto-generate, auto-increment features

● Bulk insert a data structure array

● Wrap the values you’re inserting in SQL functions when you need

● Easy to test in Run SQL Scripts, just replace RPG variables with sample data

Embedded SQL Strategies

Update

Update with RPG variables

● Use RPG variables to filter like SELECT INTO

● Use RPG variables to write data like INSERT

● Still using SQL functions wherever you want

● Easy to test in Run SQL Scripts, just replace RPG variables with sample data

Embedded SQL Strategies

Cursors

Cursors

● Open a cursor with a SELECT statement with many rows● Loop through the cursor● Similar use and concept as and but with increased flexibility

● Fill a data structure array with all your rowsOR

● Fill a single data structure to be used just within each loop

Cursors

● Every cursor is declared with a name

● Every cursor must be opened and closed

Cursors - updating

● Must include FOR UPDATE OF

● UPDATE without a WHERE clause

Cursors without a loop

● Instead of looping, you can fetch all your rows at once

● Declare your data structure with a dimension at the beginning

● Declaring, opening, and closing the cursor still necessary

● Fetch the number of rows equal to that array size instead of a loop

Cursors - Testing in Run SQL Scripts

● Cursors are totally valid in Run SQL Scripts, however RPG loops are not

● The most important thing to test beforehand with cursors is your select statement○ Run SQL Scripts is perfect for testing SELECTs!

● Make sure you get exactly the rows you want to be looping through

● The rest of your cursor logic will largely be RPG, or should be broken down further for testing

Error Handling

SQLSTATE

● sqlstate is a variable you don’t have to define● char(5)

○ But made up of numbers

● Always exists within any SQL compiled RPG● You can check its value at any time● After running a statement, the value will update based on success

SQLSTATE

● ‘00XXX’ - Success

● ‘01XXX’ - Warning

● ‘02XXX’ - No data found to act upon

● Anything greater is an error○ Google!

SQLSTATE

● After any EXEC SQL, you can check the value of sqlstate and throw an error if necessary

● Easy to leave loop or give a known message for ‘02XXX’

● Anything higher is probably not anticipated, so logging the sqlstate in some way is a good idea

SQLSTATE

Use SQLSTATE to leave Cursor

SQLCODE

● Another variable you can use anywhere, similar to sqlstate● Different values with different meanings, but generally map to each other● SQLCODE is numeric● Error if less than 0● Perfect if 0● Warning if greater than 0

○ 100 = No data to act upon

● I tend to use sqlstate but they both do the job

Get the most out of SQL

Set

● Simply setting a variable, but with the power of SQL● Great for handling timestamps● Great for using SQL functions when no data is needed

Set

Whenever I need Regex, I go straight for SQL

Use handy SQL functions - IBM is always creating more!

Diagnostics

Date and Time

● Create a date, time, or timestamp● OR use

○ CURRENT TIMESTAMP○ CURRENT DATE○ CURRENT TIME

Date and Time

● YEAR(:timestamp)● MONTH(:timestamp)● DAY(:timestamp)● HOUR(:timestamp)● MINUTE(:timestamp)● SECOND(:timestamp)

Date and Time

● Easily subtract dates and times

Aggregations

● COUNT(column_name)○ Count how many rows were returned in any select statement

● SUM(column_name)○ Sum up a numeric column, only on the rows that you select

● These are aggregate functions○ They can’t be combined with selecting row data*

● They can be combined with each other, as long as they are aggregating the same rows

Aggregations

Summary

● Create and compile your sources as - no downsides!● Write powerful SQL in , then bring that into your RPG code● Create RPG variables based on a table

○ No F-specs!

● Use many different strategies to use SQL with RPG variables● Try out all the awesome new features SQL provides us, find new features

every day

IBM is putting a crazy amount of effort into this so we want to keep up!