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SQL
Where you want to go Today
for database access
Agenda
What is SQL
„ AS/400 database query tools
„ AS/400 SQL/Query products
„ SQL Execution
„ SQL Statements / Examples
„ Subqueries
„ Embedded SQL / Examples
„ Advanced SQL
„ SQL Performance / Tuning
„ Future Enhancements to SQL
„ Conclusion
„
1
What is SQL
„
SQL - Structured Query Language
–A
standardized language for defining and
manipulating data in a relational database.
– English keyword oriented
– A tool for the application development environment
zQuery
zData definition
zData manipulation
zData Control
– Set-At-A-Time processing
– SQL is not an end user query product
SQL Openness - Standards
„
SQL in DB2/400 has very high standards
compliance
– Entry
level of 1992 ANSI, ISO, and FIPS SQL
Standard
„
X/Open SQL Call Level Interface (CLI)
provides full compliance with level 1 of
Microsoft's ODBC support plus many of
level 2 functions.
– Available
only in the ILE environment
2
AS/400 database query tools
Open Query File (OPNQRYF) command
„ Query/400
„ SQL/400 Query Manager
„ SQL/400
„
– Interactive
„
SQL, Statement Processor
SQL/400 run time support
– SQL
Parser, API's, commands
X/Open SQL Call Level Interface
„ OS/400 Query Management
„
Open Query File (OPNQRYF)
command
„
This is a programming command that can
be used with a high-level language program.
It acts as a filter between the program and
the database, so that the program receives
only those records that meet the criteria
specified in the OPNQRYF command. It is
not built on the SQL/400 language.
3
Query/400
This tool allows easy reporting on database
information. It is not built on the SQL/400
language.
„ One feature unique to Query/400 is the
option of merging data into OfficeVision/400
documents.
„
SQL/400 Query Manager
„
This tool allows easy reporting on database
information. It is the interface for using the
SQL/400 language and OS/400 Query
Management. SQL/400 Query Manager
provides three integrated interfaces for the
creation and maintenance of queries, report
forms, and database tables.
4
SQL/400
Programmers use the SQL/400 language to
query and manipulate data in a database.
Most SQL functions can be performed either
interactively or in application programs
written in a high-level programming
language.
„ Interactive SQL can also be used by
programmers to test SQL statements.
„ The SQL statement processor allows you to
run a series of SQL statements stored in a
source file.
„
SQL/400 run-time support
SQL run-time parses SQL statements and
runs any SQL statements. This support is
part of the Operating System (OS/400)
licensed program.
„ It allows applications that contain SQL
statements to be run on systems where the
SQL Development Kit is not installed.
„
5
X/Open SQL Call Level Interface
Allows any of the ILE languages to access
SQL functions directly through procedure
calls to a service program provided by the
system. Using this interface, one can
perform all the SQL functions without the
need for a precompile.
„ It is ideally suited for a client-server
environment, in which the target database is
not known when the application is built.
„
OS/400 Query Management CPI
„
The Query Management Communications
Programming Interface lets users access
information on SAA-compliant relational
databases and control how this data
appears when formatted into a report. This
standard is also found on other SAA
platforms such as PC's and Mainframes.
6
DB2/400 Database Manager
(Included in OS/400 V3Rx)
„
Open Query File (OPNQRYF) command
– Not
„
built on the SQL/400 language
SQL Parser and run time support
– Allows
SQL programs to be ported and run on AS/400's
not containing SQL kit
– Commands available to create a single runnable SQL
statement
„
SQL API's
– QSQPRCED
- executes SQL packaged statements
– QSQCHKS - checks syntax of SQL statements
„
X/Open SQL Call Level Interface (V3R2)
– ODBC
support
Query/400
Separate feature not included in OS/400
„ Same basic interface as the System/36
Query product
„
7
DB2/400 Query Manager and SQL
SQL/400 Development Kit
z
– Interactive
SQL
– RUNSQLSTM command
zSQL precompilers
zThe languages supporting embedded SQL statements:
zILE C/400
zCOBOL/400, ILE COBOL/400
zFORTRAN/400
zAS/400 PL/I
zRPG/400 (III), ILE RPG/400
zSQL/400 Query Manager
zQuery Management
AS/400 SQL Execution
„
Interactive SQL
– STRSQL
„
SQL Statement Processor
– RUNSQLSTM
„
Query Manager
– STRQM
Work with queries, report forms, tables, query
manager profiles
z
8
SQL Execution (continued)
„
SQL embedded in HLL programs
– Static
SQL
zSQL statement type and structure known at compile
time
– Dynamic SQL
zSQL statement and structure created at run time
zResource intensive
„
SQL run-time support
– SQL
Parser, SQL API's
– CRTQMQRY, STRQMQRY commands
– Default source file - QQMQRYSRC
– New object type - QMQRY
„
X/Open SQL CLI
Database Terminology Table
SYSTEM TERMS
AS/400 System Name
Library
Physical File
Logical File
Record
Field Name
Data Dictionary
SQL Package
SQL TERMS
Database Name
Collection
Table
View
Row
Column Name
Catalog
Package
9
SQL/400 Statements
„
Data Definition
– CREATE
or DROP
zDatabase or Collection
zTable (define rows and columns)
zView (column projection and ordering)
zIndex (row ordering)
zProcedure (External Procedure)
zPackage (DRDA Remote Support)
– LABEL/COMMENT ON (table/column text)
– ALTER TABLE
SQL/400 Statements (cont.)
„
Data Manipulation
– INSERT
INTO (rows into tables)
– DELETE (rows from tables)
– UPDATE (table rows)
– SELECT (rows from tables)
– OPEN (opens the cursor)
– DECLARE CURSOR (set pointer)
– FETCH (retrieve columns)
– CLOSE (closes the cursor)
10
SQL/400 Statements (cont.)
„
Remote Data Access
– CONNECT
– SET
CONNECTION
– RELEASE
– DISCONNECT
„
Data Access Control
– GRANT
or REVOKE
zTable or Package
„
Data Integrity
– COMMIT
– SET
TRANSACTION
– ROLLBACK
– LOCK TABLE
SQL/400 Statements (cont.)
„
Dynamic SQL
– DESCRIBE
(retrieves info on PREPARE)
– EXECUTE (runs the prepared SQL statement)
– EXECUTE IMMEDIATE (prepares and
executes an SQL statement)
– PREPARE (create SQL statement from string)
11
SQL/400 Statements (cont.)
„
Miscellaneous
– BEGIN/END
DECLARE SECTION (not used in
RPG)
– CALL (call external procedure)
– DECLARE (Cursor, Procedure, Statement,
Variable)
– INCLUDE (insert data set into SQL statements)
– SET OPTION (SQL options)
– SET RESULT SETS (data from CA/400)
– WHENEVER (exception handling)
SELECT Statement & Clauses
SELECT
(columns, *, or expressions)
FROM
(tables or views)
WHERE
(row selection criteria)
GROUP BY
(columns)
HAVING
(GROUP BY selection criteria)
ORDER BY
(columns)
SELECT *
FROM
empl
Number
Name
Position
Sex
Salary
10
AMY
35
JOE
2
F
1200
5
M
1000
30
20
JON
7
M
1500
DON
5
M
1150
25
ANN
8
F
12
SELECT Statement keywords
„
Keywords in WHERE clause:
– Greater
than (or =), Less than (or =), Equal
– Not greater, Not less, Not equal
– AND, OR, NOT
– Range - inclusive constant range (BETWEEN,
NOT BETWEEN)
– Values - list of constant values (IN, NOT IN)
– Pattern matching (LIKE, NOT LIKE) with wild
cards
z% = any number of characters
z_ = exactly 1 character
SELECT Where Example
Columns can be reordered
„ Selection criteria can be applied
„
SELECT Name, Number
From Empl
Where Position = 5
Name
Number
JOE
35
DON
20
13
SELECT Where example
SELECT name, position
FROM Empl
WHERE position BETWEEN 5 AND 7
Name
Position
JOE
5
JON
7
DON
SELECT name, number
FROM Empl
WHERE name LIKE 'A%'
Name
Number
AMY
10
ANN
SELECT ORDER BY example
SELECT name, number, position
FROM Empl
WHERE sex = 'M' AND (salary * 12) > 12000
ORDER BY name
Name
Number
Position
JOE
35
JON
30
SELECT name, number, position
FROM Empl
Name
ORDER BY 2
JON
JOE
5
Number
Position
30
7
35
14
SELECT GROUP BY example
SELECT position, SUM(salary), COUNT(*)
FROM Empl
GROUP BY position
ORDER BY position
Position
SUM(Salary)
Count
2
1200
1
5
2150
2
7
1500
1
8
1500
1
SELECT WHERE Join example
Number
Name
Position
Sex
Salary
10
35
30
20
25
AMY
JOE
JON
DON
ANN
2
5
7
5
8
F
M
M
M
F
1200
1000
1500
1150
1500
Position
Description
2
Operator
5
Programmer
7
Manager
8
Analyst
SELECT name, EMPL.position, description
FROM Empl, Job
WHERE Empl.position = Job.position
Name
Position
Description
AMY
JOE
DON
2
5
5
Operator
Programmer
Programmer
JON
ANN
7
8
Manager
Analyst
15
Joining Tables
WHERE clause used to specify join
conditions
„ Join columns must have compatible
attributes
„
– number
to number, character to character
– padding and truncation
Join conditions (=, ~=, <>, <, ~<, <=, >, ~>,
>=)
„ SELECT clause can contain:
„
– columns
from any joined table
UPDATE Statement
SQL is a SET-AT-A-TIME language
„ Give all programmers a 50% salary increase
„
UPDATE Empl
SET salary = salary + (salary * 0.50)
WHERE position = 5
16
INSERT Statement
One Row at a time:
INSERT INTO Empl
(name, number, position, salary, sex)
VALUES ('PAT',11,2,1300,'F')
Multiple Rows at one time:
INSERT INTO Empl
SELECT number, name, position, salary, sex
FROM Emplnew
WHERE position = 9
SQL 'Built-in' Functions
Can be used anywhere expressions are used
„ Column Functions
„
– Applies
„
to an entire column (grouping of records)
Scalar Functions
– Applies
to a single value rather than a set of records
Mathmatical functions
z Logical Expressions
z String Manipulation
z Date/Time functions
z Data format manipulation
z Other DB/2 functions
z
17
„
Column Functions
AVG
– Average
„
SUM
– Adds
„
of a numeric column
numeric column
MAX
– Maximum
„
value of a numeric or character
MIN
– Minimum
value of numeric or character
„
VAR
„
Variance between the sum of 2 numbers
„
COUNT
– Counts
the number of rows
Column Functions examples
SELECT COUNT (*)
FROM Empl
COUNT
6
SELECT MAX(salary), MIN(salary)
FROM Empl
MIN
1000
MAX
1500
18
Scalar Functions
„
Mathmatical Functions (23)
– COS,
„
SIN, COT, TAN, LOG, SQRT...
Logical Expressions (3)
– LAND,
„
LOR, XOR
String Manipulation(17)
– LOCATE,
„
TRIM, STRIP, SUBSTR, TRANSLATE...
Date/Time functions (19)
– DAYOFYEAR,
„
Data format manipulation (11)
– DECIMAL,
„
NOW, QUARTER, WEEK...
FLOAT, HEX, INT, ZONED...
Other DB/2 Functions (4)
– NODE,
PARTITION, RRN
Scalar Function examples
Retrieve the number, name, and age of employees in
position 5
SELECT number, name, YEAR(CURRENT DATE - birthdate)
FROM Empl
WHERE position = '5'
Select records in project file with the word 'operation' in
the project name
SELECT *
FROM Project
WHERE SUBSTR(projname,1,10) = 'OPERATION '
19
Sub Queries
„
A subquery is a SELECT statement embedded in
the WHERE or HAVING clause of another SQL
query
– also
„
called inner query or nested query
Types of Subqueries
– returns
single value
– returns list of values
– Inner and Outer queries
Sub Query Example
„
Select maximum salary of employees in position 5
– returns
all records having the maximum salary in
position 5
SELECT * FROM empl
WHERE position = 5
and salary =
(SELECT MAX(salary)
FROM empl
WHERE position = 5)
Number
Name
Position
Sex
Salary
20
DON
5
M
1150
20
Embedded SQL
„
New source type
– SQLRPG
„
(RPGIII), SQLRPGLE (RPGIV)
SQL uses a precompiler (option 14 in PDM)
– CRTSQLRPG
User
Source
File
(RPGIII), CRTSQLRPGI (RPGIV)
SQL
Precompiler
Syntax Checking
X-ref host variables
SQL statements to call
Access paths to use
Modified
Source
File
Language
Compiler
Processed
SQL
Stmts
Program
Access
Plan
Placing SQL in RPG
SQL statements executed based on logic in program
„ SQL statements can only be placed in mainline or
subroutine of calculation specification
„
– cannot
be placed in total time processing
zcan call subroutine containing SQL statements
„
/COPY within RPG code
– copy
„
in source with SQL statements
SQL INCLUDE statement within SQL
– copy
in source with SQL and RPG IV
21
RPG syntax for embedded SQL
„
/EXEC SQL in pos 7 indicates beginning of SQL
statement
– SQL
statement begins in pos 17 - 80 of this or following
lines
„
/END-EXEC in pos 7 indicates end of SQL
statement
– pos
„
17 - 80 must be blank
Continuing the SQL statement
–+
in pos 7, pos 8 must be blank, statement can be in pos 9
- 80
Upper or lower case allowed in SQL code
„ Comment allowed in SQL statement by using an *
in pos 7
„
Host Variables
SQL Host Variable is an HLL variable used in an
embedded SQL statement
„ Defining Host variables
„
– all
host variables within an SQL statement must be preceded
by a colon (:)
– if the variable exists in more than one table (joined files), the
variable name must be prefixed with the table name (or
number) and a period
– host variables must be unique within the program
z
do not use the RPGIV field prefix
22
Host Variable restrictions
„
Any valid RPG/400 variable name can be used for a
host variable except for the following:
– host
variable names that begin with the characters 'SQ',
'SQL', 'RDI', 'DSN'. These names are reserved for the
database manager.
– indicator field names (*INxx)
– tables
– look-ahead fields
– named Constants
– RPG reserved date fields (UDATE, UDAY...)
– host variables passed to SQL that have also
been used in an RPG CALL/PARM function
zif field cannot be used in the result field of the PARM, it
cannot be a host variable
Variable restrictions (cont.)
„
Additional RPG IV restrictions:
– multiple
dimension arrays
– definitions requiring resolution of the field size (*SIZE,
*ELEM)
– date formats *JUL, *MDY, *DMY, *YMD can only
represent dates from 1940 - 2039.
zan error will occur when converting a 4 byte year to
these formats when the date is outside of this range.
23
Embedded SQL
Summarized column example
„
Returns total of column for selected rows
C/EXEC SQL
C+ SELECT SUM(THRS) INTO :HOURS
C+ FROM S#TIME
C+ WHERE CSTCOD = :CSTCOD AND
C+
PROJECT = :PROJECT AND
C+
TNOCH <> 'NC' AND
C+
TTASK <> 'INT'
C/END-EXEC
Embedded SQL
Select single row example
I
DS
1 50NBR
I
6 8 NAM
I
P 9 132EARN
C*
C
Z-ADD10
NBR
C/EXEC SQL
C+ SELECT number, name, salary
C+ INTO
:nbr, :nam, :earn
C+ FROM Empl
C+ WHERE number = :nbr
C/END-EXEC
NBR
NAM
EARN
10
AMY
1200
24
Embedded SQL
SELECT multiple rows
1. Define RPG fields
„ 2. Declare SQL Cursor
„ 3. Open Cursor
„ 4. Fetch next record
„ 5. Process record (UPDATE/INSERT, ect.)
„ 6. If last record go to Step 7, else: go to Step 4
„ 7. Close Cursor
„
Embedded SQL
SELECT multiple rows example
DRECDS E DS
EXTNAME(EMPL) OCCURS(10)
:
C/EXEC SQL
C+ DECLARE C1 FOR
C+ SELECT *
C+
FROM EMPL
C/END-EXEC
C/EXEC SQL
C+ OPEN C1
C/END-EXEC
* top of loop
C/EXEC SQL
C+ FETCH C1 FOR 10 ROWS
C+ INTO :RECDS
C/END-EXEC
* do something with record(s) and loop :
C/EXEC SQL
C+ CLOSE C1
C/END-EXEC
25
Embedded SQL
Update example
„
Updates a posted flag to a transaction file
after all records in batch are processed
C
EVAL
POSTED = 'Y'
C
EVAL
TODAY = UDATE
C*
C/EXEC SQL UPDATE TRANS
C+
SET POSTFLG = :POSTED
C+
WHERE TRNDATE = :TODAY
C/END-EXEC
Embedded SQL
Dynamic SQL statement
C/EXEC SQL
C+ PREPARE STMT4SQL FROM :SELECTSTMT
C/END-EXEC
C/EXEC SQL
C+ DECLARE NEXTREC CURSOR FOR STMT4SQL
C/END-EXEC
C/EXEC SQL
C+ OPEN NEXTREC
Setup data structure RECDS to receive data
C/END-EXEC
Put SQL statements into variable SELECTSTMT
C
DOU
EOF = *ON
C/EXEC SQL
C+ FETCH NEXTREC INTO :RECDS
C/END-EXEC
C
IF
SQLCOD <> 0
C
EVAL EOF = *ON
C
ELSE
C
EXSR LOADSF
C
ENDIF
C
ENDDO
C/EXEC SQL
C+ CLOSE NEXTREC
C/END-EXEC
26
Stored Procedures
Calling programs using SQL
PROGRAM: PGMA
C/EXEC SQL
C+ DECLARE PGMB PROCEDURE
*
* define fields being passed between programs
*
C+
( :action IN char(1),
C+
:name OUT char(3),
C+
:number IN char(5) )
*
* define location of program being called
*
C+
(External Name JUMPSTART/PGMB
C+
Language RPGLE
C+
Simple Call)
C/END-EXEC
:
C/EXEC SQL
C+ CALL PGMB(:function, :name, :nbr)
C/END-EXEC
Stored Procedures (cont.)
Program A contains the SQL parameters and
statements
„ Program B is a normal RPG program (no SQL
statements needed)
„
C
C
C
C
PROGRAM: PGMB
*ENTRY
PLIST
PARM
FUNCTION
PARM
EMPL_NAME
PARM
EMPL_NBR
27
Advanced SQL
„
SQL Communications Area (SQLCA)
– automatically
placed into RPG program by SQL precompiler
feedback information
– SQLCODE or SQLSTATE
– contains
„
SQL error codes (SQLCOD)
–0
= statement executed successfully
– +n = executed but with warning
z+100 'No Data Found'
– -n = Error occurred and statement did not run
– use SQLCA in HLL or with SQL WHENEVER
„
SQL Package
– normally
used to store access plan for remote query
Performance: SQL vs. RPG
„
SQL/400 beats RPG IV in two tests and very close in
several other tests:
– SQL
inserting large numbers of records
zretrieving records sequentially by key (selected columns)
– RPG IV
zretrieving records sequentially by key (all columns)
zupdating records sequentially
zretrieving a set of records within a major key
zretrieving individual records by primary key
zretrieving individual records by RRN
z
„
Tests were run under V3R6
28
SQL Performance tips
For high-volume sequential access, tune the
block size on the OVRDBF command
„ Use a blocked insert statement when adding
large numbers of new records
„ Use a multiple-row Fetch statement when
sequentially retrieving 10 or more records at
a time
„ Limit the number of columns you retrieve or
update
„
Tuning SQL
„
Predictive Query Governor
– system
„
predicts and expedites queries
Data Management and Query Optimizer
– Data
Management algorithms for index usage and row selection
Optimizer selects most efficient valid technique for the
type of query being processed
– Query
Start Database Monitor - STRDBMON (V3R6)
„ Print SQL Information command - PRTSQLINF
„ Query Debug Messages
„
z
STRDBG UPDPROD(*YES)
29
The Predictive Query Governor
„
„
„
„
„
„
Predictive - guesses how long the query will take before it starts
It works with all AS/400 Query products, not just SQL based
Can be used for tuning queries
Parameters for system and job
– specify how long of a query can be run
– setup the system to either prevent long queries or warn about
long queries.
WRKSYSVAL QQRYTIMLMT
– sets the value for everyone
CHGQRYA
– overrides the query time limit for a job
Print SQL Information command
(PRTSQLINF)
„
Can only be run against a saved access plan
– query
„
must have been executed or 'PREPARE' d
information about SQL statements embedded in a
program including:
– SQL
statements being executed
plan (access path to be used/created)
– estimated run time
– parameters used in the SQL precompile
– access
30
Query Optimizer
TOP 10 Debug Message List
„
„
„
„
„
„
„
„
„
„
CPI4321 - Access path built for file
CPI432F - Access path suggestion for file
CPI4324 - Temporary file built for file
CPI4322 - Access path built for file
CPI4323 - The OS/400 Query access plan has been rebuilt
CPI4329 - Arrival sequence access was used for file
CPI432A - Query optimizer timed out for file
CPI432E - Selection fields mapped to different attributes
CPI4325 - Temporary result file built for query
CPI4328 - Access path of file was used by query
Other SQL Topics
Dynamic SQL
„ Cursors
„
– serial,
scrolling
Using Null values
„ Date/Time Arithmatic
„ SQL Descriptor Areas (SQLDA)
„ Varying-list SELECT statement
„ Indicator Variables
„
31
Future enhancements - V4Rx
„
100% compliance with ANSI and ISO SQL
standards
– column-level
locking (V4R2)
– check constraints (V4R2)
– default User (V4R2)
– SQL-only stored procedures
– compound SQL
– Case and Cast expressions (V4R2)
DB2 Multisystem support and SMP support
„ New and improved X/Open API's
„ Java Database Connectivity (JBDC)
„
SQL Conclusion
„
English keyword oriented language
– easy
„
to learn
Greater programmer flexibility
– programming
interface into queries allows:
zrun time record selection, file selection,
sorting criteria
zrun time substitution variables
– ad-hoc programming (file conversions)
– embedded SQL
– ODBC connection
32
SQL/400 Conclusion (cont.)
„
Position for client/server applications
– Java,
ODBC/JDBC driver compatibility
Many tools available
„ Can be optimized and contolled
„ SQL/400 open to other platforms
„
– SAA-compliant
SQL statements are portable to
other SAA platforms
– SQL compiled objects can be run without
SQL/400 license
„
Provides table (file) creation function
Bibliography
„
Manuals
–
–
–
„
SC41-4611
SC41-4612
SC41-3806
DB2 for OS/400 SQL Programming V3R2
DB2 for OS/400 SQL Reference V3R2
DB2 for OS/400 SQL Call Level Interface V3R2
Articles
–
–
–
Dynamic SQL in RPG;Ed Oleson
DB2/400 Query Manager: The New AS/400 Query;Skip Marchesani;Sept/97
Using SQL on the AS/400;Skip Marchesani;Aug/97
33
Bibliography: Perodicals
–
–
–
–
–
–
–
SQL Minimalism; Thomas Stockwell; Midrange Computing; Apr/96
A quick introduction to SQL with RPG IV; Richard Rubin; News/400; Jan/97
An Introduction to SQL Subqueries; Ted Holt; Midrange Computing; Feb/96
OS/400 Tools to Speed Up SQL and OPNQRYF; Suzan Bestgen & Tom
Schreiber; News/400; Nov/96
SQL/400 vs. RPG IV: Which One's Faster?; Paul Conte; News/400; Sept/96
SQL/400 vs. DDS: Which Should You Use?; Paul Conte; News/400; Sept/96
DB2/400: Coming Attractions; Kent Milligan; News/400; Sept/97
34