SQL. Agenda. Where you want to go Today for database access. What is SQL

Transcription

1 SQL Where you want to go Today for database access What is SQL Agenda 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

2 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 Query Data definition Data manipulation Data 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

3 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.

4 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.

5 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.

6 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.

7 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

8 DB2/400 Query Manager and SQL Development Kit SQL/400 Interactive SQL RUNSQLSTM command SQL precompilers The languages supporting embedded SQL statements: ILE C/400 COBOL/400, ILE COBOL/400 FORTRAN/400 AS/400 PL/I RPG/400 (III), ILE RPG/400 SQL/400 Query Manager Query Management AS/400 SQL Execution Interactive SQL STRSQL SQL Statement Processor RUNSQLSTM Query Manager STRQM Work with queries, report forms, tables, query manager profiles

9 SQL Execution (continued) SQL embedded in HLL programs Static SQL SQL statement type and structure known at compile time Dynamic SQL SQL statement and structure created at run time Resource 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

10 SQL/400 Statements Data Definition CREATE or DROP Database or Collection Table (define rows and columns) View (column projection and ordering) Index (row ordering) Procedure (External Procedure) Package (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)

11 SQL/400 Statements (cont.) Remote Data Access CONNECT SET CONNECTION RELEASE DISCONNECT Data Access Control GRANT or REVOKE Table 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)

12 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 2 F JOE 5 M JON 7 M DON 5 M ANN 8 F

13 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 % = any number of characters _ = 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

14 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 SELECTname, number, position FROM Empl WHERE sex = 'M' AND (salary * 12) > ORDER BY name Name Number Position JOE 35 5 JON 30 SELECTname, number, position FROM Empl ORDER BY 2 Name Number Position JON 30 7 JOE 35

15 SELECT GROUP BY example SELECTposition, SUM(salary), COUNT(*) FROM Empl GROUP BY position ORDER BY position Position SUM(Salary) Count SELECT WHERE Join example Number Name Position Sex Salary 10 AMY 2 F JOE 5 M JON 7 M DON 5 M ANN 8 F 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 2 Operator JOE 5 Programmer DON 5 Programmer JON 7 Manager ANN 8 Analyst

16 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

17 One Row at a time: INSERT Statement 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 Logical Expressions String Manipulation Date/Time functions Data format manipulation Other DB/2 functions

18 Column Functions AVG Average of a numeric column SUM Adds 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 MAX

19 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, NOW, QUARTER, WEEK... Data format manipulation (11) DECIMAL, 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 '

20 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

21 Embedded SQL New source type SQLRPG (RPGIII), SQLRPGLE (RPGIV) SQL uses a precompiler (option 14 in PDM) CRTSQLRPG (RPGIII), CRTSQLRPGI (RPGIV) User Source File SQL Precompiler Modified Source File Language Compiler Program Syntax Checking X-ref host variables SQL statements to call Access paths to use Processed SQL Stmts 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 can 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

22 RPG syntax for embedded SQL /EXEC SQL in pos 7 indicates beginning of SQL statement SQL statement begins in pos of this or following lines /END-EXEC in pos 7 indicates end of SQL statement pos 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 do not use the RPGIV field prefix

23 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 if 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 an error will occur when converting a 4 byte year to these formats when the date is outside of this range.

24 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

25 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

26 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 C/END-EXEC 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 Setup data structure RECDS to receive data Put SQL statements into variable SELECTSTMT

27 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) PROGRAM: PGMB C *ENTRY PLIST C PARM FUNCTION C PARM EMPL_NAME C PARM EMPL_NBR

28 Advanced SQL SQL Communications Area (SQLCA) automatically placed into RPG program by SQL precompiler contains feedback information SQLCODE or SQLSTATE SQL error codes (SQLCOD) 0 = statement executed successfully +n = executed but with warning +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 retrieving records sequentially by key (selected columns) RPG IV retrieving records sequentially by key (all columns) updating records sequentially retrieving a set of records within a major key retrieving individual records by primary key retrieving individual records by RRN Tests were run under V3R6

29 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 Query Optimizer selects most efficient valid technique for the type of query being processed Start Database Monitor - STRDBMON (V3R6) Print SQL Information command - PRTSQLINF Query Debug Messages STRDBG UPDPROD(*YES)

30 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 access plan (access path to be used/created) estimated run time parameters used in the SQL precompile

31 Query Optimizer TOP 10 Debug Message List CPI Access path built for file CPI432F - Access path suggestion for file CPI Temporary file built for file CPI Access path built for file CPI The OS/400 Query access plan has been rebuilt CPI Arrival sequence access was used for file CPI432A - Query optimizer timed out for file CPI432E - Selection fields mapped to different attributes CPI Temporary result file built for query CPI 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

32 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: run time record selection, file selection, sorting criteria run time substitution variables ad-hoc programming (file conversions) embedded SQL ODBC connection

33 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 Manuals Bibliography SC DB2 for OS/400 SQL Programming V3R2 SC DB2 for OS/400 SQL Reference V3R2 SC 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

34 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