Stored procedures1 Stored procedures and functions Procedures and functions stored in the database

Stored procedures2 Layered models vs. stored procedures Ordinary layered model –user interface –functions –model –data Layered model with stored procedures –user interface –functions in DB –model + data in DB

Stored procedures3 Stored procedures / functions 313 Stored procedures /functions are –Named blocks of PL/SQL SQL DDL Assignments, if statements, loops, etc. –Syntax checked and compiled into p-code The p-code is stored in the database Stored procedures’ syntax –General syntax, page 314 –Example, page 315 Stored functions’ syntax –General syntax, page 319 –Example fig. 14-6, page 321

Stored procedures4 3 types of parameters, 314 Procedures can have 3 types of parameters –IN used for input –OUT used for output side effects  hard to read / debug the code –INOUT used for input + output –Examples scottTigerStoredProcedures.sql Functions –standard: only IN parameters –Oracle: all kinds of parameters Don’t use OUT and INOUT with functions!

Stored procedures5 Calling a stored procedure, 314 Syntax –procedureName(formalParameter1, formalParameter2, …) –Examples page ways to link formal and actual parameters –Position Like Java: 1 st parameter formal parameter linked to 1 st actual parameter, etc. Examples: –Figure 14-2, page 316 –calling insertDept in scottTigerStoredProcedures.sql –Named Syntax: formalParameterName => value Example: calling insertDept in scottTigerStoredProcedures.sql

Stored procedures6 Some PL/SQL to use in the body of stored procedures and functions call pName(parameters) –call another procedure return value –return from a function variable := value –assignment begin … end –statement group if condition then statements else statements end if –Example page 329 For loop While loop General loop –Inner exit statement

Stored procedures7 SQL statements Stored procedures / functions can contain SQL statements –select, insert, update, delete Select syntax [result: one value] –select attr into variable from … Example: searchDept, figure 14-4, page 318 Insert example –insertDept (my own example)

Stored procedures8 Cursors, 268 Cursor points to the current row. –Very much like JDBC Example. totalSalary, fig. 14-3, page 317 DECLARE cName CURSOR FOR select statement –declares the select statement –JDBC statement object OPEN cName –Executes the select statement –JDBC ResultSet rs = statement.executeQuery(…)

Stored procedures9 Exception handling Stored procedures can handles exception –Similar to Java try … catch … –Syntax page 314 –Example search_emp + searchDept, fig. 14-4, page 318 –Fig. 12-7, page 282 Predefined/named system exceptions –When others Catches exceptions not already caught –General strategy Don’t catch exceptions if you don’t know how to handle them properly Writing to the screen is usually not enough

Stored procedures10 Calling a function, 320 Functions can be called from –PL/SQL block (like the body of another procedure / function) Example fig. 14-7, page 321 –SQL statement Example page 323

Stored procedures11 Compiling and recompiling stored procedures, 317 Stored procedures / functions are automatically compiled when recreated. If one of the tables used in a procedures is altered the procedure / function must be recompiled –Alter procedure procedureName compile;

Stored procedures12 Packages, 323 A packages groups a set of logically connected stored procedures, functions, etc. –Kind of module Built-in packages in Oracle –STANDARD Many functions used in Oracle –DBMS_OUTPUT Put_line and other procedures Example fig. 14-7, page 321 You can create your own packages!

Stored procedures13 Package structure, 324 Package specification –Specification of procedures, functions, etc. Public part of the package Syntax page 324 Example fig , page 325 Package body –Implementation of procedures, functions, etc. Private part of the package Syntax page 325 Example fig , page 327

Stored procedures14 Calling a procedure / function in a package, 326 Name of procedure / function must be prefixed with the name of the package –PackageName.ProcedureName(…) –DBMS_OUTPUT.PUT_LINE(…) –myPackage.myProcedure(…) –Example fig , page 328

Stored procedures15 Java JDBC API Pakken java.sql –interface CallableStatement –"factoried" by a connection object CallableStatement prepareCall(String sql)CallableStatementString cst = prepareCall("{call insertDept(?, ?, ?)}"); –CallableStatement extends PreparedStatement PreparedStatement extends Statement

Stored procedures16 JDBC examples Stored procedure with IN parameters Stored procedure with IN and OUT parameters Stored function –CallableStatementExample.java

Stored procedures17 Handling parameters IN parameters –handled like parameters to prepared statements cstm.setString(1, 'Anders'); cstm.setXxx(position, value); OUT parameters + results from functions –register type before executing the call cstm.registerOutParameter(position, type) –results can be obtained after executing the call value = cstm.getXxx(position)