Tài liệu Summary of PL / SQL pdf

Summary of PL/SQL 26 Introduction to Oracle: SQL and PL/SQL Using Procedure Builder26Ć2 Summary of PL/SQL 26Ć3 Summary PL/SQL (Procedural Language/SQL) is an extension to SQL. It is a language that allows you to combine multiple SQL statements with procedural controls such as identifiers, conditional, and iterative constructs in a PL/SQL block. Benefits from PL/SQL D Modularize program development by grouping similar concepts together and nesting blocks D Declare identifiers, for example, variables, constants, and cursors D Program with procedural language structures, for example, IF statements and loops D Exception handling for Oracle7 Server errors and user-defined exceptions D Port code between applications and the Oracle7 Server D Integrate Oracle7 stored subprograms and application subprograms D Improve performance by sending a block of code to the server PL/SQL Block A PL/SQL block contains code in up to four sections. The header section is where you set the name and parameters for named blocks. The declarative section is optional and contains all variables, constants, cursors, and user-defined exceptions that will be referenced within the executable section. The executable section is required and contains SQL statements to manipulate data in the database and PL/SQL statements to manipulate data in the block. The exception-handling section is optional and specifies the actions to perform when errors and abnormal conditions arise within the executable section. Anonymous Blocks Anonymous blocks are unnamed blocks. They are declared at the point in an application where they are to be executed and are passed to the PL/SQL engine for execution at runtime. You can embed an anonymous block within a precompiler program and within SQL*Plus or Server Manager. Triggers in Developer/2000 components consist of such blocks. Introduction to Oracle: SQL and PL/SQL Using Procedure Builder26Ć4 Summary of PL/SQL 26Ć5 Summary continued Procedures Procedures are named PL/SQL blocks that store a series of actions for later execution. The procedure can contain zero or more parameters, which are arguments that you list when calling the procedure. Procedures can either be application specific or stored in the Oracle7 Server. Functions A function returns a value to the calling environment. You must declare the RETURN datatype in the header section of the function definition, and define the value to be returned in the PL/SQL block. You can also declare a list of parameters to be passed into the function. Functions are called as part of an expression. DML in PL/SQL You can use DML statements in your PL/SQL blocks. Use the SELECT statement to retrieve data from the database. D The SELECT statement contains an additional mandatory clause: the INTO clause. In the INTO clause, list the output variables for receiving the data. The SELECT statement must return exactly one row or an error will occur. D The INSERT statement adds new rows of data to the table. D The UPDATE statement modifies existing rows in the table. D The DELETE statement removes unwanted rows from the table. D COMMIT ends the current transaction by making all pending changes to the database permanent. D ROLLBACK ends the current transaction by discarding all pending changes. Introduction to Oracle: SQL and PL/SQL Using Procedure Builder26Ć6 Summary of PL/SQL 26Ć7 Summary continued IF Conditional Statements The PL/SQL IF statement is similar to the structure of IF statements in other procedural languages. It allows PL/SQL to perform actions selectively based upon conditions. If the controlling Boolean condition is TRUE, the associated sequence of statements is executed; if the controlling Boolean condition is FALSE or NULL, the associated sequence of statements is passed over. Iterative Loop Statements You can use one of three loop structures to repeat a sequence of statements. D The basic loop consists of the body of statements to be repeated enclosed between the delimiters LOOP and END LOOP. This uncontrolled loop is an infinite loop that is to be avoided. To avoid an infinite loop, add an EXIT statement. D FOR loops have a control statement at the front of the LOOP keyword to determine the number of iterations PL/SQL performs. D The WHILE loop repeats a sequence of statements until the controlling condition is no longer TRUE. The condition is evaluated at the start of each iteration. Cursors PL/SQL cursors let you name a private SQL area and access its stored information. The cursor directs all phases of processing. Explicit cursors are declared and named by the programmer and manipulated through specific statements within the block’s executable actions. Control explicit cursors in a loop with four steps: declare, open, fetch, and close. Cursor FOR loops are a shortcut to open the cursor, fetch rows once for each loop iteration, and automatically close the cursor after all rows are processed. Exception Handling An exception is an identifier in PL/SQL, raised during the execution of a block that terminates its main body of actions. A block will always terminate when PL/SQL raises an exception, but you specify an exception handler to perform final actions. Exceptions can be raised either by the Oracle7 Server or by the user. You can either trap an exception in the exception-handling section of the block, or allow it to propagate to the calling environment. Procedure Builder Oracle Procedure Builder is a tool you can use to create, execute, and debug PL/SQL programs used in your application tools, such as a form or report, or on the Oracle7 Server through its graphical interface. Introduction to Oracle: SQL and PL/SQL Using Procedure Builder26Ć8 Summary of PL/SQL 26Ć9 Practice Overview This practice has you build a PL/SQL-based application to insert, update, and delete records in a video store database and generate a report. The database contains only the essential tables. Practice Contents D Creating procedures and functions D Inserting, updating, and deleting data D Incorporating IF statements and loops D Handling exceptions Note: If you are new to the class, you can execute the buildvid.sql script in SQL*Plus to create and populate the tables. If you want to drop the work you did in the course summary from the SQL section, you can execute the dropvid.sql script in SQL*Plus to drop their tables. Then, you can execute the buildvid.sql script in SQL*Plus to create and populate the tables. Introduction to Oracle: SQL and PL/SQL Using Procedure Builder26Ć10 [...]... procedure DAMAGED_COPY g Create a procedure named TOP_RENTAL to determine the top rental Allow for more than one top rental Store the names and a message of the top rentals in the RESULTS table Summary of PL/ SQL 26Ć11 26Ć12 Introduction to Oracle: SQL and PL/ SQL Using Procedure Builder ...Practice 26 Entity Relationship Diagram The facing page contains an entity relationship diagram depicting the tables and columns for a small movie rental application 1 Complete the database design by writing subprograms to perform the following actions a Create a function named NEW_MEMBER to return the membership number for that new member Be sure to use a sequence... Check the data dictionary for the sequence name b Create a function named NEW_RENTAL to record a new rental based on a member’s last name Return a message with the expected due date If two or more people have the same last name, store the first name, last name, phone, and membership number for all matching last names in the RESULTS table c Create a procedure named MEM_TITLES to retrieve all the titles . Summary of PL/ SQL 26 Introduction to Oracle: SQL and PL/ SQL Using Procedure Builder26Ć2 Summary of PL/ SQL 26Ć3 Summary PL/ SQL (Procedural Language /SQL) . changes. Introduction to Oracle: SQL and PL/ SQL Using Procedure Builder26Ć6 Summary of PL/ SQL 26Ć7 Summary continued IF Conditional Statements The PL/ SQL IF statement