1. A Guide to SQL, Seventh Edition

2. Objectives Embed SQL commands in PL/SQL programs Retrieve single rows using embedded SQL Update a table using embedded INSERT, UPDATE, and DELETE commands Use cursors to retrieve multiple rows in embedded SQL A Guide to SQL, Seventh Edition

3. Objectives Update a database using cursors Manage errors in programs containing embedded SQL commands Use SQL in a language that does not support embedded SQL commands A Guide to SQL, Seventh Edition

4. Introduction A procedural language requires a step-by-step process to accomplish tasks You can embed, or include, SQL commands in the programs using procedural languages Useful when needed tasks are beyond the capabilities of SQL A Guide to SQL, Seventh Edition

5. Using Prompt Variables Sources of input for SQL commands  Onscreen form  Passed as arguments from procedure  Prompt variables Prompt variables are when user is prompted to enter a value when the program is run Precede the variable with an “&” A Guide to SQL, Seventh Edition

7. PL/SQL Programs Embed SQL commands in PL/SQL programs Create and save the programs as script files Run the script files to run the programs A Guide to SQL, Seventh Edition

8. Retrieving a Single Row and Column To place the results of a command in a variable, use the INTO clause  SELECT LAST_NAME INTO I_LAST_NAME FROM REP WHERE REP_NUM = ‘&I_REP_NUM;’ A Guide to SQL, Seventh Edition

9. Retrieving a Single Row and Column When executed, user will be prompted for a value for I_REP_NUM That value will be used to retrieve the last name of the sales rep whose number equals this value The results will be placed in the variable I_LAST_NAME This variable can be used in another program A Guide to SQL, Seventh Edition

10. Retrieving a Single Row and Column Procedure uses one argument and produces a single line of text containing this argument output To see the output, execute the command  SET SERVEROUTPUT ON Include this command in the PL/SQL program to ensure it will be executed A Guide to SQL, Seventh Edition

12. Retrieving a Single Row and Column Procedural code are commands that specify exactly what program is to do Procedural code located between BEGIN and END commands Each variable declaration and command as well as the word END are followed by semicolons A Guide to SQL, Seventh Edition

13. Retrieving a Single Row and Column The slash (/) at the end of the program appears on its own line When the script is run, the slash causes commands in the program to be executed immediately With the slash, commands are only loaded into memory Typing the slash runs the program A Guide to SQL, Seventh Edition

15. Using the %TYPE Attribute The %TYPE attribute ensures the variable has the same type as a particular column in a table Do not enter a data type  it is automatically assigned from the corresponding column  I_REP_NUM REP.REP_NUM%TYPE A Guide to SQL, Seventh Edition

16. Retrieving a Single Row from a Join Use embedded SQL commands to join tables A Guide to SQL, Seventh Edition

17. Inserting a Row into a Table When updating a database from the PL/SQL program, use appropriate SQL commands A Guide to SQL, Seventh Edition

19. Changing a Single Row in a Table Use the SQL command to insert rows in a database A Guide to SQL, Seventh Edition

20. Deleting Rows from a Table SQL commands are used to delete rows from a table A Guide to SQL, Seventh Edition

21. Multiple-Row Select PL/SQL can process only one record at a time A cursor is a pointer to a row in the collection of rows retrieved by a SQL command A cursor advances one row at a time to provide sequential one-record-at-a-time access to retrieved rows A Guide to SQL, Seventh Edition

22. Using Cursors The first step is to declare the cursor and describe the associated query in the declaration section  CURSOR CUSTGROUP IS SELECT CUSTOMER_NUM, CUSTOMER_NAME FROM CUSTOMER WHERE REP_NUM = ‘&I_REP_NUM’; Three commands are needed  OPEN, FETCH, CLOSE A Guide to SQL, Seventh Edition

23. Opening a Cursor OPEN command  Opens cursor  Causes query to be executed  Makes results available to the program Prior to opening, there are no rows available to be fetched OPEN CUSTGROUP A Guide to SQL, Seventh Edition

25. Fetching Rows from a Cursor FETCH command  Advances cursor to next row in set of retrieved rows  Places contents of row in indicated variables FETCH CUSTGROUP I_CUSTOMER_NUM, I_CUSTOMER_NAME; Execution of fetch command produces only a single row A Guide to SQL, Seventh Edition

28. Closing a Cursor CLOSE command  Closes a cursor  Deactivates it  Data retrieved by execution of the query is no longer available A Guide to SQL, Seventh Edition

31. More Complex Cursors Any SLQ query is legitimate in a cursor definition More complicated retrieval requirements result in greater benefits A Guide to SQL, Seventh Edition

34. Advantages of Cursors Simplified coding in the program Progams with embedded SQL utilizes the optimizer  Programmer doesn’t worry about the best way to retrieve data  Program doesn’t have to change even if the underlying structure does Cursor definition only changes; not procedural code A Guide to SQL, Seventh Edition

35. Updating Cursors Update the rows encountered in processing cursors with FOR UPDATE OF A Guide to SQL, Seventh Edition

37. Error Handling Handle errors with the EXCEPTION command A Guide to SQL, Seventh Edition

38. Using SQL in Microsoft Access Programs In Access, programs are written in Visual Basic Does not allow inclusion of SQL commands in the code If the SQL command is store in string variable, use the DoCmd.RunSQL command A Guide to SQL, Seventh Edition

39. Deleting Rows Place the SQL command in the procedure, including arguments Example  DELETE FROM REP WHERE REP_NUM = ’20’ A Guide to SQL, Seventh Edition

41. Running the Code Normally run by calling it from another procedure or by associating it with an event Can be run by using the Immediate window Normally for testing A Guide to SQL, Seventh Edition

43. Updating Rows Similar to the procedure to delete a sales rep, except  Need the UPDATE command  Two arguments rather than one Two portions of the construction of the SQL command that involve variables A Guide to SQL, Seventh Edition

45. Inserting Rows Process is similar Create the appropriate INSERT command in the strSQL variable Multiple arguments Once for each value inserted A Guide to SQL, Seventh Edition

46. Finding Rows SELECT commands handled differently than in PL/SQL No cursors Handle results of query just as you would use a loop to process through the records on the table A Guide to SQL, Seventh Edition

49. Summary How to embed SQL commands in PL Created programs  Retrieved single rows  Inserted new rows  Changed and deleted existing rows Cursors to update database Error Handling Using SQL command in Access A Guide to SQL, Seventh Edition