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Producing Readable Output With SQL * Plus (Continued)

Producing Readable Output With SQL * Plus (Continued). Using the && Substitution Variable. Use the double ampersand (&&) if you want to reuse the variable value without prompting the user each time. The user will see the prompt for the value only once. Using the && Substitution Variable.

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Producing Readable Output With SQL * Plus (Continued)

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  1. Producing Readable Output With SQL * Plus (Continued)

  2. Using the && Substitution Variable • Use the double ampersand (&&) if you want to reuse the variable value without prompting the user each time. • The user will see the prompt for the value only once.

  3. Using the && Substitution Variable SELECT employee_id, first_name, job_id, &&column_name FROM employees ORDER BY &column_name

  4. Defining User Variable • You can predefine variables using one of two SQL *Plus commands: • DEFINE: Creates a CHAR datatype user variable • ACCEPT: Read user input and store it in a variable. • If you need to predefine a variable that includes spaces, you must enclose the value within single quotation marks when using the DEFINE commands.

  5. The ACCEPT Command • Creates a customized prompt when accepting user input. • Explicitly defines a NUMBER or DATE datatype variable. • Hides user input for security reason. ACCEPT variable [datatype] [FORMAT format] [PROMPT text] [HIDE]

  6. The ACCEPT Command In the syntax: • variable is the name of the variable that stores the value (If it does not exist, SQL*Plus creates it.) • datatype is NUMBER, CHAR, or DATE (CHAR has a maximum length limit of 240 bytes. DATE checks against a formal model, and the datatype is CHAR.) • FORMAT specifies the format model-for example, A10 or 9.999 • PROMPT displays the text before the user can enter the value. • HIDE suppresses what the user enters-for example, a password.

  7. Using the ACCEPT Command SQL> ACCEPT p_dept_name PROMPT 'Provide the department name:‘ SQL> SELECT * 2 FROM departments 3 where department_name = UPPER ('&p_dept_name');

  8. DEFINE and UNDEFINE commands • A variable remains defined until you either : • Use the UNDEFINE command to clear it • Exit SQL*Plus • You can verify your changes with the DEFINE command. • To define variable for every session, modify your login.sql file so that the variable are created at startup.

  9. Using the DEFINE Command • Create a variable to hold the department name • Use the variable as you would with any other variable SQL> DEFINE p_dept_name = IT SQL> DEFINE p_dept_name DEFINE P_DEPT_NAME = "IT" (CHAR) SQL> SELECT * 2 FROM departments 3 WHERE department_name = UPPER ('&p_dept_name');

  10. Customizing the SQL* Plus Environment • Use SET commands to control current session • Verify what you have set by using the SHOW command SET system_variable value SQL> SET ECHO ON SQL> SHOW ECHO echo ON

  11. Continued…. • You can control the environment in which SQL*Plus is currently operating by using the SET commandes. • In this syntax: • system_variable : is a variable that controls one aspect of the session environment • value : is a value for the system variable. • You can verify what you have set by using the SHOW command. The SHOW command on the side checks whether ECHO had been set on or off. • To see all SET variable values, use the SHOW ALL command.

  12. SET command variables The value n represents a numeric value.

  13. Saving Customization in the login.sql File. • The login.sql file contains standard SET and other SQL*Plus commands that are implemented at login. The file is read and commands are implemented at login. • When you log out of your session, all customized settings are lost. • You can modify login.sql to contain additional SET commands. • All permanent settings to the login.sql file.

  14. SQL*Plus Format Commands

  15. The COLUMN Command

  16. Using the COLUMN command • Create column headings • Display the current setting for the first_name column • Clear setting for the first_name column COLUMN first_name HEADING ‘Employee|Name’ FORMAT A15 COLUMN salary JUSTIFY LEFT FORMAT $99,990.00 COLUMN manager_id FORMAT 999999999 NULL ‘No Manager’ COLUMN first_name COLUMN first_name CLEAR

  17. Displaying or Clearing Settings If you have a lengthy command, you can continue it on the next line by ending the current line with a hyphen (-)

  18. Using the BREAK command • Suppresses duplicates and section rows • To suppress duplicates • To section out rows at break values • To ensure that the BREAK command works effectively, use the ORDER BY clause to order the columns that you are breaking on. SQL> BREAK ON first_name ON job SQL> BREAK ON first_name SKIP 4 ON job SKIP 2

  19. Summary • Use SQL*Plus substitution variables to temporarily store values • Use SET commands to control current SQL*Plus environment • Use the ACCEPT and DEFINE commands to predefine variables in SQL*Plus • Use the COLUMN command to control the display of a column. • Use the BREAK command to suppress duplicates and section rows.

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