Lab 1 Writing Interactive Queries CISB514 Advanced Database Systems

Objectives After completing this lesson, you should be able to:  Write ACCEPT commands to get numeric, character, or date input values from the user  Compose queries with substitution variables to utilize input values from the user

Using the ACCEPT Command The basic syntax: ACCEPT p_variable_name DATATYPE FORMAT ‘format_model’ PROMPT ‘message’ Use the p_ prefix to identify a substitution variable. By default, CHAR is assumed if no datatype is specified. Clearly indicate the expected value / format. Specify a format model as a form of data validation.

Using Substitution Variables Use it in any part of a SELECT statement to specify: What columns to display What tables to use What conditions to be met Etc Precede the variable name with a single ampersand character (&) when being used in a query

Example: Accepting a NUMBER Value for the Search Condition ACCEPT p_location_id NUMBER PROMPT ‘Enter a location ID: ’ SELECT * FROM departments WHERE location_id = &p_location_id Key in 1400, 1500, 1700, 1800, 2400, 2500, or 2700 for results.

Example: Accepting a CHAR Value for the Search Condition ACCEPT p_department_name PROMPT ‘Enter a department name (wildcard characters allowed): ’ SELECT * FROM departments WHERE UPPER(department_name) LIKE UPPER(‘&p_department_name’) Key in it, it%, or %it% and see the difference.

Example: Accepting a DATE Value for the Search Condition ACCEPT p_hire_date DATE FORMAT 'DD/MM/YYYY' PROMPT 'Enter a date (in DD/MM/YYYY format) : ' SELECT * FROM employees WHERE hire_date = TO_DATE('&p_hire_date’, 'DD/MM/YYYY') Key in 07/06/1994 for results. Specify the date format if other than the DD- MON-YYYY format.

Extras It is not mandatory to use the ACCEPT command and substitution variables together Substitution variables can replace any lexical unit (or combination of) in a query except for SELECT

Exercises 1. Write a script that:  Accepts two input values from the user:  minimum salary  maximum salary  Outputs job titles where minimum and maximum salaries fall between the two input values For results, enter 4000 and

Exercises 2. Write a script that:  Displays the names of departments and the their respective managers  Gets the user to specify whether to sort the results by department names or manager names. The user may specify actual column names (department_name or last_name) or use positional notation (1 or 2).

Exercises 3. Write a script that:  Outputs the number of people hired in each department  On a date specified by the user For results, enter 07-JUN-1994.

References For how to specify date format models, see 102/b14200/sql_elements004.htm#i /b14200/sql_elements004.htm#i34924