Informix
SELECT
The SELECT statement contains input variables and output variables.
Input variables are passed to the database as part of the execution and
the substitution as described above for DELETE, INSERT, and UPDATE. Output
variables are used to return values based on the result of the SELECT
statement.
Example 1
Assume you enter the following statement:
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SELECT emp_name, emp_salary INTO :emp_name_var, :emp_salary_var FROM employee WHERE emp_id = :emp_id_var; |
Here emp_id_var, emp_salary_var, and emp_name_var are PowerScript
variables defined within the scope of the script that contains the SELECT
statement, emp_id_var is processed as described in the DELETE example
above.
Both emp_name_var and emp_salary_var are output variables that will
be used to return values from the database. The data types of emp_name_var
and emp_salary_var should be the PowerScript data types that best match
the Informix data type. When the data types do not match perfectly,
PowerBuilder converts them.
How big should numeric output variables be?
For numeric data, the output variable must be large enough to hold
any value that may come from the database.
Assume the value for emp_id_var is 691 as in the previous example.
When the SELECT statement executes, the database receives the following
statement:
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SELECT emp_name, emp_salary FROM employee WHERE emp_id = 691; |
If no errors are returned on the execution, data locations are
internally bound for the result fields. The data returned into these
locations is converted if necessary and the appropriate PowerScript
variables are set to those values.
Example 2
This example assumes the default transaction object (SQLCA) has been
assigned valid values and a successful CONNECT has executed. It also
assumes the data type of the emp_id column in the employee table is
CHARACTER[10].
The user enters an employee ID into the line edit sle_Emp and clicks
the button Cb_Delete to delete the employee.
The script for the Clicked event in the CommandButton Cb_Delete
is:
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// Make sure we have a value. if sle_Emp.text <> "" then // Since we have a value, let's try to delete it. DELETE FROM employee WHERE emp_id = :sle_Emp.text; // Test to see if the DELETE worked. if SQLCA.sqlcode = 0 then // It seems to have worked, let user know. MessageBox( "Delete",& "The delete has been successfully processed!") else // It didn't work. MessageBox( "Error", & "The delete failed. Employee ID is not valid.") end if else // No input value. Prompt user. MessageBox( "Error", & "An employee ID is required for "+"delete!" ) end if |
Error checking
Although you should test the SQLCode after every SQL statement,
these examples show statements to test the SQLCode only to illustrate a
specific point.
Example 3
This example assumes the default transaction object (SQLCA) has been
assigned valid values and a successful CONNECT has executed. The user
wants to extract rows from the employee table and insert them into the
table named extract_employees.
The extraction occurs when the user clicks the button Cb_Extract.
The boolean variable YoungWorkers is set to TRUE or FALSE elsewhere in the
application.
The script for the Clicked event for the CommandButton Cb_Extract
is:
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integer EmployeeAgeLowerLimit integer EmployeeAgeUpperLimit // Do they have young workers? if ( YoungWorkers = TRUE ) then // Yes - set the age limit in the YOUNG range. // Assume no employee is under legal working age. EmployeeAgeLowerLimit = 16 // Pick an upper limit. EmployeeAgeUpperLimit = 42 else // No - set the age limit in the OLDER range. EmployeeAgeLowerLimit = 43 // Pick an upper limit that includes all // employees. EmployeeAgeUpperLimit = 200 end if INSERT INTO extract_employees(emp_id,emp_name) SELECT emp_id, emp_name FROM employee WHERE emp_age >= :EmployeeAgeLowerLimit AND emp_age <= :EmployeeAgeUpperLimit; |