Creating Parameters for Report

IV Creating Parameters for Report

About parameters

A parameter is a variable whose value can be set at runtime (for example, from the Runtime Parameter Form or the command line). Parameters are especially useful for modifying SELECT statements and setting PL/SQL variables at runtime.

Reports Builder automatically creates a set of system parameters at runtime, but we can create our own as well. We can create parameters to replace either single literal values or entire expressions in any part of a query. We can reference parameters elsewhere in the report, such as in PL/SQL constructs providing conditional logic for the report.

Note: While you can delete or rename a user parameter, you cannot delete or rename a system parameter.

Parameter values can be specified in these ways:

·         Accepting the default parameter values (default values are set in the Parameter properties and you can control whether the values are displayed at runtime on the Runtime Parameter Form).

·         Typing the parameter value(s) as arguments on the command line (where applicable). Parameters specified on the command line override the equivalent system parameter values set in the report definition.

·         Choosing from a list or entering the parameter value(s) in the Runtime Parameter Form.

System parameters

Oracle Reports providing the following system parameters. We can change their default values.

System parameter descriptions

System Parameter	Description
COPIES	Is the number of report copies that should be made when the report is printed.
DESFORMAT	Is either: the output format for the report (for example, PDF, HTML, HTMLCSS, RTF, XML, SPREADSHEET, DELIMITED, or DELIMITEDDATA for bitmapped reports). the printer definition to use when formatting the report when DESTYPE=FILE and DESNAME=filename. If MODE=BITMAP, this is the name of the printer. If MODE=CHARACTER, this is the character mode printer definition file (.prt file).
DESNAME	Is the name of the output device (for example, the file name, printer's name, mail user ID).
DESTYPE	Is the type of device that will receive the report output (for example, SCREEN (to format the report using screen fonts), FILE, PRINTER, MAIL, SYSOUT, CACHE, or LOCALFILE.
MODE	Is whether the report should run in CHARACTER mode or BITMAP.
ORIENTATION	Is the print direction for the report (LANDSCAPE, PORTRAIT, DEFAULT).
PRINTJOB	Is whether the Print Job dialog box should appear before the report is run.

  

User Parameters 

We can create a user parameter in the following ways:

·         Create a parameter in the Object Navigator.

·         Use a bind parameter reference in a query, which causes Reports Builder to automatically create the parameter the first time it is referenced

Creating a user parameter

Note: Reports Builder automatically creates a user parameter when you use a bind parameter

Reference in a query

To create a user parameter:

1.      In the Object Navigator, expand the Data Model node, then click the User Parameters node.

2.      Click the Create button in the toolbar.

3.      Double-click the properties icon for the new parameter to display the Property Inspector.

4.      Under the General Information node, replace the Name property with the desired parameter name.

5.      Under the Parameter node, set the Initial Value and List of Values properties, if required.

6.      To validate the parameter's value at runtime, set the Validation Trigger property by clicking property field to display the PL/SQL Editor and define the PL/SQL to be triggered at runtime.

LOV for User Parameters

Creating a list of values (LOV) for a parameter

To create a LOV for a parameter:

1.      In the Object Navigator, expand the Data Model node, then the User Parameters node.

2.      Double-click the properties icon for the parameter for which you want to create a LOV to display the Property Inspector.

3.      Under the Parameter node, double-click the List of Values property field to display the Parameter List of Values dialog box.

4.      Select the type of list that you want to create:

·         For Static Values, type a value in the Value text box and click Add. Repeat for each value you want to add. (Click Remove to delete items from the list)

·         For SELECT Statement, type a query to populate the list of values. You can select more than one column to display in the LOV, where the first column contains the value to be assigned to the parameter. The LOV displays columns in the order specified in the query.

5.      If you want the parameter value to be restricted to only those in the LOV, select the Restrict List to Predetermined Values check box. To display a combo box that allows users to edit values or type a different value in the Runtime Parameter Form, clear the check box.

6.      If you do not want the first column (which contains the parameter value) of your query displayed in the LOV, select the Hide First Column check box. If there is no need to preserve the confidentiality of the first column, clear the check box.

Caution: If you send the report output to an HTML file, either from Reports Builder or running it in your Web browser, the value of the first column will be visible in the HTML source, even if Hide First Column is selected. If you run the report from a Web browser and the list of values is unrestricted, the HTML Parameter Form will display a text field instead of a combo box, and a list of static values that you can copy and paste into the text field. In this case, the first column will always be shown in the Parameter Form, even if Hide First Column is selected.

7.      Click OK.

Bind Variables

Bind references (or bind variables) are used to replace a single value in SQL or PL/SQL, such as a character string, number, or date. Specifically, bind references may be used to replace expressions in SELECT, WHERE, GROUP BY, ORDER BY, HAVING, CONNECT BY, and START WITH clauses of queries. Bind references may not be referenced in FROM clauses or in place of reserved words or clauses.


We can create a bind reference by typing a colon (:) followed immediately by the column or parameter name. If you do not create a column or parameter before making a bind reference to it in a SELECT statement, Reports Builder will create a parameter for you by default.

Restrictions: Bind references must not be the same name as any reserved SQL keywords.

Example 1: SELECT clause

In the following example, the value of DFLTCOMM replaces null values of COMMPLAN in the rows selected.

SELECT CUSTID, NVL(COMMPLAN, :DFLTCOMM) COMMPLAN

  FROM ORD;

Example 2: WHERE clause

The value of CUST is used to select a single customer.

SELECT ORDID, TOTAL

  FROM ORD

  WHERE CUSTID = :CUST;

Example 3: GROUP BY clause

All non-aggregate expressions such as NVL(COMMPLAN, :DFLTCOMM) in the SELECT clause must be replicated in the GROUP BY clause.

SELECT NVL(COMMPLAN, :DFLTCOMM) COMMPLAN, SUM(TOTAL) TOTAL

  FROM ORD

GROUP BY NVL(COMMPLAN, :DFLTCOMM);

Example 4: HAVING clause 

The value of MINTOTAL is used to select customers with a minimum total of orders.

SELECT CUSTID, SUM(TOTAL) TOTAL

  FROM ORD

  GROUP BY CUSTID HAVING SUM(TOTAL) > :MINTOTAL;

Example 5:  ORDER BY clause

The value of SORT is used to select either SHIPDATE or ORDERDATE as the sort criterion. Note that this is not the same as ORDER BY 1 because :SORT is used as a value rather than to identify the position of an expression in the SELECT list.


Note that DECODE is required in this example. You cannot use a bind variable in an ORDER BY clause unless it is with DECODE.

SELECT ORDID, SHIPDATE, ORDERDATE, TOTAL

  FROM ORD

  ORDER BY DECODE(:SORT, 1, SHIPDATE, 2, ORDERDATE);

Example 6:   CONNECT BY and START WITH clauses

References in CONNECT BY and START WITH clauses are used in the same way as they are in the WHERE and HAVING clauses.

Example 7:   PL/SQL

Procedure double is 

Begin; 

   :my_param := :my_param*2; 

End;

The value of myparam is multiplied by two and assigned to myparam.

About lexical references

Lexical references are placeholders for columns or parameters that you embed in a SELECT statement. You can use lexical references to replace the clauses appearing after SELECT, FROM, WHERE, GROUP BY, ORDER BY, HAVING, CONNECT BY, and START WITH. Use a lexical reference when you want the parameter to substitute multiple values at runtime.


We cannot make lexical references in a PL/SQL statement. You can, however, use a bind reference in PL/SQL to set the value of a parameter that is then referenced lexically in SQL, as shown in the example below.


We can create a lexical reference by typing an ampersand (&) followed immediately by the column or parameter name. A default definition is not provided for lexical references. Therefore, you must do the following:

·         Before you create your query, define a column or parameter in the data model for each lexical reference in the query. For columns, you must set the Value if Null property, and, for parameters, you must set the Initial Value property. Reports Builder uses these values to validate a query with a lexical reference.

·         Create your query containing lexical references.

Restrictions

·         You cannot make lexical references in a PL/SQL statement.

·         If a column or parameter is used as a lexical reference in a query, its Datatype must be Character.

·         If you want to use lexical references in your SELECT clause, you should create a separate lexical reference for each column you will substitute. In addition, you should assign an alias to each lexical reference. This enables you to use the same layout field and boilerplate label for whatever value you enter for the lexical reference on the Runtime Parameter Form.

·         If you use lexical references in your SELECT clause, you must specify the same number of items at runtime as were specified in the report's data model. Each value you specify for your lexical references at runtime must have the same datatype as its Initial Value.

·         If you use lexical references in your SELECT clause, the width of the column is derived from the Initial Value property of the parameter. Consequently, you should ensure that the Initial Value of the parameter corresponds to the widest column that you intend to use.

·         A Reports Builder link should not depend upon a lexical reference. That is, neither the child column of a link or its table name should be determined by a lexical reference. To achieve this functionality, you need to create a link with no columns specified and then enter the SQL clause (for example, WHERE) for the link directly in the query. For example, your parent and child queries might be written as follows:

Parent Query:

SELECT DEPTNO FROM EMP

Child Query:

SELECT &PARM_1 COL_1, &PARM2 COL_2

  FROM EMP

  WHERE &PARM_1 = :DEPTNO

Note how the WHERE clause makes a bind reference to DEPTNO, which was selected in the parent query. Also, this example assumes that you have created a link between the queries in the Data Model view with no columns specified.

·         A lexical reference cannot be used to create additional bind variables after the After Form trigger fires. For example, suppose you have a query like the following (note that the WHERE clause is replaced by a lexical reference):

·                SELECT ENAME, SAL FROM EMP  &where_clause

·          If the value of the where_clause parameter contains a reference to a
bind variable, you must specify the value in the After Form trigger or earlier.
You would get an error if you supplied the following value for the parameter in
the Before Report trigger:

WHERE SAL = :new_bind

If you supplied this same value in the After Form trigger, the report would run.

Example 1: SELECT clause

SELECT &P_ENAME NAME, &P_EMPNO ENO, &P_JOB ROLE

  FROM EMP;

P_ENAME, P_EMPNO, and P_JOB can be used to change the columns selected at runtime. For example, you could enter DEPTNO as the value for P_EMPNO on the Runtime Parameter Form. Note that in this case, you should use aliases for your columns. Otherwise, if you change the columns selected at runtime, the column names in the SELECT list will not match the Reports Builder columns and the report will not run.

Example 2: FROM clause

SELECT ORDID, TOTAL

  FROM &ATABLE;

A TABLE can be used to change the table from which columns are selected at runtime. For example, you could enter ORD for ATABLE at runtime. If you dynamically change the table name in this way, you may also want to use lexical references for the SELECT clause (look at the previous example) in case the column names differ between tables.

Example 3: WHERE clause

SELECT ORDID, TOTAL

  FROM ORD

  WHERE &CUST;

CUST can be used to restrict records retrieved from ORD. Any form of the WHERE clause can be specified at runtime.

Example 4: GROUP BY clause

SELECT NVL(COMMPLAN, DFLTCOMM) CPLAN, SUM(TOTAL) TOTAL

  FROM ORD

  GROUP BY &NEWCOMM;

The value of NEWCOMM can be used to define the GROUP BY clause.

Example 5: HAVING clause

SELECT CUSTID, SUM(TOTAL) TOTAL

  FROM ORD

  GROUP BY CUSTID HAVING &MINTOTAL;

The value of MINTOTAL could, for example, be used to select customers with a minimum total of orders.

Example 6: ORDER BY clause

SELECT ORDID, SHIPDATE, ORDERDATE, TOTAL

  FROM ORD

  ORDER BY &SORT;

The value of SORT can be used to select SHIPDATE, ORDERDATE, ORDID, or any combination as the sort criterion. It could also be used to add on to the query, for example to add a CONNECT BY and START WITH clause.

Example 7: CONNECT BY and START WITH clauses

Parameters in CONNECT BY and START WITH clauses are used in the same way as they are in the WHERE and HAVING clauses.

Example 8: Multiple clauses

               SELECT &COLSTABLE;

COLSTABLE could be used to change both the SELECT and FROM clauses at runtime. For example, you could enter DNAME ENAME, LOC SAL FROM DEPT for COLSTABLE at runtime.

               SELECT * FROM EMP &WHEREORD;

WHEREORD could be used to change both the WHERE and ORDER BY clauses at runtime. For example, you could enter WHERE SAL > 1000 ORDER BY DEPTNO for &WHEREORD at runtime.

Example 9: PL/SQL and SQL 

SELECT &BREAK_COL C1, MAX(SAL)

  FROM EMP

  GROUP BY &BREAK_COL;

BREAK_COL is used to change both the SELECT list and the GROUP BY clause at runtime. The Initial Value of the parameter &BREAK_COL is JOB. At runtime, the user of the report can provide a value for a parameter called GROUP_BY_COLUMN (of data type Character).
In the Validation Trigger for GROUP_BY_COLUMN, you call the following PL/SQL procedure and pass it the value of GROUP_BY_COLUMN:

procedure conv_param (in_var IN char) is

begin

  if upper(in_var) in ('DEPTNO','EMPNO','HIREDATE') then

    :break_col := 'to_char('||in_var||')' ;

  else

    :break_col := in_var;

  end if;

end;

This PL/SQL ensures that, if necessary, a TO_CHAR is placed around the break column the user chooses. Notice how in SQL, you make a lexical reference to BREAK_COL. In PL/SQL, you must make a bind reference to BREAK_COL because lexical references are not allowed in PL/SQL.

Differences between bind and lexical references

Bind references are used to replace a single value in SQL or PL/SQL. Specifically, bind references may be used to replace expressions in SELECT, WHERE, GROUP BY, ORDER BY, HAVING, CONNECT BY, and START WITH clauses of queries. Bind references may not be referenced in the FROM clause.


An example is:

SELECT ORDID,TOTAL 

  FROM ORD

  WHERE CUSTID = :CUST

Lexical references are placeholders for text that you embed in a SELECT statement, when you want the parameter to substitute multiple values at runtime. You can use lexical references to replace the clauses appearing after SELECT, FROM, WHERE, GROUP BY, ORDER BY, HAVING, CONNECT BY, and START WITH. You cannot make lexical references in PL/SQL. Before you reference a lexical parameter for a column or table, you must have predefined the parameter and given it an initial value. 


An example is:

SELECT ORDID, TOTAL

  FROM &ATABLE