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 modifyingSELECT
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:
|
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 Parametersnode.
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 inSELECT
, WHERE
, GROUP BY
, ORDER BY
, HAVING
, CONNECT BY
, andSTART 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, FLTCOMM) 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, FLTCOMM)
in the SELECT
clause must be replicated in the GROUP BY
clause.SELECT NVL(COMMPLAN, FLTCOMM) COMMPLAN, SUM(TOTAL) TOTAL
FROM ORD
GROUP BY NVL(COMMPLAN, FLTCOMM);
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 anORDER 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 aSELECT
statement. You can use lexical references to replace the clauses appearing afterSELECT
, 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 = EPTNO
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 theSELECT
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 inSELECT
, 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 = :CUSTLexical 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
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