As discussed in Section 13.2.1 EDB-SPL is a block-structured language. The first section that can appear in a block is the declaration section. The declaration section contains the definition of variables, cursors, and other types that can be used in EDB-SPL statements contained in the block. In this section, variable declarations are examined in more detail.
Generally, all variables used in a block must be declared in the declaration section of the block. A variable declaration consists of a name that is assigned to the variable and its data type. (See Chapter 7 for a discussion of data types.) Optionally, the variable can be initialized to a default value in the variable declaration.
The general syntax of a variable declaration is:
name type [ := expression ];name is an identifier assigned to the variable. type is the data type assigned to the variable. [ := expression ], if given, specifies the initial value assigned to the variable when the block is entered. If the clause is not given then the variable is initialized to the SQL null value.
The default value is evaluated every time the block is entered. So, for example, assigning SYSDATE to a variable of type DATE causes the variable to have the time of the current invocation, not the time when the procedure or function was precompiled.
The following procedure illustrates some variable declarations that utilize defaults consisting of string and numeric expressions.
CREATE OR REPLACE PROCEDURE dept_salary_rpt (
p_deptno NUMBER
)
IS
todays_date DATE := SYSDATE;
rpt_title VARCHAR2(40) := 'Report For Department # ' || p_deptno || ' on ' || todays_date;
base_sal INTEGER := 35525;
base_comm_rate NUMBER := 1.33333;
base_annual NUMBER := ROUND(base_sal * base_comm_rate, 2);
BEGIN
DBMS_OUTPUT.PUT_LINE(rpt_title);
DBMS_OUTPUT.PUT_LINE('Base Annual Salary: ' || base_annual);
END;
The following output of the above procedure shows that default values in the variable declarations are indeed assigned to the variables.
EXEC dept_salary_rpt(10); Report For Department # 10 on 05-APR-05 Base Annual Salary: 47366.55
Often times variables will be declared in EDB-SPL programs that will be used to hold values from tables in the database. In order to ensure compatibility between the table columns and the EDB-SPL variables, the data types of the two should be the same.
However, as quite often happens, a change might be made to the table definition. If the data type of the column is changed, the corresponding change may be required to the variable in the EDB-SPL program.
Instead of coding the specific column data type into the variable declaration the column attribute, %TYPE, can be used instead. A qualified column name in dot notation or the name of a previously declared variable must be specified as a prefix to %TYPE. The data type of the column or variable prefixed to %TYPE is assigned to the variable being declared. If the data type of the given column or variable changes, the new data type will be associated with the variable without the need to modify the declaration code.
Note: The %TYPE attribute can be used with formal parameter declarations as well.
name { table.column | variable }%TYPE;name is the identifier assigned to the variable or formal parameter that is being declared. column is the name of a column in table. variable is the name of a variable that was declared prior to the variable identified by name.
In the following example a procedure queries the emp table using an employee number, displays the employee's data, finds the average salary of all employees in the department to which the employee belongs, and then compares the chosen employee's salary with the department average.
CREATE OR REPLACE PROCEDURE emp_sal_query (
p_empno IN NUMBER
)
IS
v_ename VARCHAR2(10);
v_job VARCHAR2(9);
v_hiredate DATE;
v_sal NUMBER(7,2);
v_deptno NUMBER(2);
v_avgsal NUMBER(7,2);
BEGIN
SELECT ename, job, hiredate, sal, deptno
INTO v_ename, v_job, v_hiredate, v_sal, v_deptno
FROM emp WHERE empno = p_empno;
DBMS_OUTPUT.PUT_LINE('Employee # : ' || p_empno);
DBMS_OUTPUT.PUT_LINE('Name : ' || v_ename);
DBMS_OUTPUT.PUT_LINE('Job : ' || v_job);
DBMS_OUTPUT.PUT_LINE('Hire Date : ' || v_hiredate);
DBMS_OUTPUT.PUT_LINE('Salary : ' || v_sal);
DBMS_OUTPUT.PUT_LINE('Dept # : ' || v_deptno);
SELECT AVG(sal) INTO v_avgsal
FROM emp WHERE deptno = v_deptno;
IF v_sal > v_avgsal THEN
DBMS_OUTPUT.PUT_LINE('Employee''s salary is more than the department average of '
|| v_avgsal);
ELSE
DBMS_OUTPUT.PUT_LINE('Employee''s salary does not exceed the department average of '
|| v_avgsal);
END IF;
END;
Instead of the above, the procedure could be written as follows without explicitly coding the emp table data types into the declaration section of the procedure.
CREATE OR REPLACE PROCEDURE emp_sal_query (
p_empno IN emp.empno%TYPE
)
IS
v_ename emp.ename%TYPE;
v_job emp.job%TYPE;
v_hiredate emp.hiredate%TYPE;
v_sal emp.sal%TYPE;
v_deptno emp.deptno%TYPE;
v_avgsal v_sal%TYPE;
BEGIN
SELECT ename, job, hiredate, sal, deptno
INTO v_ename, v_job, v_hiredate, v_sal, v_deptno
FROM emp WHERE empno = p_empno;
DBMS_OUTPUT.PUT_LINE('Employee # : ' || p_empno);
DBMS_OUTPUT.PUT_LINE('Name : ' || v_ename);
DBMS_OUTPUT.PUT_LINE('Job : ' || v_job);
DBMS_OUTPUT.PUT_LINE('Hire Date : ' || v_hiredate);
DBMS_OUTPUT.PUT_LINE('Salary : ' || v_sal);
DBMS_OUTPUT.PUT_LINE('Dept # : ' || v_deptno);
SELECT AVG(sal) INTO v_avgsal
FROM emp WHERE deptno = v_deptno;
IF v_sal > v_avgsal THEN
DBMS_OUTPUT.PUT_LINE('Employee''s salary is more than the department average of '
|| v_avgsal);
ELSE
DBMS_OUTPUT.PUT_LINE('Employee''s salary does not exceed the department average of '
|| v_avgsal);
END IF;
END;
Note: p_empno shows an example of a formal parameter defined using %TYPE.
v_avgsal illustrates the usage of %TYPE referring to another variable instead of a table column.
The following is sample output from executing this procedure.
EXEC emp_sal_query(7698); Employee # : 7698 Name : BLAKE Job : MANAGER Hire Date : 01-MAY-81 Salary : 2850 Dept # : 30 Employee's salary is more than the department average of 1566.67
Using the %TYPE attribute provides an easy way to create a variable dependent upon a column's data type. Using the %ROWTYPE attribute, a record can be defined that contains fields corresponding to all columns of a given table. Each field takes on the data type of its corresponding column.
A record is a named, ordered collection of fields. A field is similar to a variable - it has an identifier and data type, but also has the property that it belongs to a record and must be referenced using dot notation with the record name as its qualifier.
A record can be declared using the %ROWTYPE attribute. The %ROWTYPE attribute is prefixed by a table name. Each column in the named table defines an identically named field in the record with the same data type as the column.
record table%ROWTYPE;
record is an identifier assigned to the record. table is the name of a table whose columns are to define the fields in the record.
The following example shows how the emp_sal_query procedure from the prior section can be modified to use emp%ROWTYPE to create a record named r_emp instead of declaring individual variables for the columns in emp.
CREATE OR REPLACE PROCEDURE emp_sal_query (
p_empno IN emp.empno%TYPE
)
IS
r_emp emp%ROWTYPE;
v_avgsal emp.sal%TYPE;
BEGIN
SELECT ename, job, hiredate, sal, deptno
INTO r_emp.ename, r_emp.job, r_emp.hiredate, r_emp.sal, r_emp.deptno
FROM emp WHERE empno = p_empno;
DBMS_OUTPUT.PUT_LINE('Employee # : ' || p_empno);
DBMS_OUTPUT.PUT_LINE('Name : ' || r_emp.ename);
DBMS_OUTPUT.PUT_LINE('Job : ' || r_emp.job);
DBMS_OUTPUT.PUT_LINE('Hire Date : ' || r_emp.hiredate);
DBMS_OUTPUT.PUT_LINE('Salary : ' || r_emp.sal);
DBMS_OUTPUT.PUT_LINE('Dept # : ' || r_emp.deptno);
SELECT AVG(sal) INTO v_avgsal
FROM emp WHERE deptno = r_emp.deptno;
IF r_emp.sal > v_avgsal THEN
DBMS_OUTPUT.PUT_LINE('Employee''s salary is more than the department average of '
|| v_avgsal);
ELSE
DBMS_OUTPUT.PUT_LINE('Employee''s salary does not exceed the department average of '
|| v_avgsal);
END IF;
END;