[bbk5128]第12集 - Chapter 06- Working with Composite Data Types -01-4998(Record)

The PL/SQL Text Book

《Oracle PL/SQL Programming》

Anchored Declarations

When you anchor a datatype,you tell PL/SQL to set the datatype of your variable based on the datatype of an already defined data structure-another PL/SQL variable,a predefined TYPE or SUBTYPE,a database table,or a specific column in a table.PL/SQL offers two kinds of anchoring:

• Scalar anchoring:use the %TYPE attribute to define you variable based on a table`s column or some other PL/SQL scalar variabe.
• Record anchoring:use the %ROWTYPE attribute to define your record structure based on a table or a predefined PL/SQL explicit curor.
• The anchoring reference  is reserved at the time the code is compiled;there is no runtime overhead to anchoring.
• The anchor also establishes a dependency between the code and the anchored element(the table,cursor,or package containing the variable referenced).Thi meas that if those elements are changed,the code in which the anchoring takes place is marked INVALID.
• When it is recomiled ,the anchor will again be resolved,thereby keeping the code current with the anchored element.

Another %ROWTYPE Attribute Example

SET SERVEROUT ON;

--创建退休表retired_emp
--创建表的时候，不能使用anchoring declaration
/*
CREATE TABLE retired_emps
(
        empno           employees.employee_id%TYPE,
        ename           employees.last_name%TYPE,
        job             employees.job_id$TYPE,
        mgr             employees.manager_id%TYPE,
        hiredate        employees.hire_date%TYPE,
        leavedate       employees.hire_date$TYPE,
        comm            employees.commission_pct%TYPE,
        deptno          employees.department_id%TYPE
);
*/
/*
DROP TABLE retired_emps;

CREATE TABLE retired_emps AS SELECT * FROM employees WHERE 1=2;

ALTER TABLE retired_emps DROP COLUMN FIRST_NAME;
ALTER TABLE retired_emps DROP COLUMN EMAIL;
ALTER TABLE retired_emps DROP COLUMN PHONE_NUMBER;

ALTER TABLE retired_emps ADD LEAVEDATE DATE;
*/
TRUNCATE TABLE retired_emps;

DECLARE
        v_emp_id number := 124;
        v_emp_rec employees%ROWTYPE;
BEGIN
        SELECT * INTO v_emp_rec FROM employees WHERE employee_id = v_emp_id;

        INSERT INTO retired_emps(employee_id,last_name,job_id,manager_id,hire_date,leavedate,salary,commission_pct,department_id)
        VALUES(
                v_emp_rec.employee_id,
                v_emp_rec.last_name,
                v_emp_rec.job_id,
                v_emp_rec.manager_id,
                v_emp_rec.hire_date,
                SYSDATE,
                v_emp_rec.salary,
                v_emp_rec.commission_pct,
                v_emp_rec.department_id
              );

        COMMIT;
　　　　　
　　     --不能添加此查询语句，否则会报错.
　　　　  --SELECT * FROM retired_emps;
END;

/

DROP TABLE retired_emps;
CREATE TABLE retired_emps
(
        EMPNO           NUMBER(4),
        ENAME           VARCHAR2(10),
        JOB             VARCHAR2(9),
        MGR             NUMBER(4),
        HIREDATE        DATE,
        LEAVEDATE       DATE,
        SAL             NUMBER(7,2),
        COMM            NUMBER(7,2),
        DEPTNO          NUMBER(2)
);

DECLARE
        v_employee_number NUMBER := 124;
        v_emp_rec         employees%ROWTYPE;
BEGIN
        SELECT *  INTO v_emp_rec FROM employees WHERE employee_id = v_employee_number;

        INSERT INTO retired_emps(empno,ename,job,mgr,hiredate,leavedate,sal,comm,deptno)
        VALUES  (
                        v_emp_rec.employee_id,
                        v_emp_rec.last_name,
                        v_emp_rec.job_id,
                        v_emp_rec.manager_id,
                        v_emp_rec.hire_date,
                        SYSDATE,
                        v_emp_rec.salary,
                        v_emp_rec.commission_pct,
                        v_emp_rec.department_id
                );
        COMMIT;
END;
/

Inserting a Record by Using %ROWTYPE

DECLARE
        v_employee_number NUMBER := 125;
        v_emp_rec retired_emps%ROWTYPE;
BEGIN
        SELECT employee_id,last_name,job_id,manager_id,hire_date,SYSDATE,salary,commission_pct,department_id INTO v_emp_rec FROM employees
        WHERE employee_id = v_employee_number;

        INSERT INTO retired_emps VALUES v_emp_rec;

        COMMIT;

END;
/

SELECT * FROM retired_emps;

Updating a Row in a Table by Using a Record

SET VERIFY OFF
DECLARE
        v_emp_id        NUMBER := 125;
        v_emp_rec       retired_emps%ROWTYPE;
BEGIN
        SELECT * INTO v_emp_rec FROM retired_emps WHERE empno = v_emp_id;

        v_emp_rec.leavedate := CURRENT_DATE;

        UPDATE retired_emps SET ROW = v_emp_rec WHERE empno = v_emp_id;

        COMMIT;
END;

/

select empno,ename,job,mgr,to_char(hiredate,'YYYY-MM-DD HH24:MI:SS') hiredate,TO_CHAR(leavedate,'YYYY-MM-DD HH24:MI:SS') leavedate from retired_emps;

Record Level Operations

When you work at the record level,you avoid any references to individual fields in the record.Here are the record-level operations currently supported by PL/SQL:

• You can copy the contents of one record to another,as long as they are compatible in structure.
• You can assign a value of NULL to a record with a simple assignment.
• You can define and pass the record as an argument in a parameter list.
• You can RETURN  a record back through the interface of a function.

DECLARE
        v_emp_rec employees%ROWTYPE;
BEGIN
        v_emp_rec := NULL;
END;
/

DROP TABLE cust_sales_roundup;

CREATE TABLE cust_sales_roundup
(
        customer_id     NUMBER(5),
        customer_name   VARCHAR2(100),
        total_sales     NUMBER(15,2)
);

DECLARE
        --基于表的定义Record
        cust_sales_roundup_rec cust_sales_roundup%ROWTYPE;

        CURSOR cust_sales_cur IS SELECT * FROM cust_sales_roundup;
        --基于游标的定义Record
        cust_sales_rec cust_sales_cur%ROWTYPE;

        TYPE customer_sales_rectype IS RECORD
        (
                customer_id     NUMBER(5),
                customer_name   departments.department_name%TYPE,
                total_sales     NUMBER(15,2)
        );
        --基于自定义的Record
        prefererred_cust_rec customer_sales_rectype;
BEGIN
        -- Assign one record to another
        cust_sales_roundup_rec := cust_sales_rec;
        prefererred_cust_rec := cust_sales_rec;
END;
/

基于Anchoring declareation技术，声明Record的不同方法(3种).

You Cannot

Several record-level operations are not yet supported:

• You cannot use the IS NULL syntax to see if all fields in the record have NULL values.Instead,you must apply the IS NULL operator to each field individually.
• You cannot compare two records - for example,you cannot ask if the records(the value of their fields) are same or different,or if one record is greater than or less than another.To answer these kinds of questions,you must compare each individually.

如果要比较两个record是否相等，必须通过r1.column1 == r2.column1,r1.column2 == r2.column2,...

record赋值可以赋NULL，但是不能用IS NULL来判断.

record可以当做参数传递；