自学PL/SQL 第三讲Interacting with the Oracle Server

本讲课程目标

1.在PL/SQL块中执行select语句

2.在PL/SQL块中执行DML语句和控制事务

3.使用隐式游标定义PL/SQL块中DML语句的输出

在PL/SQL块中"END；"表示结束PL/SQL块，但并没有结束事务，一个块可以跨越多个事务，一个事务也可以跨越多个块；PL/SQL块中不支持DDL和DCL语句，例如建表，赋予用户权限等.

一：在PL/SQL块中执行select语句

select语句在PL/SQL块中的语法结构如下

SELECT select_list

INTO {variable_name[, variable_name]...

| record_name}

FROM table

[WHERE condition];

范例：

SQL> set serveroutput on
SQL> DECLARE
2      v_first_name hr.employees.first_name%TYPE;
3      v_last_name  hr.employees.last_name%TYPE;
4  BEGIN
5     SELECT first_name,last_name INTO
6     v_first_name,v_last_name FROM hr.employees
7     WHERE employee_id=100;
8     DBMS_OUTPUT.PUT_LINE(v_first_name ||' '||v_last_name);
9* END;

SQL> /
Steven King
PL/SQL procedure successfully completed

二.在PL/SQL块中执行DML语句和控制事务

可以在PL/SQL块中使用SQL的函数，自定义的序列号，字段的默认值插入数据

SQL> create table t14703a (id number(5),constraint pk_t14703a primary key(id),
2   location varchar2(30) default 'fuzhou',salary number(8,2));
Table created.

SQL> create sequence user_seq
2  increment by 1
3  start with 1
4  maxvalue 99999
5  nocache
6* nocycle
Sequence created.

SQL> select user_seq.nextval from dual;

NEXTVAL
----------
1

SQL> BEGIN
2   INSERT INTO hr.t14703a
3   (id,location,salary) VALUES
4   (user_seq.nextval,default,'6000');
5  COMMIT;
6* END;
SQL> /
PL/SQL procedure successfully completed.

SQL> select * from hr.t14703a;

ID LOCATION       SALARY
---------- ---------- ----------
3 fuzhou           6000

SQL> DECLARE
2       v_salary_increase hr.t14703a.salary%TYPE := 500;
3    BEGIN
4        UPDATE hr.t14703a SET salarysalary= salary + v_salary_increase
5        WHERE id=3;
6*   END;
7  /
PL/SQL procedure successfully completed.

SQL> select * from hr.t14703a;

ID LOCATION       SALARY
---------- ---------- ----------
3 fuzhou           6500

三.使用隐式游标定义PL/SQL块中DML语句的输出

SQL游标，游标是私有的SQL工作区，有隐式和显式游标两个类型；oracle server使用隐式的游标来执行SQL语句

A cursor is a private SQL work area.

There are two types of cursors:

– Implicit cursors

– Explicit cursors

The Oracle server uses implicit cursors to parse and execute your SQL statements.

Explicit cursors are explicitly declared by the programmer.

4种游标的属性SQL%COUNT,SQL%FOUND,SQL%NOTFOUND,SQL%ISOPEN

SQL> VAR rownums varchar2(30)
SQL> set serveroutput on
SQL> DECLARE
2     v_a  hr.t04310_a.a%TYPE := 50000;
3   BEGIN
4     delete  from  hr.t04310_a where a < v_a;
5     :rownums := (SQL%ROWCOUNT ||' ' || 'row deleted');
6     DBMS_OUTPUT.PUT_LINE(:rownums);
7*  END;
8  /
40000 row deleted
PL/SQL procedure successfully completed.

本文出自 “斩月” 博客，谢绝转载！