sqlplus定义变量区别（替换变量）

5、非PL/SQL变量5.1、替换变量（仅用于SQL *Plus或者用于原理和SQL *Plus相同的开发工具）：
临时存储值
利用它可以达到创建通用脚本的目的
利用它可以达到和用户交互，故在SQL *Plus中又称交互式命令
替换变量的格式式在变量名称前加一个&，以便在运行SQL命令时提示用户输入替换数据，然后按输入数据运行SQL命令
语法：
（1）& ：“&变量名”eg：&name;
生命周期：单次引用中，不需要声明，如果替换字符或日期类型，最好用单引号扩起
使用范围：where、order by、列表达式、表名、整个SELECT 语句中

（2）&& ：“&&变量名”eg：&&name;
生命周期：整个会话（session连接）,不需要声明

（3）define ：“define 变量名=变量值”eg：DEFINE a = clark;
生命周期：整个会话，预先声明，使用时用&引用声明的变量
define variable=用户创建的CHAR类型的值：define 变量名=值；
define column_name(变量名)：查看变量命令。
undefine 变量名：清除变量
define：查看在当前会话中所有的替换变量和它们的值

sqlplus定义变量区别

oracle定义变量（常量）常用：declare、define、variable

1）define、variable用于sqlplus中，在整个sqlplus连接中都生效，而declare用于pl/sql中。

SQL> show user

USER is "TEST"

SQL> var

SP2-0568: No bind variables declared.

SQL> define

DEFINE _DATE           = "20-9月 -10" (CHAR)

DEFINE _CONNECT_IDENTIFIER = "orcl" (CHAR)

DEFINE _USER           = "TEST" (CHAR)

DEFINE _PRIVILEGE      = "" (CHAR)

DEFINE _SQLPLUS_RELEASE = "1002000400" (CHAR)

DEFINE _EDITOR         = "ed" (CHAR)

DEFINE _O_VERSION      = "Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - 64bit Production

With the Partitioning, OLAP, Data Mining and Real Application Testing options" (CHAR)

DEFINE _O_RELEASE      = "1002000400" (CHAR)

SQL> var x number;          ——定义变量x，类型是number

SQL> exec :x:=1;                 ——给变量赋值1

PL/SQL procedure successfully completed.

SQL> print x

         X

----------

         1

SQL> define y='10';

SQL> define

DEFINE _DATE           = "20-9月 -10" (CHAR)

DEFINE _CONNECT_IDENTIFIER = "orcl" (CHAR)

DEFINE _USER           = "TEST" (CHAR)

DEFINE _PRIVILEGE      = "" (CHAR)

DEFINE _SQLPLUS_RELEASE = "1002000400" (CHAR)

DEFINE _EDITOR         = "ed" (CHAR)

DEFINE _O_VERSION      = "Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - 64bit Production

With the Partitioning, OLAP, Data Mining and Real Application Testing options" (CHAR)

DEFINE _O_RELEASE      = "1002000400" (CHAR)

DEFINE Y               = "10" (CHAR)

SQL> disconn

Disconnected from Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - 64bit Production

With the Partitioning, OLAP, Data Mining and Real Application Testing options

SQL> print x

SP2-0640: Not connected

SP2-0641: "PRINT" requires connection to server

SQL> var x

variable   x

datatype   NUMBER

x变量值没了，但是变量定义让然存在

SQL> define

DEFINE _DATE           = "20-9月 -10" (CHAR)

DEFINE _CONNECT_IDENTIFIER = "" (CHAR)

DEFINE _USER           = "" (CHAR)

DEFINE _PRIVILEGE      = "" (CHAR)

DEFINE _SQLPLUS_RELEASE = "1002000400" (CHAR)

DEFINE _EDITOR         = "ed" (CHAR)

DEFINE _O_VERSION      = "Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - 64bit Production

With the Partitioning, OLAP, Data Mining and Real Application Testing options" (CHAR)

DEFINE _O_RELEASE      = "1002000400" (CHAR)

DEFINE Y               = "10" (CHAR)

define定义的y值仍然存在

SQL> show serveroutput

serveroutput OFF

SQL> set serveroutput on

SQL> declare

2 m number :=1;

3 n number;

4 begin

5 select n1 into n from test where rownum=m;

6 dbms_output.put_line(n);

7 end;

8 /

1

PL/SQL procedure successfully completed.

2）variable（var）和define区别在于，前者用于绑定变量，后者是用于&或&&进行变量替换。

SQL> var

SP2-0568: No bind variables declared.

SQL> var x number;

SQL> exec :x:=1;

PL/SQL procedure successfully completed.

SQL> select * from test where rownum=:x;

        N1        N2

---------- ----------

1                    2

SQL> define rn=1;

SQL> define

DEFINE _DATE           = "20-9月 -10" (CHAR)

DEFINE _CONNECT_IDENTIFIER = "orcl" (CHAR)

DEFINE _USER           = "TEST" (CHAR)

DEFINE _PRIVILEGE      = "" (CHAR)

DEFINE _SQLPLUS_RELEASE = "1002000400" (CHAR)

DEFINE _EDITOR         = "ed" (CHAR)

DEFINE _O_VERSION      = "Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - 64bit Production

With the Partitioning, OLAP, Data Mining and Real Application Testing options" (CHAR)

DEFINE _O_RELEASE      = "1002000400" (CHAR)

DEFINE RN              = "1" (CHAR)

SQL> select * from test where rownum=&rn;

old   1: select * from test where rownum=&rn

new   1: select * from test where rownum=1

        N1         N2

---------- ----------

         1          2