sqlplus中define定义的常量和variable定义的变量已经column给变量赋值的区别

前两天看到有人在pub上问在sqlplus中通过define和variable定义,以及column定义的变量的区别。其实define定义的我理解不是变量而是字符常量，通过define定义之后，在通过&或者&&引用的时候不需要输入了，仅此而已。oracle在执行的时候自动用值进行了替换；而variable定义的是绑定变量。

C:>sqlplus xys/manager

SQL*Plus: Release 11.1.0.6.0 - Production on 星期二 4月 1 14:03:00 2008

Copyright (c) 1982, 2007, Oracle. All rights reserved.

连接到:

Oracle Database 11g Enterprise Edition Release 11.1.0.6.0 - Production

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

SQL> define

DEFINE _DATE = "01-4月 -08" (CHAR)

DEFINE _CONNECT_IDENTIFIER = "db11" (CHAR)

DEFINE _USER = "XYS" (CHAR)

DEFINE _PRIVILEGE = "" (CHAR)

DEFINE _SQLPLUS_RELEASE = "1101000600" (CHAR)

DEFINE _EDITOR = "Notepad" (CHAR)

DEFINE _O_VERSION = "Oracle Database 11g Enterprise Edition Release 11.1.0.

6.0 - Production

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

CHAR)

DEFINE _O_RELEASE = "1101000600" (CHAR)

SQL> select *from tt;

ID NAME

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

1 a

2 a

3 "abc"

SQL> define a

SP2-0135: 符号 a 未定义

SQL> define a=1

SQL> define

DEFINE _DATE = "01-4月 -08" (CHAR)

DEFINE _CONNECT_IDENTIFIER = "db11" (CHAR)

DEFINE _USER = "XYS" (CHAR)

DEFINE _PRIVILEGE = "" (CHAR)

DEFINE _SQLPLUS_RELEASE = "1101000600" (CHAR)

DEFINE _EDITOR = "Notepad" (CHAR)

DEFINE _O_VERSION = "Oracle Database 11g Enterprise Edition Release 11.1.0.

6.0 - Production

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

CHAR)

DEFINE _O_RELEASE = "1101000600" (CHAR)

DEFINE A = "1" (CHAR)

--通过上面显示define定义的应该是字符（串）常量。

SQL> select * from tt where id=&a;

原值 1: select * from tt where id=&a

新值 1: select * from tt where id=1

ID NAME

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

1 a

SQL> select * from tt where id=&&a;

原值 1: select * from tt where id=&&a

新值 1: select * from tt where id=1

ID NAME

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

1 a

SQL> define b='a';

SQL> define

DEFINE _DATE = "01-4月 -08" (CHAR)

DEFINE _CONNECT_IDENTIFIER = "db11" (CHAR)

DEFINE _USER = "XYS" (CHAR)

DEFINE _PRIVILEGE = "" (CHAR)

DEFINE _SQLPLUS_RELEASE = "1101000600" (CHAR)

DEFINE _EDITOR = "Notepad" (CHAR)

DEFINE _O_VERSION = "Oracle Database 11g Enterprise Edition Release 11.1.0.

6.0 - Production

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

CHAR)

DEFINE _O_RELEASE = "1101000600" (CHAR)

DEFINE A = "1" (CHAR)

DEFINE B = "a" (CHAR)

--如果是字符类型那么在引用时别忘了加上单引号，另外通过define定义之后在引用时不需要输入了。

SQL> select * from tt where name=&&b;

原值 1: select * from tt where name=&&b

新值 1: select * from tt where name=a

select * from tt where name=a

*

第 1 行出现错误:

ORA-00904: "A": 标识符无效

SQL> select * from tt where name='&&b';

原值 1: select * from tt where name='&&b'

新值 1: select * from tt where name='a'

ID NAME

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

1 a

2 a

SQL> select * from tt where name='&b';

原值 1: select * from tt where name='&b'

新值 1: select * from tt where name='a'

ID NAME

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

1 a

2 a

--执行sql时进行了替换

SQL> select sql_text from v$sql where sql_text like 'select * from tt where name=%';

SQL_TEXT

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

select * from tt where name=1

select * from tt where name='a'

SQL>

--==============================================

--variable定义的是绑定变量

SQL> variable a number;

SQL> print a;

A

----------

SQL> exec :a:=1;

PL/SQL 过程已成功完成。

SQL> select * from tt where id=:a;

ID NAME

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

1 a

SQL> select sql_text from v$sql where sql_text like 'select * from tt where id=:a%';

SQL_TEXT

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

select * from tt where id=:a

SQL> print a;

A

----------

1

column定义:column colvar NEW_VALUE sqlvar,告诉sqlplus 取得colvar列中的值,并将这个值赋给替换变量sqlvar.

SQL> column colvar NEW_VALUE sqlvar;

SQL> select 'val' colvar from dual; -- sqlvar的值被赋值为val.

COL

---

val

SQL> select '&sqlvar' xxx from dual; --可以看到sqlvar的值为val.

old   1: select '&sqlvar' xxx from dual

new   1: select 'val' xxx from dual

XXX

---

val

通常用来设置SQL提示符的方法:

SQL> column global_name new_value gname;

SQL> select lower(user) || '@' || substr ( global_name,1,

decode (dot,0,length(global_name), dot-1)) global_name

from (select global_name,instr(global_name,'.')dot from global_name );

set sqlprompt '&gname>';
plsql@ORCL>

在http://warehouse.itpub.net/post/777/458719的基础上加了column的用法