PL/SQL ѧϰ±Ê¼Ç3

 SQL> var a number
SQL> begin
2 :a :=1000;
3 end;
4 /
PL/SQL procedure successfully completed.
SQL> edit
Wrote file afiedt.buf
1 begin
2 dbms_output.put_line(:a);
3* end;
SQL> /
ͨ¹ýÕâ¸ö´úÂë¿ÉÒÔ¿´³öͨ¹ýpl/sql³õʼ»¯¸³ÖµµÄBind variable¿ÉÒÔ±»ÆäËûPl/sql³ÌÐòµ÷ÓÃ
%type ÀàÐÍÓ¦ÓõĻ° Èç¹ûÇ°ÃæÓõÄÊÇdatabase columnµÄ»° ÄÇô²»¿ÉÒÔ¼Ónot null,Ç°ÃæÒýÓõÄÊÇÉùÃ÷µÄ±äÁ¿¿ÉÒÔÓ¦ÓÃnot null
A NOT NULLdatabase column constraint does not apply to variables that are declared using %TYPE.  
Therefore, if you declare a variable using the %TYPEattribute that uses a database column defined as NOT  
NULL, you can assign the NULLvalue to the variable.  
eg:
°ó¶¨±äÁ¿
A bind variable is a variable that you declare in a host environment.
 Bind variables can be used to pass run-time values, either number or character, into or out of one or more PL/SQL programs. The PL/SQL  
programs use bind variables as they would use any other variable. You can reference variables declared in the  
host or calling environment in PL/SQL statements, unless the statement is in a procedure, function, or  
package. This includes host language variables declared in precompiler programs, screen fields in Oracle   Developer Forms applications, and iSQL*Plus bind variables.
°ó¶¨±äÁ¿¿ÉÒÔÔÚÖ÷»ú»·¾³ÏÂÉùÃ÷ ¿ÉÒÔÔÚsqlplus ÕâÖÖÓ¦ÓóÌÐòÏÂÉùÃ÷ È»ºópl/sql³ÌÐòÀ´µ÷Óà µ÷ÓÃÐèÒªÔڸñäÁ¿Ç°¼Ócolon
¸³ÖµµÄʱºò¿ÉÒÔʹÓà exec :var_name := 10000; or begin :var_name := 1000 end; »òÕßÊÇÔÚPL/SQLÖи³Öµ
print(sqlplus command)¿ÉÒÔ´òÓ¡³öÕâ¸öÖµ
SQL> var result number
SQL> begin
2 select (sal*12) + nvl(comm,0)
3 into :result
4 from emp
5 where empno = 7369;
6 end;
7 /
PL/SQL procedure successfully completed.
SQL> print result
RESULT
------
9600
SQL> exec :result = 10000
BEGIN :result = 10000; END;
*
ERROR at line 1:
ORA-06550: line 1, column 15:
PLS