ANSI动态SQL

ANSI 动态SQL是在Oracle 8i之后开始有的，以前用的时候用的是Oracle动态SQL方法四（下篇文章），ANSI动态 SQL实现了宿主变量和选择

列表变量在未知情况下的处理，也就是等号的左右 ，现在都可以实现动态的指定了。

ANSI动态SQL的步骤如下：

1，分配输入描述区和分配输出描述区

2，准备SQL语句并定义游标

3，处理绑定变量

4，打开游标

5，处理查询结果

6，释放描述区，关闭游标

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <sqlca.h>
void connect();
void sql_err();
void process_input();
void process_output();
EXEC SQL BEGIN DECLARE SECTION;
     char sql_stat[100];
EXEC SQL END DECLARE SECTION;
void main()
{
   EXEC SQL WHENEVER SQLERROR  DO sql_err();
   connect();
   EXEC SQL ALLOCATE DESCRIPTOR 'input_descriptor';
   EXEC SQL ALLOCATE DESCRIPTOR 'output_descriptor';
   for(;;)
   {
      printf("input ANSI dynamic sql_statement(X:to exit): \n");
      gets(sql_stat);
      if((strncmp(sql_stat,"X",1)==0)||(strncmp(sql_stat,"x",1)==0)) break;
      EXEC SQL PREPARE S FROM :sql_stat;
      EXEC SQL DECLARE C CURSOR FOR S;
      process_input();
      EXEC SQL OPEN C USING DESCRIPTOR 'input_descriptor';
      if((strncmp(sql_stat,"SELECT",6)==0)||(strncmp(sql_stat,"select",6)==0))
         process_output();
     EXEC SQL CLOSE C;
   }
   EXEC SQL DEALLOCATE DESCRIPTOR 'input_descriptor';
   EXEC SQL DEALLOCATE DESCRIPTOR 'output_descripotr';
   EXEC SQL COMMIT WORK RELEASE;
   puts("\n thanks for using ANSI dynamic sql\n");
}

void sql_err()
{
  printf ("%.*s\n",sqlca.sqlerrm.sqlerrml,sqlca.sqlerrm.sqlerrmc);
}
void connect()
{
  EXEC SQL BEGIN DECLARE SECTION;
  char username[20],password[20];
  EXEC SQL END DECLARE SECTION;
  printf("input username: ");
  gets(username);
  printf("input password: ");
  gets(password);
  EXEC SQL CONNECT :username IDENTIFIED BY :password;
}

void process_input()
{
    EXEC SQL BEGIN DECLARE SECTION;
      int i;
      char name[31];
      int input_count,input_len,occurs,ANSI_varchar_type;
      char input_buf[200];
    EXEC SQL END DECLARE SECTION;
    EXEC SQL DESCRIBE INPUT S USING DESCRIPTOR 'input_descriptor';
    EXEC SQL GET DESCRIPTOR 'input_descriptor' :input_count=COUNT;
    ANSI_varchar_type=12;
    for(i=0;i<input_count;i++)
    {
       occurs=i+1;
       EXEC SQL GET DESCRIPTOR 'input_descriptor' VALUE :occurs :name = NAME;
       printf ("\ninput value for %s: ",name);
       gets(input_buf);
       input_len=strlen(input_buf);
       input_buf[input_len]='\0';
       EXEC SQL SET DESCRIPTOR 'input_descriptor'
            VALUE :occurs TYPE = :ANSI_varchar_type,
            LENGTH = :input_len,DATA = :input_buf;
    }
}

void process_output()
{
    EXEC SQL BEGIN DECLARE SECTION;
       int i;
       int output_count,occurs,type,len;
       short indi;
       char data[200],name[31];
    EXEC SQL END DECLARE SECTION;
    EXEC SQL DESCRIBE OUTPUT S USING DESCRIPTOR 'output_descriptor';
    EXEC SQL GET DESCRIPTOR 'output_descriptor' :output_count = COUNT;
    printf ("\n");
    type = 12;
    len =200;
    for (i = 0; i < output_count; i++)
    {
       occurs = i + 1;
       EXEC SQL SET DESCRIPTOR 'output_descriptor' VALUE :occurs TYPE = :type,LENGTH = :len;
       EXEC SQL GET DESCRIPTOR 'output_descriptor' VALUE :occurs :name = NAME;
       printf ("\t%s ",name);
    }
    EXEC SQL WHENEVER NOT FOUND DO sql_err();
    for(;;)
    {
       EXEC SQL FETCH C INTO DESCRIPTOR 'output_descriptor';
       for(i = 0; i < output_count; i++)
       {
          occurs = i + 1;
          EXEC SQL GET DESCRIPTOR 'output_descriptor' VALUE :occurs :data = DATA, :indi = INDICATOR;
          if(indi == -1)
            printf ("\t%s "," ");
          else
            printf ("\t%s ",data);
       }
     printf ("\n");
    }
}