PRO*C中使用动态游标的四种方法 

动态方法1
动态方法1的处理过程是先构造一个动态SQL语句然后用EXECUTE IMMEDIATE来执行,EXECUTE IMMEDIATE的功能是分析动态的语句的文本,检查是否有错误,
如果SQL 语句仅执行一次动态方法1的效率很高,动态方法1一定不是SELECT 语句
            1  EXEC SQL EXECUTE IMMEDIATE CREATE TABLE .............;
           
            2 sprintf(host_string,"");
               EXEC SQL EXECUTE IMMEDIATE :host_string ;
动态方法2
方法2与方法1 类似也是能含有SELECT语句,方法2中含义虚拟输入宿主变量,比方法1 多了一步SQL语句的语法分析,
 处理方式分为3步:
                构造一个动态SQL
                用PREPARE分析和命名该SQL
                用EXECUTE来执行它
    用法: sprintf(host_string,"DELETE FROM table_name WHERE no=:v1 AND name=:name");(拼带有输入宿主变量的SQL)
          EXEC SQL PREPARE sql_name FROM :host_string;(分析语法)
          EXEC SQL EXECUTE IMMEDIATE sql_name USING :v1,:name;(传递实际变量)
         
动态方法3
方法就是使用游标,查询并返回多行,如果在方法1和方法2中的SELECT 语句查询返回一行的话,也可以使用SELECT 语句,
方法为 SELECT column1,column2...INTO:variale1,variable2;
方法3是专门解决一次返回多行的,使用方法:
                                      1  拼成一个 SQL sprintf(host_string,"")
                                      2  用EXEC SQL PREPARE name FROM :host_string 来分析其语法
                                      3  用EXEC SQL DECLARE c_name CURSOR FOR : name 来声明游标
                                      4  用EXEC SQL OPEN c_name ;
                                      5  用EXEC SQL FETCH c_name INTO:variable1,:variable2;取出游标中的数据
                                      6  EXEC SQL CLOSE c_name;关闭游标
         
三种动态SQL方法的特点都是先在C语言中拼成所需要的SQL 文本串,然后用EXECUTE IMMEDIATE 来执行

下面是我从网上收集的可以和我的对照,ProC前三种动态SQL的完整示例。

ProC动态SQL示例(第1,2,3种方法)

草木瓜 2006-2-1

下面是ProC前三种动态SQL的完整示例。

(1)动态SQL1: 不能是查询(SELECT)语句,并且没有宿主变量. 
用法:拼一句动态SQL语句,并用EXECUTE IMMEDIATE执行,如:
 
EXEC SQL EXECUTE IMMEDIATE CREATE TABLE test (test_col VARCHAR2(4));
EXEC SQL EXECUTE IMMEDIATE INSERT INTO TABLE test ('AAAA');
EXEC SQL EXECUTE IMMEDIATE DELETE test WHERE test_col='AAAA';

(2)动态SQL2: 不能是查询(SELECT)语句,并且输入的宿主变量数目是知道的,
用法:拼一句动态SQL语句,用PREPARE,EXECUTE语句执行.
strcpy(sqlstring, "DELETE FROM test WHERE test_col = :?"); 
EXEC SQL PREPARE sqlproc FROM :sqlstring;
EXEC SQL EXECUTE sqlproc USING :emp_number; 
 
下文示例中大多数是采用动态SQL2.
 
(3)动态SQL3: 用于创建动态查询, 并且要查询的字段以及输入的宿主变量数目是知道的
用法: 拼一句动态SQL语句,用PREPARE分析该语句,并要定义一个CURSOR进行取值
如:要查询的数据在多张表中，select user_name from，可采用动态SQL3来进行查询
strcpy(sql,"select user_name from ");
strcat(sql,"table1");//table2,table3,table4
EXEC SQL PREPARE sqlproc FROM :sql;
EXEC SQL DECLARE cur_user_name CURSOR FOR sqlproc;
EXEC SQL OPEN cur_user_name;
while(1)
{ 
EXEC SQL FETCH cur_user_name into :ora_id;
if (sqlca.sqlcode < 0)
{ 
/*FETCH CURSOR失败*/ 
printf("fetch cursor fail,sqlcode=%ld,sqlserr=%s",sqlca.sqlcode,sqlca.sqlerrm.sqlerrmc);
}
if( sqlca.sqlcode == SQLNOTFOUND)
{
break;
}
}
EXEC SQL CLOSE cur_user_name; 

下文示例中Case5也是采用这种方法.

//Proc 示例

#include
#include
#include
#include
#include
#include "sqlca.h"
#include

//变量，过程预声明
int i;
char screen[1];
char cmd[1];

//**********************************************************
//CASE对应与db_selectop的switch
EXEC SQL BEGIN DECLARE SECTION;

VARCHAR oraName[30];    //CASE 1,2,3

VARCHAR oraValue[20];    //CASE 1,2,3,5
int oraCount;          //CASE 1,2,3,4,5
VARCHAR oraSql[30],oraTable[20]; //CASE 4,5

VARCHAR oraField[10];    //CASE 5
VARCHAR oraCountSql[30];   //CASE 5

VARCHAR oraCode[10];    //CASE 6
VARCHAR oraContent[10];    //CASE 6

EXEC SQL END DECLARE SECTION;
//**********************************************************

int db_connect();
int db_selectop();

//void dy_tablecount();
//void dy_tablefield();
void view_tabledata();

void pause();
void sql_error(char *);

//主函数
void main()
{
 EXEC SQL INCLUDE sqlca;
 EXEC ORACLE OPTION (RELEASE_CURSOR = YES);
 EXEC SQL WHENEVER SQLERROR DO sql_error(" ");

 if(db_connect()==0)
 {
  db_selectop();
 }
}

//打开数据连接
int db_connect()
{  

 EXEC SQL BEGIN DECLARE SECTION;
 VARCHAR oraCN[30];
 EXEC SQL END DECLARE SECTION;

 printf("----------------------------------");
 printf("\n [ Examples With Oracle DB  ]\n");
 printf("----------------------------------");
 printf("\n                   Designed by Liwei 2005\n");
 cmd[0]='A';
 while(cmd[0]!='0' && cmd[0]!='1')
 {

  printf("\n Confirm DB Source:");
  printf("\n 1:workflow/workflow@if");
  printf("\n 0:Exit;");
  printf("\n Choose:");

  gets(cmd);
  switch(cmd[0])
  {
   case '1':
    strcpy(oraCN.arr,"workflow/workflow@if");
    oraCN.len = strlen(oraCN.arr);
    oraCN.arr[oraCN.len]='\0';

    //EXEC SQL WHENEVER SQLERROR GOTO cnError;
    EXEC SQL CONNECT :oraCN;
    
    printf("\n [OK Connected!] ");
    return 0;

   
    break;
   case '0':
    break;
   default:
    printf("\n [Error Input!] \n");
    break;
  }
 
 }

 
 exit(0);

//cnError:
// printf("\n [Error Oracle Connected!]");
// return 1; 
}

//选择数据操作
int db_selectop()
{
 char order[1];

 cmd[0]='A';
 //order[0]='A';

 while(cmd[0]!='0')
 {
  printf("\n ");
  printf("\n Select DB Method:");
  printf("\n -------------------------------------------");
  printf("\n 1: GetTableCount      STATIC [CLASS_FLOW]");
  printf("\n 2: GetTableField One  STATIC [CLASS_FLOW]");
  printf("\n 3: GetTableField Muti STATIC [USE_POWER]");
  printf("\n");
  printf("\n 4: GetTableCount      DYNAMIC      ");
  printf("\n 5: GetTableField One  DYNAMIC      ");
  printf("\n");
  printf("\n 6: EditTable USE_DEPT");
  printf("\n -------------------------------------------");
  printf("\n 0: Exit");
  printf("\n\n Enter:");

  gets(cmd);

  switch(cmd[0])
  {
   case '1':
    
    EXEC SQL SELECT NVL(COUNT(*),0) INTO :oraCount FROM CLASS_FLOW;
    
    printf("\n ");
    printf("%d",oraCount);
    pause();
    break;

   case '2':
    
    EXEC SQL DECLARE curOne CURSOR FOR SELECT DISTINCT FLOW_NAME FROM CLASS_FLOW WHERE FLOW_CLASS='请假';
    EXEC SQL SELECT COUNT(DISTINCT FLOW_NAME) INTO :oraCount FROM CLASS_FLOW WHERE FLOW_CLASS='请假';
    EXEC SQL OPEN curOne;
    
    for(i=1;i<=oraCount;i++)
    {    
     EXEC SQL FETCH curOne INTO :oraName;
     oraName.arr[oraName.len]='\0';
     printf("\n ");
     printf("%s",oraName.arr);
    }
    EXEC SQL CLOSE curOne;
    pause();
    break;

   case '3':

    EXEC SQL DECLARE curMuti CURSOR FOR SELECT POWER_ID,POWER_NAME FROM USE_POWER ORDER BY POWER_ID ASC;
    EXEC SQL SELECT COUNT(*) INTO :oraCount FROM USE_POWER;
    EXEC SQL OPEN curMuti;
    
    for(i=1;i<=oraCount;i++)
    {    
     EXEC SQL FETCH curMuti INTO :oraValue,:oraName;
     oraValue.arr[oraValue.len]='\0';
     oraName.arr[oraName.len]='\0';
     printf("\n ");
     printf("%-8s",oraValue.arr);
     printf("%-20s",oraName.arr);
    }

    EXEC SQL CLOSE curMuti;

    pause();
    break;

   case '4':

    //EXEC SQL BEGIN DECLARE SECTION;
    //VARCHAR oraSql[30],oraTable[20];
    //int oraCount;
    //EXEC SQL END DECLARE SECTION;

    printf("\n Custom Table ");
    printf("\n ----------------------- ");
    printf("\n Input Table Name:");
    gets(oraTable.arr);

    oraTable.len=strlen(oraTable.arr);
    oraTable.arr[oraTable.len]='\0';

    strcpy(oraSql.arr,"SELECT COUNT(*) FROM ");
    strcat(oraSql.arr,oraTable.arr);
    oraSql.len=strlen(oraSql.arr);
    oraSql.arr[oraSql.len]='\0';

    printf("\n ");
    printf(oraSql.arr);
    printf("\n ");

    EXEC SQL PREPARE sqlDyCount FROM :oraSql;
    EXEC SQL DECLARE curDyCount CURSOR FOR sqlDyCount;
    EXEC SQL OPEN curDyCount;
    EXEC SQL FETCH curDyCount INTO :oraCount;
    EXEC SQL CLOSE curDyCount;

    printf("\n

   case '5':

    //EXEC SQL BEGIN DECLARE SECTION;
    //VARCHAR oraSql[30],oraTable[10],oraField[10],oraValue[20];
    //VARCHAR oraCountSql[30];
    //int oraCount;
    //EXEC SQL END DECLARE SECTION;

    //接受屏幕数据
    printf("\n Custom Table And Field ");
    printf("\n ----------------------- ");
    printf("\n Input Table Name:");
    gets(oraTable.arr);
    oraTable.len=strlen(oraTable.arr);
    oraTable.arr[oraTable.len]='\0';
    printf(" Input Field Name:");
    gets(oraField.arr);
    oraField.len=strlen(oraField.arr);
    oraField.arr[oraField.len]='\0';

    //组合SELECT语句
    strcpy(oraSql.arr,"SELECT ");
    strcat(oraSql.arr,oraField.arr);
    strcat(oraSql.arr," FROM ");
    strcat(oraSql.arr,oraTable.arr);
    oraSql.len=strlen(oraSql.arr);
    oraSql.arr[oraSql.len]='\0';
    printf("\n ");
    printf(oraSql.arr);
    printf("\n");
    //读取内容
    EXEC SQL PREPARE sqlDy FROM :oraSql;
    EXEC SQL DECLARE curDyField CURSOR FOR sqlDy;
    EXEC SQL OPEN curDyField;

    //组合SELECT COUNT语句
    strcpy(oraCountSql.arr,"SELECT COUNT(*) FROM ");
    strcat(oraCountSql.arr,oraTable.arr);
    oraCountSql.len=strlen(oraCountSql.arr);
    oraCountSql.arr[oraCountSql.len]='\0';
    //读取数
    EXEC SQL PREPARE sqlDyCount FROM :oraCountSql;
    EXEC SQL DECLARE curDyFieldCount CURSOR FOR sqlDyCount;
    EXEC SQL OPEN curDyFieldCount;
    EXEC SQL FETCH curDyFieldCount INTO :oraCount;

    for(i=1;i<=oraCount;i++)
    {
    EXEC SQL FETCH curDyField INTO :oraValue;
    oraValue.arr[oraValue.len]='\0';
    printf("\n ");
    printf("%s",oraValue.arr);
    }
    EXEC SQL CLOSE curDyFieldCount;
    EXEC SQL CLOSE curDyField;
    //dy_tablefield();
    pause();
    break;

   case '6':

    order[0]='A';
    while(order[0]!='0')
    {
     printf("\n ");
     printf("\n Edit Table ");
     printf("\n -------------");
     printf("\n 1: VIEW");
     printf("\n 2: INSERT");
     printf("\n 3: DELETE");
     printf("\n 4: UPDATE");
     printf("\n -------------");
     printf("\n 0: EXIT");
     printf("\n\n Enter:");
     gets(order);

     switch(order[0])
     {
     case '1':
      view_tabledata();
      pause();
      break;
     case '2':
      //INSERT
      printf("\n INSERT ");
      printf("\n ----------------------- ");
      printf("\n ENTER CODE:");
      gets(oraCode.arr);
      oraCode.len=strlen(oraCode.arr);
      oraCode.arr[oraCode.len]='\0';
      printf(" ENTER CONTENT:");
      gets(oraContent.arr);
      oraContent.len=strlen(oraContent.arr);
      oraContent.arr[oraContent.len]='\0';

      EXEC SQL INSERT INTO USE_DEPT VALUES(:oraCode,:oraContent);
      EXEC SQL COMMIT;
      pause();
      break;
     case '3':
      view_tabledata();
      //DELETE
      printf("\n DELETE ");
      printf("\n ----------------------- ");
      printf("\n ENTER CODE:");
      gets(oraCode.arr);
      oraCode.len=strlen(oraCode.arr);
      oraCode.arr[oraCode.len]='\0';
      EXEC SQL DELETE USE_DEPT WHERE DEPT_ID=:oraCode;
      EXEC SQL COMMIT;
      //strcpy(c_sql, "DELETE FROM EMP WHERE EMPNO = :?"); 
      //EXEC SQL PREPARE sql_stmt FROM :c_sql;
      //EXEC SQL EXECUTE sql_stmt USING :emp_number; 
      pause();
      break;
     case '4':
      view_tabledata();
      //UPDATE
      printf("\n UPDATE ");
      printf("\n ----------------------- ");
      printf("\n ENTER CODE:");
      gets(oraCode.arr);
      oraCode.len=strlen(oraCode.arr);
      oraCode.arr[oraCode.len]='\0';
      printf(" ENTER CONTENT:");
      gets(oraContent.arr);
      oraContent.len=strlen(oraContent.arr);
      oraContent.arr[oraContent.len]='\0';

      EXEC SQL UPDATE USE_DEPT SET DEPT_NAME=:oraContent WHERE DEPT_ID=:oraCode;
      EXEC SQL COMMIT;

      pause();
      break;
     default:
      break;
     }
    }
    cmd[0]='6';
    break; 

   default:
    break;
  }

 
 }
 return 0;

}

void view_tabledata()
{
 //VIEW
 EXEC SQL DECLARE curTable CURSOR FOR SELECT DEPT_ID,DEPT_NAME FROM USE_DEPT ORDER BY DEPT_ID ASC;
 EXEC SQL SELECT COUNT(*) INTO :oraCount FROM USE_DEPT;
 EXEC SQL OPEN curTable;

 printf("\n  ");
 printf("%-8s","CODE");
 printf("%-20s","CONTENT");
 printf("\n--------------------");

 for(i=1;i<=oraCount;i++)
 {    
  EXEC SQL FETCH curTable INTO :oraValue,:oraName;
  oraValue.arr[oraValue.len]='\0';
  oraName.arr[oraName.len]='\0';
  printf("\n ");
  printf("%-8s",oraValue.arr);
  printf("%-20s",oraName.arr);
 }

 printf("\n--------------------");

 EXEC SQL CLOSE curTable;
}
//暂停屏幕
void pause()
{ 
 printf("\n\n--Press Enter To Continue--");
 gets(screen);

}
//显示意外错误
void sql_error(char *msg)
{
 //printf("\n%s %ld %s\n", msg,sqlca.sqlcode,(char *)sqlca.sqlerrm.sqlerrmc);
 printf("\n%s %s\n", msg,(char *)sqlca.sqlerrm.sqlerrmc);
 //EXEC SQL ROLLBACK RELEASE;
 db_selectop();
}