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PRO*C中使用動态遊标的四種方法

  PRO*C中使用動态遊标的四種方法

動态方法1

動态方法1的處理過程是先構造一個動态SQL語句然後用EXECUTE IMMEDIATE來執行,EXECUTE IMMEDIATE的功能是分析動态的語句的文本,檢查是否有錯誤,

如果SQL 語句僅執行一次動态方法1的效率很高,動态方法1一定不是SELECT 語句

            1  EXEC SQL EXECUTE IMMEDIATE CREATE TABLE .............;

            2 sprintf(host_string,"");

               EXEC SQL EXECUTE IMMEDIATE :host_string ;

動态方法2

方法2與方法1 類似也是能含有SELECT語句,方法2中含義虛拟輸入宿主變量,比方法1 多了一步SQL語句的文法分析,

 處理方式分為3步:

                構造一個動态SQL

                用PREPARE分析和命名該SQL

                用EXECUTE來執行它

    用法: sprintf(host_string,"DELETE FROM table_name WHERE no=:v1 AND name=:name");(拼帶有輸入宿主變量的SQL)

          EXEC SQL PREPARE sql_name FROM :host_string;(分析文法)

          EXEC SQL EXECUTE IMMEDIATE sql_name USING :v1,:name;(傳遞實際變量)

動态方法3

方法就是使用遊标,查詢并傳回多行,如果在方法1和方法2中的SELECT 語句查詢傳回一行的話,也可以使用SELECT 語句,

方法為 SELECT column1,column2...INTO:variale1,variable2;

方法3是專門解決一次傳回多行的,使用方法:

                                      1  拼成一個 SQL sprintf(host_string,"")

                                      2  用EXEC SQL PREPARE name FROM :host_string 來分析其文法

                                      3  用EXEC SQL DECLARE c_name CURSOR FOR : name 來聲明遊标

                                      4  用EXEC SQL OPEN c_name ;

                                      5  用EXEC SQL FETCH c_name INTO:variable1,:variable2;取出遊标中的資料

                                      6  EXEC SQL CLOSE c_name;關閉遊标

三種動态SQL方法的特點都是先在C語言中拼成所需要的SQL 文本串,然後用EXECUTE IMMEDIATE 來執行

下面是我從網上收集的可以和我的對照,ProC前三種動态SQL的完整示例。

下面是ProC前三種動态SQL的完整示例。

(1)動态SQL1: 不能是查詢(SELECT)語句,并且沒有宿主變量. 

用法:拼一句動态SQL語句,并用EXECUTE IMMEDIATE執行,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)動态SQL2: 不能是查詢(SELECT)語句,并且輸入的宿主變量數目是知道的,

用法:拼一句動态SQL語句,用PREPARE,EXECUTE語句執行.

strcpy(sqlstring, "DELETE FROM test WHERE test_col = :?"); 

EXEC SQL PREPARE sqlproc FROM :sqlstring;

EXEC SQL EXECUTE sqlproc USING :emp_number; 

下文示例中大多數是采用動态SQL2.

(3)動态SQL3: 用于建立動态查詢, 并且要查詢的字段以及輸入的宿主變量數目是知道的

用法: 拼一句動态SQL語句,用PREPARE分析該語句,并要定義一個CURSOR進行取值

如:要查詢的資料在多張表中，select user_name from，可采用動态SQL3來進行查詢

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)

{ 

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也是采用這種方法.

//Proc 示例

#include <stdio.h>
#include <string.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include "sqlca.h"
#include <ctype.h>

//變量，過程預聲明
int i;
char screen[1];
char cmd[1];

//**********************************************************
//CASE對應與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 *);

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

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


//打開資料連接配接
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/[email protected]");
  printf("\n 0:Exit;");
  printf("\n Choose:");

  gets(cmd);
  switch(cmd[0])
  {
   case '1':
    strcpy(oraCN.arr,"workflow/[email protected]");
    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; 
}

//選擇資料操作
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 <The Table Count> ");
    printf("%d",oraCount);
    pause();
    break;

   case '2':
    
    EXEC SQL DECLARE curOne CURSOR FOR SELECT DISTINCT FLOW_NAME FROM CLASS_FLOW WHERE FLOW_CLASS='請假';
    EXEC SQL SELECT COUNT(DISTINCT FLOW_NAME) INTO :oraCount FROM CLASS_FLOW WHERE FLOW_CLASS='請假';
    EXEC SQL OPEN curOne;
    
    for(i=1;i<=oraCount;i++)
    {    
     EXEC SQL FETCH curOne INTO :oraName;
     oraName.arr[oraName.len]='\0';
     printf("\n <Field List> ");
     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 <Fields List> ");
     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 <SQL STATE> ");
    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 <Table Count> ");
    printf("%d",oraCount);
    //dy_tablecount();
    pause();
    break;

   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;

    //接受螢幕資料
    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';


    //組合SELECT語句
    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 <SQL STATE> ");
    printf(oraSql.arr);
    printf("\n");
    //讀取内容
    EXEC SQL PREPARE sqlDy FROM :oraSql;
    EXEC SQL DECLARE curDyField CURSOR FOR sqlDy;
    EXEC SQL OPEN curDyField;


    //組合SELECT COUNT語句
    strcpy(oraCountSql.arr,"SELECT COUNT(*) FROM ");
    strcat(oraCountSql.arr,oraTable.arr);
    oraCountSql.len=strlen(oraCountSql.arr);
    oraCountSql.arr[oraCountSql.len]='\0';
    //讀取數
    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 <Field List> ");
    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;
}
//暫停螢幕
void pause()
{ 
 printf("\n\n--Press Enter To Continue--");
 gets(screen);

}
//顯示意外錯誤
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(); 
}



本文來自CSDN部落格，轉載請标明出處：http://blog.csdn.net/depositpei/archive/2009/02/09/3870424.aspx

本文來自CSDN部落格，轉載請标明出處：http://blog.csdn.net/depositpei/archive/2009/02/09/3870424.aspx

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