pro*c 里怎么将select 的返回内容赋值给变量

pro*c 里怎么将select 的返回内容赋值给变量

EXEC SQL BEGIN DECLARE SECTION;
      char CALLNO[30];
  EXEC SQL END DECLARE SECTION;

 
  EXEC SQL SELECT CALLNO INTO :CALLNO from out_call;
  EXEC SQL COMMIT WORK RELEASE;
 
  printf("CALLNO = %s\n intCALLNO = %d\n",CALLNO,intCALLNO);


打印结果为空，是为啥？

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这个查询是一个结果还是多个结果,如果多个结果请使用游标,如果一个结果这句话没什么问题.
1.输出为一个结果的
exec sql begin declare section;
CS_CHAR id[6];
CS_SMALLINT indic;
CS_CHAR pub_name[41];
exec sql end declare section;
exec sql select pub_id into :id indicator :indic
from titles where title
like "%Stress%";
if (indic == -1)
{
printf("\npub_id is null");
}
else
{
exec sql select pub_name into :pub_name
from publishers where pub_id = :id;
printf("\nPublisher: %s", pub_name);
}

2输出为多个结果的
EXEC SQL DECLARE C1 CURSOR FOR
SELECT id, name, dept, job, years, salary, comm from staff;
EXEC SQL OPEN c1;
while (SQLCODE == 0)
{
EXEC SQL FETCH c1 INTO :id, :name, :dept, :job, :years, :salary, :comm;
if (SQLCODE == 0)
printf("%4d %12s %10d %10s %2d %8d %8d",
id, name, dept, job