DatabaseReadBind
移动到下一条记录，并从中将数据读入结构。
bool DatabaseReadBind(
int request, //DatabasePrepare中创建的请求句柄
void& struct_object //对读取记录结构的引用
);参数
request
[in] DatabasePrepare()中创建的请求句柄。
struct_object
[out] 要读入当前记录中数据的结构的引用。该结构应该只有数值类型和/或字符串（不允许数组）作为成员，并且不能是衍生体。
返回值
如果成功返回true，否则返回false。要获得错误代码，请使用GetLastError()，可能回应：
- ERR_INVALID_PARAMETER (4003) – 没有指定表格名称（空字符串或NULL）；
- ERR_WRONG_STRING_PARAMETER (5040) – 将请求转换为UTF-8字符串时出现错误；
- ERR_DATABASE_INTERNAL (5120) – 内部数据库错误；
- ERR_DATABASE_INVALID_HANDLE (5121) – 内部数据库句柄；
- ERR_DATABASE_EXECUTE (5124) – 请求执行错误；
- ERR_DATABASE_NO_MORE_DATA (5126) – 不存在表格（没有错误，正常完成）。
注意
struct_object结构中的字段数不应超过DatabaseColumnsCount()。如果struct_object结构中的字段数小于记录中的字段数，则执行部分读取。使用相应的DatabaseColumnText()、 DatabaseColumnInteger()等函数可以明确获取剩余的数据。
示例：
struct Person
{
int id;
string name;
int age;
string address;
double salary;
};
//+------------------------------------------------------------------+
//| Script program start function |
//+------------------------------------------------------------------+
void OnStart()
{
int db;
string filename="company.sqlite";
//--- open
db=DatabaseOpen(filename, DATABASE_OPEN_READWRITE | DATABASE_OPEN_CREATE |DATABASE_OPEN_COMMON);
if(db==INVALID_HANDLE)
{
Print("DB: ", filename, " open failed with code ", GetLastError());
return;
}
//--- if the table COMPANY exists then drop the table
if(DatabaseTableExists(db, "COMPANY"))
{
//--- delete the table
if(!DatabaseExecute(db, "DROP TABLE COMPANY"))
{
Print("Failed to drop table COMPANY with code ", GetLastError());
DatabaseClose(db);
return;
}
}
//--- create table
if(!DatabaseExecute(db, "CREATE TABLE COMPANY("
"ID INT PRIMARY KEY NOT NULL,"
"NAME TEXT NOT NULL,"
"AGE INT NOT NULL,"
"ADDRESS CHAR(50),"
"SALARY REAL );"))
{
Print("DB: ", filename, " create table failed with code ", GetLastError());
DatabaseClose(db);
return;
}
//--- insert data
if(!DatabaseExecute(db, "INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) VALUES (1, 'Paul', 32, 'California', 25000.00 ); "
"INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) VALUES (2, 'Allen', 25, 'Texas', 15000.00 ); "
"INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) VALUES (3, 'Teddy', 23, 'Norway', 20000.00 );"
"INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) VALUES (4, 'Mark', 25, 'Rich-Mond ', 65000.00 );"))
{
Print("DB: ", filename, " insert failed with code ", GetLastError());
DatabaseClose(db);
return;
}
//--- prepare the request
int request=DatabasePrepare(db, "SELECT * FROM COMPANY WHERE SALARY>15000");
if(request==INVALID_HANDLE)
{
Print("DB: ", filename, " request failed with code ", GetLastError());
DatabaseClose(db);
return;
}
//--- print records
Person person;
Print("Persons with salary > 15000:");
for(int i=0; DatabaseReadBind(request, person); i++)
Print(i, ": ", person.id, " ", person.name, " ", person.age, " ", person.address, " ", person.salary);
//--- delete request after use
DatabaseFinalize(request);
Print("Some statistics:");
//--- prepare new request about total salary
request=DatabasePrepare(db, "SELECT SUM(SALARY) FROM COMPANY");
if(request==INVALID_HANDLE)
{
Print("DB: ", filename, " request failed with code ", GetLastError());
DatabaseClose(db);
return;
}
while(DatabaseRead(request))
{
double total_salary;
DatabaseColumnDouble(request, 0, total_salary);
Print("Total salary=", total_salary);
}
//--- delete request after use
DatabaseFinalize(request);
//--- prepare new request about average salary
request=DatabasePrepare(db, "SELECT AVG(SALARY) FROM COMPANY");
if(request==INVALID_HANDLE)
{
Print("DB: ", filename, " request failed with code ", GetLastError());
ResetLastError();
DatabaseClose(db);
return;
}
while(DatabaseRead(request))
{
double aver_salary;
DatabaseColumnDouble(request, 0, aver_salary);
Print("Average salary=", aver_salary);
}
//--- delete request after use
DatabaseFinalize(request);
//--- close database
DatabaseClose(db);
}
//+-------------------------------------------------------------------
/*
Output:
Persons with salary > 15000:
0: 1 Paul 32 California 25000.0
1: 3 Teddy 23 Norway 20000.0
2: 4 Mark 25 Rich-Mond 65000.0
Some statistics:
Total salary=125000.0
Average salary=31250.0
*/