dbixx::row
This class is used for fetching data from single row. It receives the result from dbixx::session or dbixx::result.
General Functions
bool isempty(); dbi_result get_dbi_result()
isempty() checks if the output set of the query was empty.
dbixx::row r
sql<<"SELECT id FROM users WHERE name='nobody'",r;
if(!r.isempty()) { // there is nobody in list!!!
get_dbi_result() returns underlying dbi_result that
allows accessing libdbi features that are not available
from DbiXX Library
Retrieving information about fields
unsigned int cols(); bool isnull(int inx); bool isnull(std::string const &id); bool operator[](int ind); bool operator[](std::string const & id) ;
Function cols() returns number of columns in the row. isnull() returns if specific filed is null, using it's column number (starting from 1) or column name;
bool operator[] is just syntactic sugar for isnull().
For example:
row r;
sql<<"SELECT password "
"FROM users WHERE username=?",name,r;
if(!r.isempty() && r.isnull("password")) {
// login without password
Retrieving actual data
The operation for retrieving the data are following:
bool fetch(int idx,int &value); bool fetch(int idx,unsigned &value); bool fetch(int idx,long long &value); bool fetch(int idx,unsigned long long &value); bool fetch(int idx,double &value); bool fetch(int idx,std::string &value); bool fetch(int idx,std::tm &value); template<typename T> row &operator>>(T &v);
Function fetch, retrieves the value from column idx into value. And returns true if the value is not null.
Operator >> allows fetch data from all columns sequentially starting from column number 1.
For example:
dbixx::row r;
sql<<"SELECT name,age,birthday "
"FROM person WHERE id=?",id;
if(sql.single(r)) {
int age;
string name;
std::tm birth;
r >> name >> age >>birth;
// Do something
}
Automatic Casting
If data type does not mutch, DbiXX tries to cast data to appropriate type, thus you can retrieve double with integer or even string. This is done mostly for "typeless" backends like sqlite3 where strict casting may cause unexpected errors.
If casting fails, dbixx::dbixx_error is thrown.
