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