Qt notes: Database Summary (2) SQL model-qsqlquerymodel

The qsqlquerymodel class provides a read-only data model for the SQL result set. Next we will use this class for the simplest operation.

Common functions

Void qsqlquerymodel: setquery ("SQL statement") // executes an SQL statement. You can also input a qsqlquery object. In this case, you can use some features of the qsqlquery class, such as pre-operations.

Setheaderdata () // sets the horizontal header title

Columncount (); // obtain the number of Columns

Columncount (); // obtain the number of Columns

Qsqlrecord qsqlquerymodel: Record (INT row) const // return the information contained in the row to access a single record

Qmodelindex q1_actitemmodel: Index (INT row, int column, const qmodelindex & parent = qmodelindex () // return the index of the specified row and column)

Index. Data () // returns the index value

Query () // return the qsqlquery-related model

QSqlQueryModel *model = new QSqlQueryModel;model->setQuery(“select * from student”);model->setHeaderData(0, Qt::Horizontal, tr(“id”));model->setHeaderData(1, Qt::Horizontal, tr(“name”));QTableView *view = new QTableView;view->setModel(model);view->show();

 

Use query to execute SQL statements

Qsqlquery query = model-> query();query.exe C ("Select name from student where id = 1"); query. next (); qdebug () <query. value (0 ). tostring (); // if the preceding SELECT statement is changed to an insert statement and is displayed in qtableview, You need to query model-> setquery ("select... ") to display the just-inserted statement

Because the qsqlquerymode model is read-only by default, we cannot modify the content in the table in the window. However, we can create our own models, display data and modify data as needed. If you want to make it readable and writable, your class must inherit from qsqlquerymodel and rewrite the setdata () and flags () functions. If you want to change the display of data, you must rewrite data () function.

Qt: itemflags mysqlquerymodel: Flags (const qmodelindex & Index) const // returns the variable flag of the table {QT: itemflags flags = qsqlquerymodel: Flags (INDEX ); if (index. column () = 1) // The second field can be changed, that is, the student Name field flags | = QT: itemiseditable; return flags;} bool mysqlquerymodel :: setdata (const qmodelindex & Index, const qvariant & Value, INT/* role */) // Add data to a table {qmodelindex primarykeyindex = qsqlquerymodel: Index (index. row (), 0); int id = data (primarykeyindex ). toint (); // you can use this method to obtain the ID, primarykeyindex. data (); clear (); bool isok; If (index. column () = 1) // The second attribute can be changed {qsqlquery query; query. prepare ("Update student set name =: name where id =: ID"); query. bindvalue (": Name", "5th"); query. bindvalue (": ID", ID); isok = query.exe C (); refresh (); // You are advised to add the code to refresh the result, or call the refresh function return isok here ;} return false;} void mysqlquerymodel: refresh () // update display {setquery ("select * from student"); setheaderdata (0, QT: horizontal, qobject :: TR ("student ID"); setheaderdata (1, QT: horizontal, qobject: TR ("name "));}//

// Tata () rewrite the display style of a column, alignment qvariant mysqlquerymodel: Data (const qmodelindex & Index, int role) const {qvariant value = qsqlquerymodel :: data (index, role); If (role = QT: textcolorrole & Index. column () = 0) return qvariantfromvalue (qcolor (QT: Red); // The font color of the first attribute is red if (role = QT :: textalignmentrole & Index. column () = 1) {value = (QT: alignvcenter + QT: alignright); // center right vertically} return value ;}