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Qt SQL example 1 is a
Qt SQL example.
Technical facts
Operating system(s) or programming environment(s)
IDE(s):
Project type:
C++ standard:
Compiler(s):
Libraries used:
STL: GNU ISO C++ Library, version 4.9.2
Qt project file: ./CppQtSqlExample1/CppQtSqlExample1.pro
./CppQtSqlExample1/main.cpp
#include <cassert>
#include <iostream>
#include <QtSql>
int main()
{
//Create a database
QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE"); //Choose from QSQLITE QODBC3 QODBC
db.setDatabaseName("MY_DATABASE");
const bool ok = db.open();
assert(ok);
//Delete the table 'PEOPLE' from a possible previous session
QSqlQuery("DROP TABLE PEOPLE");
assert(db.tables().empty() && "There must be zero tables at startup");
//Creata a 'PEOPLE' table
QSqlQuery("CREATE TABLE PEOPLE (ID INT PRIMARY KEY NOT NULL, NAME TEXT NOT NULL)");
assert(db.tables().size() == 1 && "Table PEOPLE must have been created");
//Check that table is empty
{
QSqlQuery query("SELECT * FROM PEOPLE");
//Using QSqlQuery::size is not supported by all drivers, so count the number of rows manually
int size = 0;
while (query.next()) { ++size; }
assert(size == 0 && "Table PEOPLE must be empty directly after its creation");
}
//Insert people
QSqlQuery("INSERT INTO PEOPLE VALUES (1,\"Mr. A\")");
QSqlQuery("INSERT INTO PEOPLE VALUES (2,\"Ms. B\")");
QSqlQuery("INSERT INTO PEOPLE VALUES (3,\"Mr. C\")");
//Check that table is not empty anymore
{
QSqlQuery query("SELECT * FROM PEOPLE");
//Using QSqlQuery::size is not supported by all drivers, so count the number of rows manually
int size = 0;
while (query.next()) { ++size; }
assert(size == 3 && "Table PEOPLE must contain three persons");
}
//Display content of PEOPLE on screen
{
QSqlQuery query("SELECT * FROM PEOPLE");
std::cout << "#\tID\tNAME\n";
int index = 0;
while (query.next())
{
const int id = query.value(0).toInt();
const std::string name = query.value(1).toString().toStdString();
std::cout << index << '\t' << id << '\t' << name << '\n';
++index;
}
}
}
/* Screen output:
# ID NAME
0 1 Mr. A
1 2 Ms. B
2 3 Mr. C
*/
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