单击搜索按钮时,它会像这样显示表中的第一条记录;
void EditEntry::on_search_button_clicked() {
QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");
db.setDatabaseName("database.db");
bool ok = db.open();
if (ok) {
QSqlQuery query1("SELECT * FROM table_name WHERE last_name LIKE '%Nana%'");
if (query1.first()) {
//show first record in the table where last name like Nana
}
}
我正在尝试通过单击这样的按钮使查询移动到表中的下一条记录;
void EditEntry::on_next_button_clicked() {
QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");
db.setDatabaseName("database.db");
bool ok = db.open();
if (ok) {
QSqlQuery query1("SELECT * FROM table_name WHERE last_name LIKE '%Nana%'");
if (query1.isActive()) {
while (query1.next()) {
//show the next record in the table with last name like Nana
}
}
并像这样显示名称为"娜娜"的上一张记录;
void EditEntry::on_previous_button_clicked() {
QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");
db.setDatabaseName("database.db");
bool ok = db.open();
if (ok) {
QSqlQuery query1("SELECT * FROM table_name WHERE last_name LIKE '%Nana%'");
if (query1.isActive()) {
while (query1.previous()) {
//show previous record in the table where last name like Nana
}
}
该on_search_button_clicked()
通过显示姓氏(如"娜娜")的第一条记录来很好地工作。on_next_button_clicked()
显示表中名称为"Nana"的最后一条记录,而不是第 1 条之后的下一条记录(表中有 3 条姓氏为"Nana"的记录)。on_previous_button_clicked()
按钮根本不起作用,即使我希望它显示姓氏(如"娜娜")的上一条记录,它也不会显示任何内容。如何让这些按钮按预期工作?
附言:我想要的是,每当单击on_next_button_clicked()
时,它应该继续显示下一条记录,直到到达表中的最后一条记录。
next()
只能处理QSqlQuery
的一个实例,但在on_search_button_clicked()
结束时,on_next_button_clicked()
和on_previous_button_clicked()
丢弃QSqlQuery
的实例(以及QSqlDatabase
)。
我认为您可以将偏移变量int offset_ = 0
存储在EditEntry
类中,然后执行类似操作
void EditEntry::on_next_button_clicked() {
offset_ += 1;
QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");
db.setDatabaseName("database.db");
bool ok = db.open();
if (ok) {
QString sql = QString("SELECT * FROM table_name WHERE last_name LIKE '%Nana%' LIMIT ") + QString::number(offset_) + QString(", 1");
QSqlQuery query1(sql);
if (query1.isActive()) {
while (query1.first()) {
//show the next record in the table with last name like Nana
}
}
}
}
另一个:
void EditEntry::on_previous_button_clicked() {
offset_ -= 1;
QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");
db.setDatabaseName("database.db");
bool ok = db.open();
if (ok) {
QString sql = QString("SELECT * FROM table_name WHERE last_name LIKE '%Nana%' LIMIT ") + QString::number(offset_) + QString(", 1");
QSqlQuery query1(sql);
if (query1.isActive()) {
while (query1.first()) {
//show the next record in the table with last name like Nana
}
}
}
}