Deleting row from MySQL database

[veera]

Hi All,
I am fetching the existing table from the mssql server using qtcreator now i want to delete data of specific row such as ID i am using this api query->prepare("DELETE FROM entry where id = 'id' "); can any one tell me why it is not deleting specific row......

---

forked from here to new thread. please do not resurrect 10 months old threads with not really related questions ~ VRonin

[VRonin]

this: query->prepare("DELETE FROM entry where id = 'id' "); does not even compile

What you want to achieve is explained in the docs: http://doc.qt.io/qt-5/qsqlquery.html#approaches-to-binding-values (they use INSERT instead of DELETE but it's exacly the same mechanic)

[veera]

Hi VRonin,
It was successfully compiled and if i pass ID number it will be deleting entire row using push button i want it in a generic way instead of hardcoding......

[J.Hilk]

@veera
I still don't get your question, entirely,

did you read the link @VRonin gave you?

queryDelete.prepare("DELETE FROM entry where id = ':id' ");
queryDelete.bindValue(":id",value);

[veera]

Hi
I am inserting a integer number using qlineedit like this
"int contact_no = ui->lineEdit_3->text().toInt();
query->addBindValue(contact_no);" now my problem is it is accepting only 9 digit numbers only not more than that 10 ,11,etc .please tell which data type i need to use if want give more than 9 digits number ......

[VRonin]

what type is id in your database?

[veera]

int type

[jsulm]

@veera Can you show the CREATE TABLE query you're using for the table where you're trying to insert int > 9digits?

[veera]

@VRonin said in Deleting row from MySQL database:

what type is id in your database?

int type only......

[VRonin]

int in MySQL goes from -2147483648 to 2147483647 (or from 0 to 4294967295 if unsigned) (ref: https://dev.mysql.com/doc/refman/5.7/en/integer-types.html) and same goes for a c++ int variable in most environments so it's only natural you can't use the majority of numbers with 10 digits.

Use a BIGINT (qint64 in C++) to go to 18 digits or just use a string

[veera]

@jsulm
Here is my table
CREATE TABLE entry (id INT,name NVARCHAR(200),contact_no INT,lastname NVARCHAR(200),emailid NVARCHAR(200));

[jsulm]

@veera See explanation from @VRonin

[veera]

@VRonin
I am using MSSQL on ubuntu 16.04 LTS 64 bit
after using qint64 instead of int in qtcreator application..... also samething is coming i.e 0 if i am inserting more than 10 digits....

[jsulm]

@veera You need to change the data type of id in your database (BIGINT as @VRonin already said) , not just use qint64 in your code.
Why do you need such big numbers?

[veera]

i want to store the mobile No is 10 digits so after declaring qint64 also same issue is coming ....

[mrjj]

@veera
Hi
int contact_no = ui->lineEdit_3->text().toInt();

This is still int and limit in range

So you are looking at something like

bool ok;
QString input=ui->lineEdit_3->text();// take text
qint64 contact_no = input.toLongLong(&ok); // convert
if (!ok) {
error("invalid value");
return;
}
..
Convert was ok, use.