Java code not compiling with a SQL statement

Question

I am trying to delete a record from a database using the following code in Java

try {
    Statement st = db.con.createStatement();
    con.stmt = st.executeUpdate("DELETE FROM item, WHERE Name=" + textField_name.getText());

however "stmt", (which is my PreparedStatement initialized in my connection class), is underlined and the code doesn't compile.

Jon Skeet · Accepted Answer · 2012-03-08 17:59:11Z

4

That's because executeUpdate returns an int, and presumably con.stmt isn't an int variable.

You shouldn't write your SQL that way in the first place though (it's invalid anyway due to the comma after item) - you should use a prepared statement:

PreparedStatement st = db.con.prepareStatement("DELETE FROM item WHERE Name=?");
st.setString(1, textField_name.getText());
int rowsDeleted = st.executeUpdate();

That way you don't open yourself up to SQL injection attacks.

answered Mar 8, 2012 at 17:59

Jon Skeet

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9 Comments

FatmaTurk Over a year ago

Like I said I have initialized my PreparedStatement in my connection class... I don't really understand what the second line is doing do you mind just explaining please as I am new to java.

Jon Skeet Over a year ago

@FatmaTurk: That's not the way prepared statements work though. You prepare the statement with the SQL, then set the parameters. It's not clear how you've prepared the statement before the code you've shown us, but the code you've shown definitely won't work, whereas the code I've shown should.

FatmaTurk Over a year ago

I am still getting the following error [java.sql.SQLException: Parameter index out of range (1 > number of parameters, which is 0)]

Churk Over a year ago

@Jon Skeet, he is using a Statement and not a PreparedStatement class, so therefore, his st.executeUpdate(......) would work, BAD practice, but it works, it's basically executing a regular SQL statement. But the comma after item is an issue, but that would not cause a compiler error, more of a runtime error.

Jon Skeet Over a year ago

@Churk: No, it wouldn't work - because (as I said in the very first sentence) he's trying to assign the result to con.stmt. That's what's causing the compiler error.

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Christian Kuetbach · Accepted Answer · 2012-03-08 17:58:35Z

1

st.executeUpdate() returns an int.

I think you wanted to execute con.stmt.executeUpdate()

answered Mar 8, 2012 at 17:58

Christian Kuetbach

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1 Comment

FatmaTurk Over a year ago

now I understand why it was asking me to change "stmt" to "int"

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