无法使用 Node.JS 将 null 的值发送到 MySQL 数据库

Question

I'm trying to send null to my MySQL database using Node.JS:

con.query("INSERT INTO Routes (routeTrigger) VALUES ( " + null + " )", {title: 'test'}, function(err, result) {
    if (err) throw err;
});

But when looking in the database, the updated value reads 'null' . The database's NULL is supposed to read NULL . If I send capital NULL instead, that doesn't even work (in Node.JS). If I send 'NULL' it sends the string "NULL", and not the database's NULL .

Answer 1

JavaScript's null is not the same as SQL's Null . You want (in your case, using raw SQL strings) a string:

con.query("INSERT INTO Routes (routeTrigger) VALUES ( null )", {title: 'test'}, function(err, result) {
    if (err) throw err;
});

But note that that creates a row that's entirely null . Which is possible, but it's unlikely what you want.

What are you actually trying to do?

Answer 2

If you want to assign the NULL value In the SQL tables, you can think differently.

Instead of assigning NULL , you can tweak the field (column) so that the default value (when no value is assigned) is : NULL .

Now, when you insert your new row, just don't assign any value to that field .

---

Example :

Let's say the table is structured like so :

MyTable

id : auto increment; ...

name : text

url : text; default = NULL

Then you could do:

INSERT INTO Mytable ( name ) VALUES ( "Joe" );

As you omit the url information, it gets set to NULL .

Answer 3

To pass null value in mysql using nodejs, we need a different kind of implementation of a query.

conn.query({
    sql: `INSERT INTO project values(?, ?, ?, ?);`,
    values: [projectId, name, startDate, endDate]}, (error, results) => {
        if (error) {
            console.log("Error executing sql: ", error.message);
            return res.send(error);
        }
    });
});

Official site says: "undefined / null are converted to NULL" and it works.

Use that above syntax to fire a query.

Answer 4

This was used for PostgresQL table migration from JSON using Node.js; may help. Check the values coming from your source, and if it doesn't exist for that column, use "NULL" with double quotes. EG, if it's JSON:

const makeVal = (val) => {
    if (val === undefined) {
        return "NULL"
    } else {
        return "'" + JSON.stringify(val).replace(/'/g, "''") + "'" 
    }
}

See this gist https://gist.github.com/foureyedraven/ca90a7dcbfd0918c153b0c91ec9317c5 for full implementation.

Answer 5

Using the Node mysql package I was able to insert a null value by doing the following:

let myValue = null;

Note the column configuration:

'myValue' varchar(15) DEFAULT NULL

Answer 6

it worked

if (my_var != null) {
    my_var = '"' + my_var + '"';
}                             
else {
    my_var = "NULL";
}
connection.query('insert into my_table(my_var) values(' + my_var + ')', (error, results) => {
    if (error) {
        throw error;
    }
    connection.end();
});