Update Table
You can update existing records in a table by using the "UPDATE" statement:
Example
Overwrite the address column from "Valley 345" to "Canyon 123":
let mysql = require('mysql');
let con = mysql.createConnection({
host: "localhost", user: "yourusername",
password: "yourpassword", database: "mydb"
});
con.connect(function(err) {
if (err) throw err;
let sql = "UPDATE customers SET address = 'Canyon 123' WHERE address = 'Valley 345'";
con.query( sql, function (err, result) {
if (err) throw err;
console.log(result.affectedRows + " record(s) updated");
});
});Notice the WHERE clause in the UPDATE syntax: The WHERE clause specifies which record or records that should be updated. If you omit the WHERE clause, all records will be updated!
Save the code above in a file called "demo_db_update.js" and run the file:
Run "demo_db_update.js"
C:\Users\
Your Name
>node demo_db_update.jsWhich will give you this result
1 record(s) updatedThe Result Object
When executing a query, a result object is returned.
The result object contains information about how the query affected the table.
The result object returned from the example above looks like this:
{
fieldCount: 0, affectedRows: 1, insertId: 0,
serverStatus: 34, warningCount: 0, message: '(Rows matched: 1 Changed: 1 Warnings: 0', protocol41: true,
changedRows: 1
}The values of the properties can be displayed like this:
Return the number of affected rows
console.log(result.affectedRows)Which will produce this result
1