Take only one value in the query result to the database

Question

I’d like him to pass one return with only the number of data of that table, however it is returning it:

C:\E. S>node dao.js
Connected!
[ RowDataPacket { 'COUNT(*)': 4 } ]

Code:

contaQuantidade(tabela){
        var conector = this.conectaBanco();
        conector.connect(function(err) {
            if (err) throw err;
            console.log("Connected!");          
            conector.query("select COUNT(*) from "+tabela, function (err, result) {
                if (err) throw err;
                var i = result;
            });
            conector.end();
        });
        return i;
    }

How do I pick only the number 4?

Answer 1

You can use the AS to create an alias for COUNT(*), to make it easier to access in Javascript. So your query will look like this:

SELECT COUNT(*) AS count FROM nome_da_tabela;

The result will come like this:

+-------+
| count |
+-------+
|     4 |
+-------+

Then, to access the value, we need to access the first item of RowDataPacket returned. For this, we will use the following notation:

// Acessa o primeiro elemento dos resultados:
//    ↓↓↓
result[0]

And to access the number returned, just access the property count, as we define as alias in our query.

result[0].count

The code goes something like this:

connection.query('SELECT COUNT(*) AS count FROM ' + table + ';', (err, result) => {
  if (err) throw err

  // ℹ️ Acessamos o número de tabela na linha abaixo:
  const number = result[0].count

  console.log('Temos ' + number + ' registros na tabela ' + table + '.')
})