如何在带有 Typescript 的节点中使用 mysql

Question

Background

I'm making a simple website with node and typescript. I installed MySQL module to communicate with a database.

Problem

I'm trying to get data from DB, but I don't know how to determine what type the result should have. For example,

const sql = `SELECT metaValue FROM ${this.table} WHERE metaKey = '${key}'`;
const result = await this.pool.query(sql);
console.log(result);

in this case, the result is [ RowDataPacket { metaValue: 'map-79.jpg' } ] . How can I get map-79.jpg from the result? What type the result should be?

Answer 1

it will return Object Array :

const sql = `SELECT metaValue FROM ${this.table} WHERE metaKey = '${key}'`;
const result = await this.pool.query(sql);
console.log(result);
result.forEach(row => {
    console.log(row.metaValue)
})

Or you Can create array by using map

let imgArray = result.map(row => { return row.metaValue });
console.log(imgArray);

Answer 2

@Pushpendra Kumar was right. But we need type guard before using result as Array like below.

const sql = `SELECT metaValue FROM ${this.table} WHERE metaKey = '${key}'`;
let rows = await this.pool.query(sql);
if ( Array.isArray(rows) ) {
  return rows[0].metaValue
}

Answer 3

I use let records: youDefinedInterface[] = [].slice.call(result, 0); to cast the Query type to a normal array.

Answer 4

@Pushpendra Kumar @Byeongin Yoon watch out for such sql notation,

SELECT metaValue FROM ${this.table} WHERE metaKey = '${key}' should be

SELECT metaValue FROM ? WHERE metaKey = ? and then pass params as arrays.

Sanitise your queries guys.