How to use mysql in node with Typescript

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?

Pushpendra Kumar · Accepted Answer · 2019-06-04 12:04:44Z

2

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);

answered Jun 4, 2019 at 12:04

Pushpendra Kumar

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1 Comment

Byeongin Yoon Over a year ago

It returns Query type. I cannot use foreach or map because it is not Array type.

Byeongin Yoon · Accepted Answer · 2019-06-04 12:39:54Z

0

@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
}

answered Jun 4, 2019 at 12:39

Byeongin Yoon

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Comments

Wayne Li · Accepted Answer · 2019-11-02 07:13:25Z

0

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

answered Nov 2, 2019 at 7:13

Wayne Li

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