使用字段别名作为 javascript 对象的键

Question

How do I use a field alias as the key of a javascript object?

const countries = {
    'united states of america': 'US',
    'india': 'IN',
    'china': 'CN'
}
const query = `SELECT country AS ctry, IF(true, '${countries[ctry]}', 'p') AS c FROM ${table}`

This obviously returns ctry is not defined error as ctry is considered a javascript variable. Is there a way to make this query return values of keys in the countries object when the key is retrieved from database?

Answer 1

SQL CASE

And this done:

 const countries = { 'united states of america': 'US', 'india': 'IN', 'china': 'CN' } const query = `SELECT country AS ctry, CASE WHEN ctry='united states of america' THEN 'US' as c WHEN ctry='india' THEN 'IN' as c WHEN ctry='china' THEN 'CN' as c ELSE 'no country find' as c END FROM ${table}`

Answer 2

To do this in json object you need to use a for:

 const countries = { 'united states of america': 'US', 'india': 'IN', 'china': 'CN' } const query = `SELECT country AS ctry FROM ${table}` //Execute here your request let c = []; for (let i = 0; i < query.length; i ++) { c.push(query[i]['country']) } for (let j = 0; j < c.length; j ++) { c[j] = countrie[c[j]] } console.log(c)

I can't do more with your information.

Answer 3

Convert your countries object into an array using Object.entries then .map them to output WHEN '${i[0]}' THEN '${i[1]}' . This will give you the WHEN parts for each country. Just append this string into your query ( CASE country \\n${caseStr}\\nEND ) then you'll have the full CASE Statement built for you.

 const table = 'test'; const countries = { 'united states of america': 'US', 'india': 'IN', 'china': 'CN' }; const caseStr = Object.entries(countries).map(i => `WHEN '${i[0]}' THEN '${i[1]}'`).join('\\n'); const query = `SELECT country AS ctry \\n, CASE country \\n${caseStr}\\nEND AS c FROM ${table}` console.log(query);

Why store it in JSON though? It looks like you can access the DB anyway, why not store the countries in a table to which you can JOIN your query to?