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ViewsCan someone clarify what is happening in this part of the code?
So I have part of code like this
ruter.get('/', async function (_, res) {
const [categories, items] = (await Promise.all([
db.query('SELECT * FROM categories'),
db.query('SELECT * FROM inventory'),
])).map(result => result.rows);
for (const category of categories) {
category.items = items.filter(item => (item.categoryid === category.id));
}
I have database where I have table-categories and table-items categories table and items look like this:
What I don't understand is what happens with categories and inventory in this part of code ->
db.query('SELECT * FROM categories'),
db.query('SELECT * FROM inventory'),
])).map(result => result.rows);
Do they get joined? Also in this part
category.items = items.filter(item => (item.categoryid === category.id));
what item means here, there is no column named item in items table?
thank you!
·
Juan Pablo Isaza
1 answers
Answer question0
This
const [categories, items] = (await Promise.all([
db.query('SELECT * FROM categories'),
db.query('SELECT * FROM inventory'),
])).map(result => result.rows);
- makes two queries - one from categories, one from inventory
- in parallel, with
Promise.all - then takes the
rowsproperty from each query result and puts those into thecategoriesanditemsvariables.
They don't get joined - they're two entirely independent queries and get put into separate categories and items variables.
what item means here
With
items.filter(item =>
items is the result of the query SELECT * FROM inventory - item is a single row from that query.
·
Juan Pablo Isaza
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