Why is my dynamic sql resulting in the error shown below? - postgresql

Question

I am trying to build a sql statement dynamically and this is one variation of the result.
sqlQuery {
name: 'fetch-products',
text: 'select * from products where category =
$1 and designer in $2',
values: [ 'WOMENSCLOTHING', "('Adjavon', 'ALC', 'Adele', 'Bagley')" ]
}
I build the sql with the following code segment:
const {
category,
designers,
} = JSON.parse(filters);
let values = [category];
let text = 'select * from products where category = $1';
if(designers) {
text = text + ' and designer in $2';
values.push(designers);
}
I execute it in the following segment:
try {
const allProducts = await pool.query(sqlQuery);
res.status(200).json(allProducts.rows);
} catch (error) {
console.error(error);
return res.status(500).send('Problems gettting products by category.')
}
And get the following error:
error: syntax error at or near "$2"
I am thinking the error may be the double quotes placed around designer when it is pushed on the values array:
values: [ 'WOMENSCLOTHING', "('Adjavon', 'ALC', 'Adele', 'Bagley')" ]

Answer 1

I don't know what library you are using exactly, but the values property looks highly suspicious.
sqlQuery {
name: 'fetch-products',
text: 'select * from products where category =
$1 and designer in $2',
values: [ 'WOMENSCLOTHING', "('Adjavon', 'ALC', 'Adele', 'Bagley')" ]
}
If your drivr/library supports this, the second element in the array should be an actual array and not a string like '("foo", "bat")'. How is the driver supposed to know this is meant as a list and not a single string that has this value?
I guess in a nutshell you have to bring the query in this form:
const query = 'select * from products where category = $1 and designer in ($2, $3, $4, $5)'
const values = [ 'WOMENSCLOTHING', 'Adjavon', 'ALC', 'Adele', 'Bagley' ]
That requires some extra work on the backend to map the values and bring them into the right shape.
I guess you could get that done with something like this:
const category = 'icecream'
const designers = ['jim', 'maria']
let values = [category];
let text = 'select * from products where category = $1';
if (designers) {
text += ` and designer in (${designers.map((d, i) => `$${i+2}`).join(', ')})`;
values = [...values, ...designers];
}
console.log(text);
console.log(values);