Union

union api combine the result of two or more select query and remove duplicate records.

Use Case

There are times when one query is not able to fulfill the situation and so you need to use multiple query but now you are in a situation where some of the values are same in both results. union api is useful in these situation where it combines the results of multiple select query and removes the duplicate records.

e.g - Consider below queries -

1st query

connection.select({
    from: 'Products',
    where: {
        price: {
            '>': 10
        }
    }
})

2nd query

connection.select({
    from: 'Products',
    where: {
        price: {
            '>': 50
        }
    }
})

now in the above two queries - results from first query will have some records existing in results of 2nd query.

so using union we will combine these two results and query will be -

var results = await connection.union([
    {
        from: 'Products',
        where: {
            price: {
                '>': 10
            }
        }
    },
    {
        from: 'Products',
        where: {
            price: {
                '>': 50
            }
        }
    }
])

Example