Configuration 

Exports are configured in page TSconfig below mod.web_xlsexport. Every direct sub-key is one export offered by the backend module; the key is also used to reference the export internally:

mod.web_xlsexport {
    # "orders" is the export key
    orders {
        label = Orders of this page
        table = tx_myext_order
        select {
            10 = uid
            20 = order_number
        }
        fieldLabels {
            10 = ID
            20 = Order number
        }
    }
}

Each definition is translated one-to-one into a TYPO3 QueryBuilder query: values are bound with QueryBuilder::createNamedParameter() and column names are quoted with QueryBuilder::quoteIdentifier().