Knex.js - How To Update a Field With An Expression

问题

How do we get Knex to create the following SQL statement:

UPDATE item SET qtyonhand = qtyonhand + 1 WHERE rowid = 8

We're currently using the following code:

knex('item')
    .transacting(trx)
    .update({qtyonhand: 10})
    .where('rowid', 8)

However, in order for our inventory application to work in a multi-user environment we need the qtyonhand value to add or subtract with what's actually in the database at that moment rather than passing a value that may be stale by the time the update statement is executed.

回答1:

Here are 2 different ways

knex('item').increment('qtyonhand').where('rowid',8)

or

knex('item').update({
  qtyonhand: knex.raw('?? + 1', ['qtyonhand'])
}).where('rowid',8)

来源：https://stackoverflow.com/questions/42212497/knex-js-how-to-update-a-field-with-an-expression