Knex: 从选择查询返回单个值的正确方法是什么？

db('table_name').where({id: 1}).first().then((row) => row)

应该管用

哦，实际上是first ，我一直在寻找one ， selectOne等。谢谢

db（'table_name'）。where（{id：1}）。first（）; 这将相同。 没有？

@ arch-mage如果仅应有一个匹配结果，则确保它是最佳实践，常见的single实现使用limit 2 。 这是将其添加到Knex的方法。

import Knex from 'knex'

declare module 'knex' {
  interface QueryInterface {
    _method: string
    _isSelectQuery: () => boolean
    single: (columns?: string | string[], notFoundMessage?: string, notSingleMessage?: string) => Promise<any>
  }
}

Knex.QueryBuilder.extend('single', function single(
  this: Knex.QueryBuilder,
  columns: string | string[] = '*',
  notFoundMessage?: string,
  notSingleMessage?: string,
): any {
  // eslint-disable-next-line no-underscore-dangle
  if (!this._isSelectQuery() || this._method === 'first')
    // eslint-disable-next-line no-underscore-dangle
    throw new Error(`Cannot chain .single() on "${this._method}" query!`)
  // eslint-disable-next-line no-param-reassign
  if (typeof columns === 'string') columns = [columns]
  const allColumns = columns.includes('*')
  const singleColumn = !allColumns && columns.length === 1 ? columns[0] : false
  if (!allColumns) this.select(...columns)
  this.limit(2)
  return this.then((results: any[]) =>
    results.length === 1
      ? singleColumn
        ? results[0][singleColumn]
        : results[0]
      : results.length
      ? Promise.reject(notSingleMessage || `Query has more than one result: "${this.toSQL().sql}"`)
      : Promise.reject(notFoundMessage || `Query has no results: "${this.toSQL().sql}"`),
  )
} as any)

@wubzz您对PR添加single方法到QueryInterface中的PR感兴趣吗？