Question

我正在尝试使用Knex使用子查询创建以下查询：

SELECT 
  t.*, 
  (SELECT COUNT(*) FROM team_users tu WHERE TeamID = t.ID) AS UserCount,
  (SELECT COUNT(*) FROM team_access ta WHERE TeamID = t.ID) AS AppCount
FROM teams t WHERE OwnerUserID = _UserID;

结果应该是team表，其中包含来自不同表的UserCount和AppCount的计数聚合（team_users，team_access）

id | Name      | OwnerUserID   | UserCount | AppCount
-----------------------------------------------------
134| Team A    | 1538          | 7         | 6
135| Team B    | 1538          | 4         | 2
136| Team C    | 1538          | 12        | 1

我认为是一个等效的knex实现是：

var subquery1 = Knex.knex('team_users').count('*').where('TeamID', 'teams.ID').as('UserCount');
var subquery2 = Knex.knex('team_access').count('*').where('TeamID', 'teams.ID').as('AppCount');
Knex.knex.select('*', subquery1, subquery2).from('teams').where("OwnerUserID", ownerId).asCallback(dataSetCallback);

运行它，我确实得到了＆＃34; UserCount＆＃34;和＆＃34; AppCount＆＃34;返回对象中的列但始终为零，这可能是因为它没有识别出＆team; ID。在子查询中。

我设法使用Knex.raw函数解决了它：

Knex.knex('teams')
    .select('*', Knex.knex.raw('(SELECT COUNT(*) FROM team_users WHERE TeamID = teams.ID) AS UserCount'), Knex.knex.raw('(SELECT COUNT(*) FROM team_access WHERE TeamID = teams.ID) AS AppCount'))
    .where("OwnerUserID", ownerId)
    .asCallback(dataSetCallback);

但我很想知道如何使用子查询对象来实现这一点。

Answer 1

您正在尝试将teams.ID字符串作为值传递。为了能够.where('columnName', 'otherColumnName')，必须使用knex.ref来传递otherColumnName作为标识符。

var teamsIdColumnIdentifier = knex.ref('teams.ID'); // <-- [1]

var subquery1 = Knex.knex('team_users').count('*')
  .where('TeamID', teamsIdColumnIdentifier).as('UserCount');
var subquery2 = Knex.knex('team_access').count('*')
  .where('TeamID', teamsIdColumnIdentifier).as('AppCount');

Knex.knex.select('*', subquery1, subquery2).from('teams')
  .where("OwnerUserID", ownerId).asCallback(dataSetCallback);

[1]在May 2018中将knex.ref添加到Knex之前，您必须使用knex.raw，就像这样;

var teamsIdColumnIdentifier = knex.raw('??', ['teams.ID']);

使用Knex.js的select语句的子查询

1 个答案: