在 Knex.js 中派生别名 table

Question

我正在使用 Knex，我想将此原始查询转换为 Knex 语法：

SELECT
    t.id,
    t.objectId,
    t.objectType
FROM (
         SELECT
                tableA.tableC_Id AS Id,
                tableA.id AS objectId,
                'TypeA' AS objectType
         FROM tableA
         UNION
         SELECT
                tableB.tableC_Id AS Id,
                tableB.id AS objectId,
                'TypeB' AS objectType
         FROM tableB
     ) t
INNER JOIN tableC ON tableC.id = t.Id

我没有内部连接的尝试：

const qb = di
        .get(DatabaseConnection)
        .queryBuilder()
        .select('*')
        .from(() => {
            tableA
                .queryBuilder()
                .select([
                    { id: tableA.col('Id') },
                    { objectId: tableA.col('id') },
                    { objectType: connection.raw('\'TypeA\'') },
                ])
                .union([
                    tableB
                        .queryBuilder()
                        .select([
                            { id: tableB.col('Id') },
                            { objectId: tableB.col('id') },
                            { objectType: tableB.raw('\'TypeB\'') },
                        ])
                ])
                .as('t');
        });

但是 Knex 将其转换为

SELECT * FROM (SELECT * )

。我不喜欢使用原始 SQL-查询，这可能吗？

Answer 1

knex(
  knex('tableA').select(
      'tableA.tableC_Id as Id', 
      'tableA.id as objectId', 
      knex.raw("? as objectType", ['TypeA'])
    )
    .union([
      knex('tableB').select(
        'tableB.tableC_Id as Id', 
        'tableB.id as objectId', 
        knex.raw("? as objectType", ['TypeB'])
      )
    ])
    .as('t')
)
.select('t.id', 't.objectId', 't.objectType')
.join('tableC', 'tableC.id', 't.Id')

输出：

select "t"."id", "t"."objectId", "t"."objectType" 
from (
  select "tableA"."tableC_Id" as "Id", "tableA"."id" as "objectId", ? as objectType 
  from "tableA" 
  union select "tableB"."tableC_Id" as "Id", "tableB"."id" as "objectId", ? as objectType 
  from "tableB"
) as "t" inner join "tableC" on "tableC"."id" = "t"."Id"

https://runkit.com/embed/emqvxez8mupo

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