GoFrame ORM 组件支持 Union/UnionAll 操作， Union/UnionAll 操作符用于连接两个以上的 SELECT 语句的结果组合到一个结果集合中，关于 Union/UnionAll 组合查询的相关介绍可以参考MySQL的官方文档介绍 https://dev.mysql.com/doc/refman/8.0/en/union.html 。我们可以通过链式操作或者方法操作来实现 Union/UnionAll 操作。

方法定义

  1. // Union does "(SELECT xxx FROM xxx) UNION (SELECT xxx FROM xxx) ..." statement.
  2. func (c *Core) Union(unions ...*Model) *Model
  4. // UnionAll does "(SELECT xxx FROM xxx) UNION ALL (SELECT xxx FROM xxx) ..." statement.
  5. func (c *Core) UnionAll(unions ...*Model) *Model

Union

使用 Union 操作符，多个 SELECT 语句会删除重复的数据。

  1. // 获取默认配置的数据库对象(配置名称为"default")
  2. db := g.DB()
  4. db.Union(
  5.     db.Model("user").Where("id", 1),
  6.     db.Model("user").Where("id", 2),
  7.     db.Model("user").WhereIn("id", g.Slice{1, 2, 3}),
  8. ).OrderDesc("id").All()
  9. // (SELECT * FROM `user` WHERE `id`=1)
  10. // UNION
  11. // (SELECT * FROM `user` WHERE `id`=2)
  12. // UNION
  13. // (SELECT * FROM `user` WHERE `id` IN (1,2,3)
  14. // ORDER BY `id` DESC) ORDER BY `id` DESC

也可以通过 dao 链式操作实现：

  1. dao.User.Union(
  2.     dao.User.Where(dao.User.Columns.Id, 1),
  3.     dao.User.Where(dao.User.Columns.Id, 2),
  4.     dao.User.WhereIn(dao.User.Columns.Id, g.Slice{1, 2, 3}),
  5. ).OrderDesc(dao.User.Columns.Id).All()
  6. // (SELECT * FROM `user` WHERE `id`=1)
  7. // UNION
  8. // (SELECT * FROM `user` WHERE `id`=2)
  9. // UNION
  10. // (SELECT * FROM `user` WHERE `id` IN (1,2,3)
  11. // ORDER BY `id` DESC) ORDER BY `id` DESC

UnionAll

使用 UnionAll 操作符，多个 SELECT 语句不会删除重复的数据。

  1. db.UnionAll(
  2.     db.Model("user").Where("id", 1),
  3.     db.Model("user").Where("id", 2),
  4.     db.Model(table).WhereIn("id", g.Slice{1, 2, 3}),
  5. ).OrderDesc("id").All()
  6. // (SELECT * FROM `user` WHERE `id`=1)
  7. // UNION ALL
  8. // (SELECT * FROM `user` WHERE `id`=2)
  9. // UNION ALL
  10. // (SELECT * FROM `user` WHERE `id` IN (1,2,3)
  11. // ORDER BY `id` DESC) ORDER BY `id` DESC

也可以通过 dao 链式操作实现：

  1. dao.User.UnionAll(
  2.     dao.User.Where(dao.User.Columns.Id, 1),
  3.     dao.User.Where(dao.User.Columns.Id, 2),
  4.     dao.User.WhereIn(dao.User.Columns.Id, g.Slice{1, 2, 3}),
  5. ).OrderDesc(dao.User.Columns.Id).All()
  6. // (SELECT * FROM `user` WHERE `id`=1)
  7. // UNION ALL
  8. // (SELECT * FROM `user` WHERE `id`=2)
  9. // UNION ALL
  10. // (SELECT * FROM `user` WHERE `id` IN (1,2,3)
  11. // ORDER BY `id` DESC) ORDER BY `id` DESC