GoFrame 数据查询-Union/UnionAll
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
// Union does "(SELECT xxx FROM xxx) UNION (SELECT xxx FROM xxx) ..." statement.
func (c *Core) Union(unions ...*Model) *Model
// UnionAll does "(SELECT xxx FROM xxx) UNION ALL (SELECT xxx FROM xxx) ..." statement.
func (c *Core) UnionAll(unions ...*Model) *ModelUnion
使用Union操作符，多个SELECT语句会删除重复的数据。
// 获取默认配置的数据库对象(配置名称为"default")
db := g.DB()
db.Union(
db.Model("user").Where("id", 1),
db.Model("user").Where("id", 2),
db.Model("user").WhereIn("id", g.Slice{1, 2, 3}),
).OrderDesc("id").All()
// (SELECT * FROM `user` WHERE `id`=1)
// UNION
// (SELECT * FROM `user` WHERE `id`=2)
// UNION
// (SELECT * FROM `user` WHERE `id` IN (1,2,3)
// ORDER BY `id` DESC) ORDER BY `id` DESC 也可以通过dao链式操作实现：
dao.User.Union(
dao.User.Where(dao.User.Columns.Id, 1),
dao.User.Where(dao.User.Columns.Id, 2),
dao.User.WhereIn(dao.User.Columns.Id, g.Slice{1, 2, 3}),
).OrderDesc(dao.User.Columns.Id).All()
// (SELECT * FROM `user` WHERE `id`=1)
// UNION
// (SELECT * FROM `user` WHERE `id`=2)
// UNION
// (SELECT * FROM `user` WHERE `id` IN (1,2,3)
// 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。
db.UnionAll(
db.Model("user").Where("id", 1),
db.Model("user").Where("id", 2),
db.Model(table).WhereIn("id", g.Slice{1, 2, 3}),
).OrderDesc("id").All()
// (SELECT * FROM `user` WHERE `id`=1)
// UNION ALL
// (SELECT * FROM `user` WHERE `id`=2)
// UNION ALL
// (SELECT * FROM `user` WHERE `id` IN (1,2,3)
// ORDER BY `id` DESC) ORDER BY `id` DESC 也可以通过dao链式操作实现：
dao.User.UnionAll(
dao.User.Where(dao.User.Columns.Id, 1),
dao.User.Where(dao.User.Columns.Id, 2),
dao.User.WhereIn(dao.User.Columns.Id, g.Slice{1, 2, 3}),
).OrderDesc(dao.User.Columns.Id).All()
// (SELECT * FROM `user` WHERE `id`=1)
// UNION ALL
// (SELECT * FROM `user` WHERE `id`=2)
// UNION ALL
// (SELECT * FROM `user` WHERE `id` IN (1,2,3)
// ORDER BY `id` DESC) ORDER BY `id` DESC