FreeSql/FreeSql/Interface/Curd/ISelect/ISelectGrouping.cs

using System;
using System.Collections.Generic;
using System.Linq.Expressions;
using System.Text;
using System.Threading.Tasks;

namespace FreeSql {
	public interface ISelectGrouping<TKey, TValue> {
		/// <summary>
		/// 按聚合条件过滤，Where(a => a.Count() > 10)
		/// </summary>
		/// <param name="exp">lambda表达式</param>
		/// <returns></returns>
		ISelectGrouping<TKey, TValue> Having(Expression<Func<ISelectGroupingAggregate<TKey, TValue>, bool>> exp);

		/// <summary>
		/// 按列排序，OrderBy(a => a.Time)
		/// </summary>
		/// <typeparam name="TMember"></typeparam>
		/// <param name="column"></param>
		/// <returns></returns>
		ISelectGrouping<TKey, TValue> OrderBy<TMember>(Expression<Func<ISelectGroupingAggregate<TKey, TValue>, TMember>> column);
		/// <summary>
		/// 按列倒向排序，OrderByDescending(a => a.Time)
		/// </summary>
		/// <param name="column">列</param>
		/// <returns></returns>
		ISelectGrouping<TKey, TValue> OrderByDescending<TMember>(Expression<Func<ISelectGroupingAggregate<TKey, TValue>, TMember>> column);

		/// <summary>
		/// 执行SQL查询，返回指定字段的记录，记录不存在时返回 Count 为 0 的列表
		/// </summary>
		/// <typeparam name="TReturn">返回类型</typeparam>
		/// <param name="select">选择列</param>
		/// <returns></returns>
		List<TReturn> ToList<TReturn>(Expression<Func<ISelectGroupingAggregate<TKey, TValue>, TReturn>> select);
		Task<List<TReturn>> ToListAsync<TReturn>(Expression<Func<ISelectGroupingAggregate<TKey, TValue>, TReturn>> select);

		/// <summary>
		/// 【linq to sql】专用方法，不建议直接使用
		/// </summary>
		List<TReturn> Select<TReturn>(Expression<Func<ISelectGroupingAggregate<TKey, TValue>, TReturn>> select);

		/// <summary>
		/// 返回即将执行的SQL语句
		/// </summary>
		/// <typeparam name="TReturn">返回类型</typeparam>
		/// <param name="select">选择列</param>
		/// <returns></returns>
		string ToSql<TReturn>(Expression<Func<ISelectGroupingAggregate<TKey, TValue>, TReturn>> select);


		/// <summary>
		/// 查询向后偏移行数
		/// </summary>
		/// <param name="offset"></param>
		/// <returns></returns>
		ISelectGrouping<TKey, TValue> Skip(int offset);
		/// <summary>
		/// 查询向后偏移行数
		/// </summary>
		/// <param name="offset">行数</param>
		/// <returns></returns>
		ISelectGrouping<TKey, TValue> Offset(int offset);
		/// <summary>
		/// 查询多少条数据
		/// </summary>
		/// <param name="limit"></param>
		/// <returns></returns>
		ISelectGrouping<TKey, TValue> Limit(int limit);
		/// <summary>
		/// 查询多少条数据
		/// </summary>
		/// <param name="limit"></param>
		/// <returns></returns>
		ISelectGrouping<TKey, TValue> Take(int limit);

		/// <summary>
		/// 分页
		/// </summary>
		/// <param name="pageNumber">第几页</param>
		/// <param name="pageSize">每页多少</param>
		/// <returns></returns>
		ISelectGrouping<TKey, TValue> Page(int pageNumber, int pageSize);
	}

	public interface ISelectGroupingAggregate<TKey> {
		/// <summary>
		/// 分组的数据
		/// </summary>
		TKey Key { get; set; }
		/// <summary>
		/// 记录总数
		/// </summary>
		/// <returns></returns>
		int Count();
		/// <summary>
		/// 求和
		/// </summary>
		/// <typeparam name="T3"></typeparam>
		/// <param name="column"></param>
		/// <returns></returns>
		T3 Sum<T3>(T3 column);
		/// <summary>
		/// 平均值
		/// </summary>
		/// <typeparam name="T3"></typeparam>
		/// <param name="column"></param>
		/// <returns></returns>
		T3 Avg<T3>(T3 column);
		/// <summary>
		/// 最大值
		/// </summary>
		/// <typeparam name="T3"></typeparam>
		/// <param name="column"></param>
		/// <returns></returns>
		T3 Max<T3>(T3 column);
		/// <summary>
		/// 最小值
		/// </summary>
		/// <param name="column"></param>
		/// <returns></returns>
		T3 Min<T3>(T3 column);
	}
	public interface ISelectGroupingAggregate<TKey, TValue> : ISelectGroupingAggregate<TKey> {
		/// <summary>
		/// 所有元素
		/// </summary>
		TValue Value { get; set; }
	}
}