单表查询

IFreeSql fsql; //如何创建请移步入门文档

class Topic
{
    [Column(IsIdentity = true)]
    public int Id { get; set; }
    public string Title { get; set; }
    public int Clicks { get; set; }
    public DateTime CreateTime { get; set; }

    public int CategoryId { get; set; }
}

单表

fsql.Select<Topic>()
    .Where(a => a.Id == 10)
    .ToList();
///SELECT a.`Id`, a.`Clicks`, a.`CategoryId`, a.`Title`, a.`CreateTime`
//FROM `Topic` a
//WHERE (a.`Id` = 10)

fsql.Select<Topic>()
    .Where(a => a.Id == 10 && a.Id > 10 || a.Clicks > 100)
    .ToList();
///SELECT a.`Id`, a.`Clicks`, a.`CategoryId`, a.`Title`, a.`CreateTime`
//FROM `Topic` a
//WHERE (a.`Id` = 10 AND a.`Id` > 10 OR a.`Clicks` > 100)

fsql.Select<Topic>()
    .Where(a => new []{1,2,3}.Contains(a.Id))
    .ToList();
//SELECT a.`Id`, a.`Clicks`, a.`CategoryId`, a.`Title`, a.`CreateTime`
//FROM `Topic` a
//WHERE (a.`Id` in (1,2,3))

WithSql

fsql.Select<Topic>()
    .WithSql("select * from Topic where clicks > @val", new { val = 10 })
    .Page(1, 10)
    .ToList()
//SELECT a.`Id`, a.`Clicks`, a.`CategoryId`, a.`Title`, a.`CreateTime` 
//FROM (select * from Topic where clicks > @val) a 

使用多次 WithSql 等于 UNION ALL 查询

v3.2.666 UnionAll 联合查询、WithTempQuery + FromQuery 嵌套查询

v3.2.666 WithMemory 使用内存数据进行查询

假设跨数据库服务器，或者数据表被缓存过，WithMemory 便可以实现数据表与内存关联查询。

var list = new List<Topic>();
list.Add(new Topic { ... });
list.Add(new Topic { ... });

fsql.Select<Topic>()
    .WithMemory(list)
    .ToList()
//SELECT a.`Id`, a.`Clicks`, a.`CategoryId`, a.`Title`, a.`CreateTime` 
//FROM (
//  SELECT ...
//  UNION ALL
//  SELECT ...
//) a