ShadowSql之表达式树

ShadowSql的主要思想通过表和字段的影子来拼写sql

.net中的表达式树是作为模型类的影子,非常契合ShadowSql

拿表达式树来拼写sql就和EF类似

一、nuget包

nuget安装ShadowSql.Expressions

引用命名空间: ShadowSql.Expressions

二、简单用法

1. 表达式查询
1.1 按常量查询

var query = new TableSqlQuery<User>("Users")
.Where(u => u.Name == "张三");
// SELECT * FROM [Users] WHERE [Name]='张三'

1.2 按参数查询

var query = new TableSqlQuery<User>()
.Where<UserParameter>((u, p) => u.Age > p.Age2);
// SELECT * FROM [User] WHERE [Age]>@Age2

2. 表达式排序
2.1 对单个字段排序

var cursor = new Table("Users")
.Take<User>(10)
.Asc(u => u.Id);
// SELECT TOP 10 * FROM [Users] ORDER BY [Id]

2.2 对多个字段排序

var cursor = new Table("Users")
.Take<User>(10)
.Desc(u => new { u.Age, u.Id });
// SELECT TOP 10 * FROM [Users] ORDER BY [Age] DESC,[Id] DESC

3. 联表查询
3.1 主外键联表

var query = new Table("Users")
    .SqlJoin<User, UserRole>(new Table("UserRoles"))
    .On(u => u.Id, r => r.UserId);
// SELECT * FROM [Users] AS t1 INNER JOIN [UserRoles] AS t2 ON t1.[Id]=t2.[UserId]

3.2 逻辑表达式联表

var query = new Table("Users")
    .SqlJoin<User, UserRole>(new Table("UserRoles"))
    .On((u, r) => u.Id == r.UserId);
// SELECT * FROM [Users] AS t1 INNER JOIN [UserRoles] AS t2 ON t1.[Id]=t2.[UserId]

4. 插入
4.1 插入常量值

var insert = EmptyTable.Use("Users")
.ToInsert(() => new User { Name = "张三", Age = 18 });
// INSERT INTO [Users]([Name],[Age])VALUES('张三',18)

4.2 插入参数

var insert = EmptyTable.Use("Users")
    .ToInsert<UserParameter, User>(p => new User { Name = p.Name2, Age = p.Age2 });
// INSERT INTO [Users]([Name],[Age])VALUES(@Name2,@Age2)

5. 表达式删除

var delete = new TableSqlQuery<Student>("Students")
    .Where(s => s.Score < 60)
    .ToDelete();
// DELETE FROM [Students] WHERE [Score]<60

6. 表达式更新
6.1 常量更新

var update = EmptyTable.Use("Users")
    .ToUpdate<User>(u => u.Id == 1)
    .Set(u => new User { Age = 18 });
// UPDATE [Users] SET [Age]=18 WHERE [Id]=1

6.2 参数化更新

var user = new User { Id =1, Age = 18 };
var update = EmptyTable.Use("Users")
    .ToUpdate<User>(u => u.Id == user.Id)
    .Set(u => new User { Age = user.Age });
// UPDATE [Users] SET [Age]=@Age WHERE [Id]=@Id

6.3 原值叠加更新

var update = EmptyTable.Use("Students")
    .ToUpdate<Student>(u => u.Score < 60 && u.Score > 55)
    .Set(u => new Student { Score = u.Score + 5 });
// UPDATE [Students] SET [Score]=([Score]+5) WHERE [Score]<60 AND [Score]>55

7、表达式获取数据
7.1 直接获取全表

var select = _db.From("Users")
    .ToSelect<User>()
    .Select(u => new { u.Id, u.Name });
// SELECT [Id],[Name] FROM [Users]

7.3 从表达式获取

var select = _db.From("Users")
    .ToSelect<User>(u => u.Status)
    .Select(u => u.Id);
// SELECT [Id] FROM [Users] WHERE [Status]=1

7.3 从表查询获取

var select = _db.From("Users")
    .ToSqlQuery<User>()
    .Where(u => u.Status)
    .ToSelect()
    .Select(u => new { u.Id, u.Name });
// SELECT [Id],[Name] FROM [Users] WHERE [Status]=1

7.4 分页获取

var select = _db.From("Users")
    .ToSqlQuery<User>()
    .Where(u => u.Status)
    .Take(10, 20)
    .Desc(u => u.Id)
    .ToSelect();
// SELECT * FROM [Users] WHERE [Status]=1 ORDER BY [Id] OFFSET 20 ROWS FETCH NEXT 10 ROWS ONLY

欢迎大家尝试,有什么问题给我留言,我会尽力满足大家的需求

源码托管地址: https://github.com/donetsoftwork/Shadow，也欢迎大家直接查看源码。

文档地址: https://donetsoftwork.github.io/Shadow/expression/index.html
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