多表逻辑查询

• 从多张表中按逻辑查询数据
• 是一种简化的联表查询,没有JOIN关键字
• 多表由多个别名表组成

1. 接口

• IMultiView
• IDataQuery

2. 基类

MultiTableBase

3. 类

MultiTableQuery

4. Multi

4.1 Multi扩展方法

• 从表创建MultiTableQuery

MultiTableQuery Multi(this ITable table, ITable other);

var multiTable = _db.From("Employees")
    .Multi(_db.From("Departments"));
// SELECT * FROM [Employees] AS t1,[Departments] AS t2

4.2 Multi重载扩展方法

• 从别名表创建MultiTableQuery

MultiTableQuery Multi(this IAliasTable table, IAliasTable other);

var multiTable = _db.From("Employees")
    .As("e")
    .SqlMulti(_db.From("Departments").As("d"));
// SELECT * FROM [Employees] AS e,[Departments] AS d

5. Apply扩展方法

MultiTableQuery Apply<TAliasTable>(this MultiTableQuery multiTable, string tableName, Func<Logic, TAliasTable, Logic> query)
        where TAliasTable : IAliasTable;

CommentAliasTable c = new("c");
PostAliasTable p = new("p");
var query = c.Multi(p)
    .And(c.PostId.Equal(p.Id))
    .Apply<CommentAliasTable>("c", (q, c) => q.And(c.Pick.EqualValue(true)))
    .Apply<PostAliasTable>("p", (q, p) => q.And(p.Author.EqualValue("张三")));
// SELECT * FROM [Comments] AS c,[Posts] AS p WHERE c.[PostId]=p.[Id] AND c.[Pick]=1 AND p.[Author]='张三'

6. 其他相关功能

• 本组件并非只有以上功能,其他功能参看以下文档:
• 参看MultiTableQuery的方法和扩展方法部分
• 参看查询简介
• 参看ShadowSqlCore相关文档