联表

• 从联表获取数据组件
• 本组件用来处理sql的SELECT语句
• 本组件是对ShadowSql.Core同名组件的扩展

1. 接口

ISelect

2. 基类

• SelectFieldsBase

3. 类

MultiTableSelect

4. ToSelect

创建MultiTableSelect

MultiTableSelect ToSelect(this IMultiView table);
MultiTableSelect ToSelect(this IJoinOn table);

注:不能从IJoin对象获取数据,它的ToSelect实际是操作他的Root联表对象

4.1 从sql联表获取

• 依赖sql联表

CommentAliasTable c = new("c");
PostAliasTable p = new("p");
var select = c.SqlJoin(p)
    .And(c.PostId, p.Id)
    .Root
    .ToSelect();
// SELECT * FROM [Comments] AS c INNER JOIN [Posts] AS p ON c.[PostId]=p.[Id]

4.2 从sql多表获取

• 依赖sql多表

CommentAliasTable c = new("c");
PostAliasTable p = new("p");
var select = c.SqlMulti(p)
    .Where(c.PostId.Equal(p.Id))
    .ToSelect();
// SELECT * FROM [Comments] AS c,[Posts] AS p WHERE c.[PostId]=p.[Id]

4.3 从逻辑联表获取

• 依赖逻辑联表

CommentAliasTable c = new("c");
PostAliasTable p = new("p");
var select = c.Join(p)
    .And(c.PostId.Equal(p.Id))
    .Root
    .ToSelect();
// SELECT * FROM [Comments] AS c INNER JOIN [Posts] AS p ON c.[PostId]=p.[Id]

4.4 从逻辑多表获取

• 依赖逻辑多表

CommentAliasTable c = new("c");
PostAliasTable p = new("p");
var select = c.Multi(p)
    .And(c.PostId.Equal(p.Id))
    .ToSelect();
// SELECT * FROM [Comments] AS c,[Posts] AS p WHERE c.[PostId]=p.[Id]

5. Select

5.1 Select方法

• 从表筛选字段

MultiTableSelect Select<TTable>(string tableName, Func<TTable, IColumn> select)
        where TTable : ITable;
MultiTableSelect Select<TTable>(string tableName, Func<TTable, IEnumerable<IColumn>> select)
        where TTable : ITable;

var select = new CommentTable()
    .SqlJoin(new PostTable())
    .On(t1 => t1.PostId, t2 => t2.Id)
    .ToSelect()
    .Select<CommentTable>("Comments", t1 => t1.Content);
// SELECT t1.[Content] FROM [Comments] AS t1 INNER JOIN [Posts] AS t2 ON t1.[PostId]=t2.[Id]

var select = new CommentTable()
    .SqlJoin(new PostTable())
    .On(t1 => t1.PostId, t2 => t2.Id)
    .ToSelect()
    .Select<CommentTable>("Comments", t1 => [t1.Id, t1.Content]);
// SELECT t1.[Id],t1.[Content] FROM [Comments] AS t1 INNER JOIN [Posts] AS t2 ON t1.[PostId]=t2.[Id]

5.2 Select重载方法

• 从别名表筛选字段

MultiTableSelect Select<TAliasTable>(string tableName, Func<TAliasTable, IFieldView> select)
        where TAliasTable : IAliasTable;
MultiTableSelect Select<TAliasTable>(string tableName, Func<TAliasTable, IEnumerable<IFieldView>> select)
        where TAliasTable : IAliasTable;

var select = new CommentAliasTable("c")
    .SqlJoin(new PostAliasTable("p"))
    .On(c => c.PostId, p => p.Id)
    .ToSelect()
    .Select<CommentAliasTable>("Comments", c => c.Content);
// SELECT c.[Content] FROM [Comments] AS c INNER JOIN [Posts] AS p ON c.[PostId]=p.[Id]

var select = new CommentAliasTable("c")
    .SqlJoin(new PostAliasTable("p"))
    .On(c => c.PostId, p => p.Id)
    .ToSelect()
    .Select<CommentAliasTable>("Comments", c => [c.Id, c.Content]);
// SELECT c.[Id],c.[Content] FROM [Comments] AS c INNER JOIN [Posts] AS p ON c.[PostId]=p.[Id]

6. SelectTable扩展方法

筛选别名表

TMultiTableSelect SelectTable<TMultiTableSelect>(this TMultiTableSelect multiSelect, IAliasTable aliasTable)
        where TMultiTableSelect : MultiSelectBase;
TMultiTableSelect SelectTable<TMultiTableSelect>(this TMultiTableSelect multiSelect, string tableName)
        where TMultiTableSelect : MultiSelectBase;

CommentAliasTable c = new("c");
PostAliasTable p = new("p");
var select = c.SqlJoin(p)
    .On(c.PostId, p.Id)
    .ToSelect()
    .SelectTable(c);
// SELECT c.* FROM [Comments] AS c INNER JOIN [Posts] AS p ON c.[PostId]=p.[Id]

var select = new Table("Comments")
    .SqlJoin(new Table("Posts"))
    .OnColumn("PostId", "Id")
    .ToSelect()
    .SelectTable("Comments");
// SELECT t1.* FROM [Comments] AS t1 INNER JOIN [Posts] AS t2 ON t1.[PostId]=t2.[Id]

7. 其他相关功能

• 参看获取简介
• 参看sql联表
• 参看sql多表
• 参看逻辑联表
• 参看逻辑多表
• 参看ShadowSqlCore相关文档