TableSchema

• 作为表的影子(占位符)
• 主要用来支持createtable
• 与Table一样也支持select、update、insert和delete等
• TableSchema按字段查询也是会校验的,不存在的字段会抛异常
• 本文sql示例按Sqlite数据库

1. 接口

• ITable
• ITableView
• IInsertTable
• IUpdateTable

2. TableSchema类

• 参看TableSchema

class TableSchema
    : ITable, IInsertTable, IUpdateTable, ITableView {
    string Schema { get; }
    string Name { get; }
    ColumnSchema[] Columns { get; }
    ColumnSchema[] Keys { get; }
    ColumnSchema? GetColumn(string columName);
}

3. CreateTable功能

    ColumnSchema id = new("Id", "INTEGER") { ColumnType = ColumnType.Identity | ColumnType.Key };
    ColumnSchema name = new("Name", "TEXT");
    TableSchema table = new("Students", [id, name]);
    CreateTable create = new(table);
// CREATE TABLE "Students"("Id" INTEGER PRIMARY KEY AUTOINCREMENT,"Name" TEXT)

4. DropTable功能

var drop = new DropTable("Students");
// DROP TABLE "Students"

5. 其他功能与Table类似

• 参看Table

5.1 表Schema查询示例

UserTable table = new("Users", "tenant1");
var query = new TableQuery(table)
    .And(table.Status.EqualValue(true));
var cursor = new TableCursor(query, 10, 20)
    .Desc(table.Id);
var select = new CursorSelect(cursor)
    .Select(table.Id, table.Name);
// MsSql生成sql: SELECT [Id],[Name] FROM [tenant1].[Users] WHERE [Status]=1 ORDER BY [Id] DESC OFFSET 20 ROWS FETCH NEXT 10 ROWS ONLY

public class UserTable(string tableName = "Users", string schema = "")
    : TableSchema(tableName, [Defines.Id, Defines.Name, Defines.Status], schema)
{
    #region Columns
    public readonly ColumnSchema Id = Defines.Id;
    new public readonly ColumnSchema Name  = Defines.Name;
    public readonly ColumnSchema Status = Defines.Status;
    #endregion

    class Defines
    {
        public static readonly ColumnSchema Id = new("Id") { ColumnType = ColumnType.Key };
        public static readonly ColumnSchema Name = new("Name");
        public static readonly ColumnSchema Status = new("Status");
    }
}

5.2 DDL+表达式版查询示例

var select = new TableSchema("Users", [], "tenant1")
    .ToSqlQuery<User>()
    .Where(u => u.Status)
    .Take(10, 20)
    .Desc(u => u.Id)
    .ToSelect();
// MsSql生成sql: SELECT * FROM [tenant1].[Users] WHERE [Status]=1 ORDER BY [Id] DESC OFFSET 20 ROWS FETCH NEXT 10 ROWS ONLY