feat(command): allow join of tables on itself

README.md

@@ -76,6 +76,35 @@ public class ExamplesRepository : IExamplesRepository
 }
 ```
 
+You can also join a table on itself:
+
+```c#
+using System;
+using Snowflake.Data.Xt;
+
+namespace SnowflakeApplication;
+
+[SnowflakeTable(
+  name: "COST_CENTER",
+  alias: "costCenter1")]
+[SnowflakeJoin(
+  table: "COST_CENTER",
+  alias: "costCenter2",
+  type: SnowflakeJoinAttribute.Left,
+  condition: "costCenter1.COST_CENTER_ID = costCenter2.COST_CENTER_ID")]
+public class Example
+{
+  [SnowflakeColumn(name: "VALUE")]
+  public decimal Value { get; set; }
+
+  [SnowflakeColumn(name: "ADDRESS", table: "COST_CENTER")]
+  public string Address { get; set; }
+
+  [SnowflakeColumn(name: "IS_READY", table: "COST_CENTER", alias: "costCenter2")] // Alias must be provided
+  public bool IsReady { get; set; }
+}
+```
+
 You can also reuse a snowflake database connection:
 
 ```c#

src/Attributes/SnowflakeColumnAttribute.cs

@@ -18,12 +18,19 @@ public sealed class SnowflakeColumnAttribute : Attribute
   /// </summary>
   /// <param name="name">The name.</param>
   /// <param name="table">The table.</param>
-  public SnowflakeColumnAttribute(string? name = default, string? table = default)
+  /// <param name="alias">The alias.</param>
+  public SnowflakeColumnAttribute(string? name = default, string? table = default, string? alias = default)
   {
+    this.Alias = alias;
     this.Name = name ?? string.Empty;
     this.Table = table;
   }
 
+  /// <summary>
+  /// Gets the alias.
+  /// </summary>
+  public string? Alias { get; internal set; }
+
   /// <summary>
   /// Gets the name.
   /// </summary>

src/Command/SnowflakeCommand.cs

@@ -184,8 +184,9 @@ protected string Columns
       {
         var column = property.Value;
         var table = column.Table ?? this.Table.Name;
-        var tableAlias = string.Equals(this.Table.Name, table, StringComparison.Ordinal) ? this.Table.Alias ?? string.Empty
-          : this.Joins.SingleOrDefault(join => string.Equals(join.Table, table, StringComparison.Ordinal))?.Alias ?? string.Empty;
+        var tableAlias = column.Alias ?? (string.Equals(this.Table.Name, table, StringComparison.Ordinal)
+          ? this.Table.Alias ?? string.Empty
+          : this.Joins.SingleOrDefault(join => string.Equals(join.Table, table, StringComparison.Ordinal))?.Alias ?? string.Empty);
 
         columns.Append($"{tableAlias}{(string.IsNullOrWhiteSpace(tableAlias) ? string.Empty : ".")}{column.Name}, ");
       }

tests/Command/SnowflakeCommand.Tests.cs

@@ -27,4 +27,17 @@ public void Constructor_ShouldFill_SELECT_FROM_JOIN_ForClassWithJoin()
     // Assert
     sql.Should().Be("SELECT bar.ID, foo.PROP_1, bar.Prop_2 FROM DATABASE.SCHEMA.BAR AS bar LEFT JOIN DATABASE.SCHEMA.FOO AS foo ON bar.ID = foo.ID");
   }
+
+  [Fact]
+  public void Constructor_ShouldFill_SELECT_FROM_JOIN_ForClassWithJoinOnItself()
+  {
+    // Arrange
+    var command = new SnowflakeCommand<SnowflakeClass3>("DATABASE", "SCHEMA");
+
+    // Act
+    var sql = command.Sql;
+
+    // Assert
+    sql.Should().Be("SELECT bar1.ID, bar1.PROP_1, bar2.Prop_2 FROM DATABASE.SCHEMA.BAR AS bar1 LEFT JOIN DATABASE.SCHEMA.BAR AS bar2 ON bar1.ID = bar2.ID");
+  }
 }

tests/TestClasses.cs

@@ -29,3 +29,23 @@ internal sealed class SnowflakeClass2
   [SnowflakeColumn]
   public string? Prop_2 { get; set; }
 }
+
+[SnowflakeTable(
+  name: "BAR",
+  alias: "bar1")]
+[SnowflakeJoin(
+  table: "BAR",
+  alias: "bar2",
+  type: SnowflakeJoinAttribute.Left,
+  condition: "bar1.ID = bar2.ID")]
+internal sealed class SnowflakeClass3
+{
+  [SnowflakeColumn("ID")]
+  public int Id { get; set; }
+
+  [SnowflakeColumn("PROP_1", "BAR")]
+  public string? Property1 { get; set; }
+
+  [SnowflakeColumn("Prop_2", "BAR", "bar2")]
+  public string? Prop_2 { get; set; }
+}