Support separate From() Expressions in SqlExpressions, previously coupled to Select()

Author: mythz

src/ServiceStack.OrmLite/Expressions/SqlExpression.cs

@@ -9,11 +9,12 @@
 
 namespace ServiceStack.OrmLite
 {
-    public abstract class SqlExpression<T>
+    public abstract class SqlExpression<T> : ISqlExpression
     {
         private Expression<Func<T, bool>> underlyingExpression;
         private List<string> orderByProperties = new List<string>();
         private string selectExpression = string.Empty;
+        private string fromExpression = null;
         private string whereExpression;
         private string groupBy = string.Empty;
         private string havingExpression;
@@ -47,6 +48,7 @@ protected virtual SqlExpression<T> CopyTo(SqlExpression<T> to)
             to.underlyingExpression = underlyingExpression;
             to.orderByProperties = orderByProperties;
             to.selectExpression = selectExpression;
+            to.fromExpression = fromExpression;
             to.whereExpression = whereExpression;
             to.groupBy = groupBy;
             to.havingExpression = havingExpression;
@@ -112,6 +114,30 @@ public virtual SqlExpression<T> SelectDistinct<TKey>(Expression<Func<T, TKey>> f
             return this;
         }
 
+        public virtual SqlExpression<T> From(string tables)
+        {
+            if (string.IsNullOrEmpty(tables))
+            {
+                FromExpression = null;
+            }
+            else
+            {
+                tables.SqlVerifyFragment();
+                var singleTable = tables.ToLower().IndexOfAny("join", ",") >= 0;
+                FromExpression = singleTable
+                    ? " \nFROM " + OrmLiteConfig.DialectProvider.GetQuotedTableName(tables)
+                    : " \nFROM " + tables;
+            }
+
+            return this;
+        }
+
+        public virtual SqlExpression<T> From<Table>()
+        {
+            FromExpression = " \nFROM " + OrmLiteConfig.DialectProvider.GetQuotedTableName(typeof(Table).GetModelDefinition());
+            return this;
+        }
+
         public virtual SqlExpression<T> Where()
         {
             if (underlyingExpression != null) underlyingExpression = null; //Where() clears the expression
@@ -457,6 +483,9 @@ public virtual string ToSelectStatement()
             var sql = new StringBuilder();
 
             sql.Append(SelectExpression);
+
+            sql.Append(FromExpression);
+
             sql.Append(string.IsNullOrEmpty(WhereExpression) ?
                        "" :
                        "\n" + WhereExpression);
@@ -492,6 +521,17 @@ public string SelectExpression
             }
         }
 
+        public string FromExpression
+        {
+            get
+            {
+                return string.IsNullOrEmpty(fromExpression)
+                    ? " \nFROM " + OrmLiteConfig.DialectProvider.GetQuotedTableName(modelDef)
+                    : fromExpression;
+            }
+            set { fromExpression = value; }
+        }
+
         public string WhereExpression
         {
             get
@@ -1035,13 +1075,11 @@ protected static object GetQuotedFalseValue()
 
         private void BuildSelectExpression(string fields, bool distinct)
         {
-
-            selectExpression = string.Format("SELECT {0}{1} \nFROM {2}",
+            selectExpression = string.Format("SELECT {0}{1}",
                 (distinct ? "DISTINCT " : ""),
                 (string.IsNullOrEmpty(fields) ?
                     OrmLiteConfig.DialectProvider.GetColumnNames(modelDef) :
-                    fields),
-                OrmLiteConfig.DialectProvider.GetQuotedTableName(modelDef));
+                    fields));
         }
 
         public IList<string> GetAllFields()
@@ -1263,6 +1301,11 @@ protected virtual object VisitColumnAccessMethod(MethodCallExpression m)
         }
     }
 
+    public interface ISqlExpression
+    {
+        string ToSelectStatement();
+    }
+
     public class PartialSqlString
     {
         public PartialSqlString(string text)

tests/ServiceStack.OrmLite.Tests/Expression/FromExpressionTests.cs

@@ -0,0 +1,40 @@
+using System.Data;
+using NUnit.Framework;
+using ServiceStack.OrmLite.Tests.Shared;
+
+namespace ServiceStack.OrmLite.Tests.Expression
+{
+    public class Band
+    {
+        public string Name { get; set; }
+        public int PersonId { get; set; }
+    }
+
+    public class FromExpressionTests : ExpressionsTestBase
+    {
+        public void Init(IDbConnection db)
+        {
+            db.DropAndCreateTable<Person>();
+            db.DropAndCreateTable<Band>();
+
+            db.InsertAll(Person.Rockstars);
+
+            db.Insert(new Band { Name = "The Doors", PersonId = 3 });
+            db.Insert(new Band { Name = "Nirvana", PersonId = 4 });
+        }
+
+        [Test]
+        public void Can_select_from_custom_FROM_expression()
+        {
+            using (var db = OpenDbConnection())
+            {
+                Init(db);
+
+                var results = db.Select(db.From<Person>("Person INNER JOIN Band ON Person.Id = Band.PersonId"));
+
+                Assert.That(results.Count, Is.EqualTo(2));
+                Assert.That(results.ConvertAll(x => x.FirstName), Is.EquivalentTo(new[] { "Kurt", "Jim" }));
+            }
+        }
+    }
+}