add supports for increment/decrement update support

QueryBuilder.Tests/GeneralTests.cs

@@ -401,5 +401,39 @@ public void Where_Nested()
 
             Assert.Equal("SELECT * FROM [table] WHERE ([a] = 1 OR [a] = 2)", c[EngineCodes.SqlServer].ToString());
         }
+
+        [Fact]
+        public void UnsafeLiteral_Insert()
+        {
+            var query = new Query("Table").AsInsert(new
+            {
+                Count = new UnsafeLiteral("Count + 1")
+            });
+
+            var engines = new[] {
+                EngineCodes.SqlServer,
+            };
+
+            var c = Compilers.Compile(engines, query);
+
+            Assert.Equal("INSERT INTO [Table] ([Count]) VALUES (Count + 1)", c[EngineCodes.SqlServer].ToString());
+        }
+
+        [Fact]
+        public void UnsafeLiteral_Update()
+        {
+            var query = new Query("Table").AsUpdate(new
+            {
+                Count = new UnsafeLiteral("Count + 1")
+            });
+
+            var engines = new[] {
+                EngineCodes.SqlServer,
+            };
+
+            var c = Compilers.Compile(engines, query);
+
+            Assert.Equal("UPDATE [Table] SET [Count] = Count + 1", c[EngineCodes.SqlServer].ToString());
+        }
     }
 }

QueryBuilder.Tests/UpdateTests.cs

@@ -283,5 +283,37 @@ public void UpdateUsingExpandoObject()
                 "UPDATE [Table] SET [Name] = 'The User', [Age] = '2018-01-01'",
                 c[EngineCodes.SqlServer]);
         }
+
+        [Fact]
+        public void IncrementUpdate()
+        {
+            var query = new Query("Table").AsIncrement("Total");
+            var c = Compile(query);
+            Assert.Equal("UPDATE [Table] SET [Total] = [Total] + 1", c[EngineCodes.SqlServer]);
+        }
+
+        [Fact]
+        public void IncrementUpdateWithValue()
+        {
+            var query = new Query("Table").AsIncrement("Total", 2);
+            var c = Compile(query);
+            Assert.Equal("UPDATE [Table] SET [Total] = [Total] + 2", c[EngineCodes.SqlServer]);
+        }
+
+        [Fact]
+        public void IncrementUpdateWithWheres()
+        {
+            var query = new Query("Table").Where("Name", "A").AsIncrement("Total", 2);
+            var c = Compile(query);
+            Assert.Equal("UPDATE [Table] SET [Total] = [Total] + 2 WHERE [Name] = 'A'", c[EngineCodes.SqlServer]);
+        }
+
+        [Fact]
+        public void DecrementUpdate()
+        {
+            var query = new Query("Table").Where("Name", "A").AsDecrement("Total", 2);
+            var c = Compile(query);
+            Assert.Equal("UPDATE [Table] SET [Total] = [Total] - 2 WHERE [Name] = 'A'", c[EngineCodes.SqlServer]);
+        }
     }
 }

QueryBuilder/Clauses/IncrementClause.cs

@@ -0,0 +1,19 @@
+namespace SqlKata
+{
+    public class IncrementClause : InsertClause
+    {
+        public string Column { get; set; }
+        public int Value { get; set; } = 1;
+
+        public override AbstractClause Clone()
+        {
+            return new IncrementClause
+            {
+                Engine = Engine,
+                Component = Component,
+                Column = Column,
+                Value = Value
+            };
+        }
+    }
+}

QueryBuilder/Compilers/Compiler.cs

@@ -285,25 +285,48 @@ protected virtual SqlResult CompileUpdateQuery(Query query)
                 throw new InvalidOperationException("Invalid table expression");
             }
 
-            var toUpdate = ctx.Query.GetOneComponent<InsertClause>("update", EngineCode);
+            // check for increment statements
+            var clause = ctx.Query.GetOneComponent("update", EngineCode);
+
+            string wheres;
+
+            if (clause != null && clause is IncrementClause increment)
+            {
+                var column = Wrap(increment.Column);
+                var value = Parameter(ctx, Math.Abs(increment.Value));
+                var sign = increment.Value >= 0 ? "+" : "-";
+
+                wheres = CompileWheres(ctx);
 
+                if (!string.IsNullOrEmpty(wheres))
+                {
+                    wheres = " " + wheres;
+                }
+
+                ctx.RawSql = $"UPDATE {table} SET {column} = {column} {sign} {value}{wheres}";
+
+                return ctx;
+            }
+
+
+            var toUpdate = ctx.Query.GetOneComponent<InsertClause>("update", EngineCode);
             var parts = new List<string>();
 
             for (var i = 0; i < toUpdate.Columns.Count; i++)
             {
                 parts.Add(Wrap(toUpdate.Columns[i]) + " = " + Parameter(ctx, toUpdate.Values[i]));
             }
 
-            var where = CompileWheres(ctx);
+            var sets = string.Join(", ", parts);
 
-            if (!string.IsNullOrEmpty(where))
+            wheres = CompileWheres(ctx);
+
+            if (!string.IsNullOrEmpty(wheres))
             {
-                where = " " + where;
+                wheres = " " + wheres;
             }
 
-            var sets = string.Join(", ", parts);
-
-            ctx.RawSql = $"UPDATE {table} SET {sets}{where}";
+            ctx.RawSql = $"UPDATE {table} SET {sets}{wheres}";
 
             return ctx;
         }

QueryBuilder/Query.Update.cs

@@ -54,5 +54,22 @@ public Query AsUpdate(IEnumerable<KeyValuePair<string, object>> values)
 
             return this;
         }
+
+        public Query AsIncrement(string column, int value = 1)
+        {
+            Method = "update";
+            AddOrReplaceComponent("update", new IncrementClause
+            {
+                Column = column,
+                Value = value
+            });
+
+            return this;
+        }
+
+        public Query AsDecrement(string column, int value = 1)
+        {
+            return AsIncrement(column, -value);
+        }
     }
 }