Implement CONCAT function

query_executors/memory_executor/memory_executor.go

@@ -180,6 +180,8 @@ func getFieldValue(field parsers.SelectItem, queryParameters map[string]interfac
 			return strings_StringEquals(typedValue.Arguments, queryParameters, row)
 		case parsers.FunctionCallIsDefined:
 			return typeChecking_IsDefined(typedValue.Arguments, queryParameters, row)
+		case parsers.FunctionCallConcat:
+			return strings_Concat(typedValue.Arguments, queryParameters, row)
 		}
 	}
 

query_executors/memory_executor/memory_executor_string_functions_test.go

@@ -103,4 +103,52 @@ func Test_Execute_StringFunctions(t *testing.T) {
 			},
 		)
 	})
+
+	t.Run("Should execute function CONCAT()", func(t *testing.T) {
+		testQueryExecute(
+			t,
+			parsers.SelectStmt{
+				SelectItems: []parsers.SelectItem{
+					{
+						Alias: "concat",
+						Type:  parsers.SelectItemTypeFunctionCall,
+						Value: parsers.FunctionCall{
+							Type: parsers.FunctionCallConcat,
+							Arguments: []interface{}{
+								parsers.SelectItem{
+									Path: []string{"c", "id"},
+									Type: parsers.SelectItemTypeField,
+								},
+								parsers.SelectItem{
+									Type: parsers.SelectItemTypeConstant,
+									Value: parsers.Constant{
+										Type:  parsers.ConstantTypeString,
+										Value: " ",
+									},
+								},
+								parsers.SelectItem{
+									Type: parsers.SelectItemTypeConstant,
+									Value: parsers.Constant{
+										Type:  parsers.ConstantTypeString,
+										Value: 123,
+									},
+								},
+								parsers.SelectItem{
+									Path: []string{"c", "pk"},
+									Type: parsers.SelectItemTypeField,
+								},
+							},
+						},
+					},
+				},
+				Table: parsers.Table{Value: "c"},
+			},
+			mockData,
+			[]memoryexecutor.RowType{
+				map[string]interface{}{"concat": "123 123aaa"},
+				map[string]interface{}{"concat": "456 123bbb"},
+				map[string]interface{}{"concat": "789 123AAA"},
+			},
+		)
+	})
 }

query_executors/memory_executor/string_functions.go

@@ -39,3 +39,28 @@ func strings_StringEquals(arguments []interface{}, queryParameters map[string]in
 
 	return str1 == str2
 }
+
+func strings_Concat(arguments []interface{}, queryParameters map[string]interface{}, row RowType) string {
+	result := ""
+
+	for _, arg := range arguments {
+		if selectItem, ok := arg.(parsers.SelectItem); ok {
+			value := getFieldValue(selectItem, queryParameters, row)
+			result += convertToString(value)
+		}
+	}
+
+	return result
+}
+
+func convertToString(value interface{}) string {
+	switch v := value.(type) {
+	case string:
+		return v
+	case int:
+		return fmt.Sprintf("%d", v)
+	case float32, float64:
+		return fmt.Sprintf("%f", v)
+	}
+	return ""
+}