feat: INSERT specified columns by passing assoc array to method (#33)

* feat: named columns for INSERT statements

* feat(doc): add assoc array ref to README

README.md

@@ -112,7 +112,9 @@ $coffee = MySQL->for("beverages")->limit(1)->flatten()->select(["beverage_name",
 
 # INSERT
 
-Use `MySQL->insert()` to append a new row to a database table
+Use `MySQL->insert()` to append a new row to a database table.
+
+Passing a sequential array to `insert()` will assume that you wish to insert data for all defined columns in the table. Pass an associative array of `[column_name => value]` to INSERT data for specific columns (assuming the other columns have a [DEFAULT](https://dev.mysql.com/doc/refman/8.0/en/data-type-defaults.html) value defined).
 
 ```php
 MySQL->insert(

src/MySQL.php

@@ -279,6 +279,12 @@
 				throw new Exception("Values length does not match columns in model");
 			}
 
+			/*
+				Use array keys from $values as columns to insert if array is associative.
+				Treat statement as an all-columns INSERT if the $values array is sequential.
+			*/
+			$columns = !array_is_list($values) ? "(" . implode(",", array_keys($values)) . ")" : "";
+
 			// Convert booleans to tinyint
 			$values = self::filter_booleans($values);
 
@@ -286,7 +292,7 @@
 			$values_stmt = implode(",", array_fill(0, count($values), "?"));
 
 			// Interpolate components into an SQL INSERT statement and execute
-			$sql = "INSERT INTO {$this->table} VALUES ({$values_stmt})";
+			$sql = "INSERT INTO {$this->table} {$columns} VALUES ({$values_stmt})";
 			return $this->execute_query($sql, self::to_list_array($values));
 		}