天璇翼

摘要： --选择所有字段SELECT * FROM productsgo--选择部分字段SELECT CategoryName,Description FROM Categoriesgo--不显示重复字段DISTINCTSELECT DISTINCT City as 城市 FROM Customersgo--排序[ASC|DEC]SELECT * FROM customers ORDER BY ContactName desc--分组GROUP BY--单列分组SELECT CategoryID FROM products GROUP BY CategoryID--多列分组SELECT Categor 阅读全文