sql - 在预期条件的上下文中指定的非布尔类型的表达式

Question

我厌倦了看到这个错误：

消息 102，级别 15，状态 1，过程 sp_reorder_quantity，第 16 行
“–”附近的语法不正确。

它说明了这一点，因为在第 16 行它指出：

WHERE products.quantity_in_stock – products.reorder_level < @unit; 

据说products.quantity_in_stock是：An expression of non-boolean type specified in a context where a condition is expected。

CREATE PROCEDURE sp_reorder_quantity
(
    @unit       int
)
AS
   SELECT
      products.product_id,
      suppliers.name,
      suppliers.address,
      suppliers.city,
      suppliers.province,
      'qty' = products.quantity_in_stock,
      products.reorder_level
   FROM
      suppliers
   INNER JOIN
      products ON suppliers.supplier_id = products.supplier_id
   WHERE
      products.quantity_in_stock – products.reorder_level < @unit;
GO

Answer 1

Answer 2

You can always rephrase the line as:

WHERE                   products.quantity_in_stock < products.reorder_level + @unit;