我正在读取其他人编写的TSQL代码,并发现有点奇怪的语法。它正在按字符串排序。我做了一些测试,下面是代码。任何人都可以帮我解释一下吗?谢谢。SQL Server按语法排序时的顺序当和常量
首先查询
SELECT *
FROM dbo.Products
结果:
ProductID ProductName SupplierID CategoryID QuantityPerUnit UnitPrice UnitsInStock UnitsOnOrder ReorderLevel Discontinued
----------- ------------------------------- ----------- ----------- -------------------- --------------------- ------------ ------------ ------------ ------------
1 Chai 1 1 10 boxes x 20 bags 18.00 39 0 10 0
2 Chang 1 1 24 - 12 oz bottles 19.00 17 40 25 0
3 Aniseed Syrup 1 2 12 - 550 ml bottles 10.00 13 70 25 0
4 Chef Anton's Cajun Seasoning 2 2 48 - 6 oz jars 22.00 53 0 0 0
...
*/
第二个查询:
SELECT *
FROM dbo.Products
WHERE ProductID < 10
ORDER BY '3';
结果:
消息408,级别16,状态1,1 ORDER BY列表时遇到一个常量表达式 线,位置1
第三查询
SELECT *
FROM dbo.Products
WHERE ProductID < 10
ORDER BY CASE WHEN SupplierID = 2 THEN '1'
WHEN SupplierID = 1 THEN '2'
ELSE '3'
END;
结果:
ProductID ProductName SupplierID CategoryID QuantityPerUnit UnitPrice UnitsInStock UnitsOnOrder ReorderLevel Discontinued
----------- ---------------------------------------- ----------- ----------- -------------------- --------------------- ------------ ------------ ------------ ------------
4 Chef Anton's Cajun Seasoning 2 2 48 - 6 oz jars 22.00 53 0 0 0
5 Chef Anton's Gumbo Mix 2 2 36 boxes 21.35 0 0 0 1
1 Chai 1 1 10 boxes x 20 bags 18.00 39 0 10 0
2 Chang 1 1 24 - 12 oz bottles 19.00 17 40 25 0
3 Aniseed Syrup 1 2 12 - 550 ml bottles 10.00 13 70 25 0
6 Grandma's Boysenberry Spread 3 2 12 - 8 oz jars 25.00 120 0 25 0
7 Uncle Bob's Organic Dried Pears 3 7 12 - 1 lb pkgs. 30.00 15 0 10 0
8 Northwoods Cranberry Sauce 3 2 12 - 12 oz jars 40.00 6 0 0 0
9 Mishi Kobe Niku 4 6 18 - 500 g pkgs. 97.00 29 0 0 1
(9 row(s) affected)
*/
谢谢,明确的解释。 – 2012-03-24 10:00:11