常用表表达式,为什么用分号？

Question

通常在SQL ServerCommon Table Expression子句中,语句前面有分号,如下所示:

;WITH OrderedOrders AS --semicolon here
(
    SELECT SalesOrderID, OrderDate,
    ROW_NUMBER() OVER (ORDER BY OrderDate) AS 'RowNumber'
    FROM Sales.SalesOrderHeader 
) 
SELECT * 
FROM OrderedOrders 
WHERE RowNumber BETWEEN 50 AND 60

为什么？

Answer 1

• 避免歧义,因为WITH可以在别处使用
  ..FROM..WITH (NOLOCK)..
RESTORE..WITH MOVE..
• ;在SQL Server中终止语句是可选的

放在一起,之前的声明必须在WITH/CTE之前终止.为了避免错误,大多数人都使用,;WITH因为我们不知道CTE之前是什么

所以

DECLARE @foo int;

WITH OrderedOrders AS
(
    SELECT SalesOrderID, OrderDate,
...;

是相同的

DECLARE @foo int

;WITH OrderedOrders AS
(
    SELECT SalesOrderID, OrderDate,
...;

MERGE命令具有类似的要求.