select row_number() over() as

This is not a complete SQL statement. It looks like it is the beginning of a window function that assigns a row number to each row in a query result set.

The full syntax for this statement would be:

SELECT ROW_NUMBER() OVER (ORDER BY column_name) AS row_num, column1, column2, ...
FROM table_name

This statement would assign a unique row number to each row in the query result set, based on the order specified by the column_name in the ORDER BY clause. The row number would be assigned to a new column called row_num, and the other columns in the SELECT statement would be included as well.

相关问题

怎么优化下面SQL： select distinct bid from ( select row_number() over(order by bid,start_date) as num,bid,start_date,end_date from t1 )a inner join ( select row_number() over(order by bid,start_date) as num,bid,start_date,end_date from t1 )b on a.bid = b.bid where a.num = b.num+1

可以考虑使用CTE（公共表表达式）来优化该SQL语句。具体做法如下：

WITH cte AS (
  SELECT ROW_NUMBER() OVER (ORDER BY bid, start_date) AS num, bid, start_date, end_date
  FROM t1
)
SELECT DISTINCT a.bid
FROM cte a
INNER JOIN cte b ON a.bid = b.bid AND a.num = b.num + 1

使用公共表表达式的好处是可以避免重复计算，使得SQL语句更加简洁和易于理解。在这个例子中，我们只需要计算一次ROW_NUMBER()函数，然后在CTE中引用它即可。同时，使用WITH语句也可以使得SQL语句更加可读性强，更加易于维护。

SELECT row_number() over

引用\[1\]和\[2\]提供了使用row_number()函数对订单进行编号，并按照订单时间倒序的示例代码。这个函数可以在SELECT语句中使用，通过在ORDER BY子句中指定排序的列和顺序来对结果集进行编号。在这个例子中，使用了ROW_NUMBER() over (order by OrderTime desc) as rowIndex来为每个订单分配一个行号，并按照订单时间倒序排列。引用\[3\]提供了另一种分页的示例代码，使用了OFFSET和FETCH NEXT子句来实现。在这个例子中，使用了OFFSET (pageindex-1) * pagesize rows fetch pagesize rows only来指定要返回的行数和偏移量。请注意，这个语法只适用于SQL Server 2012及以上版本。
#### 引用[.reference_title]
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