SQL COUNT_BIG 函数

SQL Server COUNT_BIG 函数可用于计算 SELECT 语句选择的项/行的数量。它的工作方式与 Count 函数相同，但它返回 bigint。对于此 COUNT_BIG 函数，我们将使用下面提供的数据。

SQL Server COUNT_BIG (*) 示例

COUNT_BIG (*) 返回 MyEmployees 表中的总记录数。让我们看一个例子以更好地理解。

SELECT COUNT_BIG(*) AS [Number of Employees]
FROM [MyEmployees]

上面的查询将计算 MyEmployees 表中存在的总记录数

COUNT_BIG Function 2

COUNT_BIG (列名) 示例

COUNT_BIG 列名返回值不为 NULL 的记录（忽略 NULL 记录）。让我们来看一个聚合函数示例。

SELECT COUNT_BIG([EmployeeID]) AS [Number of Employees]
      ,COUNT_BIG([ManagerID]) AS [Number of Managers]	
FROM [MyEmployees]
COUNT_BIG Column Name 3

SQL 唯一 COUNT_BIG 示例

COUNT_BIG (DISTINCT 列名) 返回指定列中非 NULL 值的记录的唯一数量。 DISTINCT 关键字用于删除 SQL Server 中的重复项。

SELECT COUNT_BIG(DISTINCT [EmployeeID]) AS [Number of Unique Employees]
      ,COUNT_BIG(DISTINCT [ManagerID]) AS [Number of Unique Managers]	
FROM [MyEmployees]
Unique COUNT BIG Function 4

COUNT BIG 与 GROUP BY 子句

通常，我们编写一个 Select 查询来检查属于特定类别或颜色的产品数量等。在这些情况下，我们使用 GROUP BY 子句按颜色或类别对产品进行分组。然后，我们使用 COUNT_BIG 函数来计算该组中存在的产品的数量。让我们看一个例子。

SELECT COUNT_BIG( [EmployeeID]) AS [Number of Employees]
	  ,[Education]
      ,SUM([YearlyIncome]) AS [Total Income]
      ,SUM([Sales]) AS [Total Sale]
 FROM [MyEmployees]
 GROUP BY [Education]
 ORDER BY [Total Income] DESC
COUNT_BIG Function 5