Question

我的数据格式如下：

c_time,             c_id
-------------------------
2009-01-01 12:30,   123
2009-01-01 12:31,   125
2009-01-01 12:32,   123

2009-01-02 12:31,   124
2009-01-02 12:32,   123
2009-01-02 12:33,   124

id对应于文本中的值。

如何编写查询以计算每个日期的出现次数？
如何将ID替换为对应的文本（相当于excel vlookup）？

我试图编写查询，并且想看看其他人会怎么做。

Answer 1

select date, count(distinct id)
from tbl
group by cast(date as date) --this forces to remove the time

Answer 2

MySQL查询 select count(id),date from <your_table_name> group by date

Answer 3

使用SSMS作为DBMS。

您还可以利用COUNT()，OVER()，common table expession和DISTINCT的优势。

--Creating the table to hold your values 
CREATE TABLE #tmpTable (
[date] DATE,
[time] TIME,
[id] BIGINT
)
-- Inserting values
INSERT INTO #tmpTable
VALUES 
('2009-01-01', '12:30', 123),
('2009-01-01', '12:31', 125 ),
('2009-01-01', '12:32', 123 ),
('2009-01-02', '12:31', 124 ),
('2009-01-02', '12:32', 123 ),  
('2009-01-02', '12:33', 124 )

-- Common table expression
WITH CTE 
AS 
(SELECT [date], [time], [id], COUNT([date]) OVER(Partition by [date],[id] order by 
[id]) AS rn FROM #tmpTable
)

SELECT DISTINCT [date], [id], [rn] 
FROM CTE 
ORDER BY id

有没有办法使用SQL？

3 个答案: