MySQL -对当前行执行计数(*)

Here's my SELECT query:

这是我选择查询:

SELECT col1, col3, col5, col8
FROM Table1

In my SELECT query, I want to perform a COUNT(*) exclusively for the current row.

在SELECT查询中，我希望为当前行执行一个COUNT(*)。

I want something like this, but have no idea how I can get this:

我想要这样的东西，但不知道我怎么能得到这个:

SELECT col1, col3, 
(
SELECT COUNT(*) 
FROM table1 WHERE col3 = col3 value for current row
), 
col5, col8
FROM Table1

What is the correct way to perform a COUNT(*) for the current row of a SELECT query resultset?

对于选择查询结果集的当前行执行计数(*)的正确方法是什么?

3 个解决方案

#1

try this:

试试这个:

set @num := 0;
SELECT @num := @num+1 , col1, col3, col5, col8 FROM Table1

or other way:

或其他方式:

SET @num := ( SELECT COUNT( * ) FROM Table1) ;
SELECT @num := @num -1 , col1, col3, col5, col8
FROM Table1

#2

SELECT col1, col3, 
(
    SELECT COUNT(*) 
    FROM table1 WHERE id = A.Id
) Count, 
col5, col8
FROM Table1 A

#3

Found it.

找到了。

If I write my query like this:

如果我这样写我的查询:

SELECT col1, col3, 
COUNT(*) AS count,
col5, col8
FROM Table1

then I get COUNT of all the items in Table1 for all rows.

然后计算表1中所有行的所有项。

I actually wanted COUNT of all items for selective rows.

实际上，我想要为选择行计算所有项的数量。

Like I may have col3 value appearing more than once. I actually want the count of all items for each col3.

就像我可能有col3值不止一次出现一样。实际上，我想要每个col3的所有项的计数。

So, GROUP BY clause is the solution.

所以，GROUP BY子句是解。

SELECT col1, col3, 
COUNT(*) AS Count, 
col5, col8
FROM Table1 
GROUP BY col3

Sorry, I think I wasn't able to explain my problem properly, so it confused a lot of people.. A very poor question. My bad.

对不起，我想我不能正确地解释我的问题，所以它使很多人困惑。一个很差的问题。我的坏。

#1