带有COUNT帮助的SQL子查询

Question

我有一个有效的SQL语句

SELECT * FROM eventsTable WHERE columnName='Business'

我想将其添加为子查询...

COUNT(Business) AS row_count

我该怎么做呢？

Answer 1

这可能是最简单的方法,但不是最漂亮的方式:

SELECT *,
    (SELECT Count(*) FROM eventsTable WHERE columnName = 'Business') as RowCount
    FROM eventsTable
    WHERE columnName = 'Business'

这也可以在不必使用的情况下工作 group by

SELECT *, COUNT(*) OVER () as RowCount
    FROM eventsTables
    WHERE columnName = 'Business'

Answer 2

你想获得行数吗？

SELECT columnName, COUNT(*) AS row_count
FROM eventsTable
WHERE columnName = 'Business'
GROUP BY columnName

Answer 3

SELECT e.*,
       cnt.colCount 
FROM eventsTable e
INNER JOIN (
           select columnName,count(columnName) as colCount
           from eventsTable e2 
          group by columnName
           ) as cnt on cnt.columnName = e.columnName
WHERE e.columnName='Business'

- 增加了空间