Question

我的数据没有关系。只需要计算3个表中的各个列，并将它们作为视图显示在页面上。

到目前为止，这是代码，但不起作用：

SELECT COUNT(cars) AS A,
       (SELECT COUNT(boats) FROM tableBoats) AS B,
       (SELECT COUNT(trees) FROM tableTrees) AS C,
 FROM tableCars

Answer 1

SELECT A, B, C
FROM (SELECT COUNT(cars) as A FROM tableCars) a
CROSS JOIN (SELECT COUNT(boats) as B FROM tableBoats) b
CROSS JOIN (SELECT COUNT(trees) as C FROM tableTrees) c

应该这样做。

Answer 2

假设你有一个像这里的表（tableXxx表有一个名为xxx的字段），你的查询在AS C,之后有一个逗号，没有逗号，它有语法错误，它工作正常（至少使用sqlite，因为mssql不能在sqlfiddle上工作）：

http://sqlfiddle.com/#!5/5fa6c/3

SELECT COUNT(cars) AS A,
       (SELECT COUNT(boats) FROM tableBoats) AS B,
       (SELECT COUNT(trees) FROM tableTrees) AS C
FROM tableCars

顺便说一句，您可以将查询简化为

SELECT (SELECT COUNT(cars ) FROM tableCars ) AS A,
       (SELECT COUNT(boats) FROM tableBoats) AS B,
       (SELECT COUNT(trees) FROM tableTrees) AS C

其他答案也很完美：）

Answer 3

这个怎么样？

SELECT
    (SELECT COUNT(*) FROM tableCars) car_count,
    (SELECT COUNT(*) FROM tableBoats) boat_count,
    (SELECT COUNT(*) FROM tableTrees) tree_count

Answer 4

继Luc M的响应（提供单个列表）与具有单独值的列之后。你可以想象这可能是多么有用......

SELECT C.Accountnum as AccountNum, C.Address as Address, 'C' as Source 
From CustTable C 
Where C.AccountNum like '000%' 
Union All 
Select V.Accountnum as AccountNum, V.Name as Address, 'V' as Source 
from VendTable V 
Where V.AccountNum like 'A%'

Answer 5

SELECT *
FROM 
(
   SELECT 'Nb cars'  as description, COUNT(cars)  AS count_item FROM tableCars
   UNION ALL
   SELECT 'Nb boats' as description, COUNT(boats) AS count_item FROM tableBoats
   UNION ALL
   SELECT 'Nb tress' as description, COUNT(trees) AS count_item FROM tableTrees
) temp

SQL一个查询中的多个select count语句

5 个答案: