Microsoft SQL 是否可以连接两个 select 语句的结果

Question

我有一个包含以下信息的表格：客户、行、文本。 line 的值是 1-5，对应于一周中的几天，Mon-Fri。我们可能会看到如下数据：

|Customer | Line | Text | 
|123      | 1    | 018  |
|123      | 3    | 030  |
|234      | 2    | 129  |

周一和周三可以看到客户 123，周二可以看到客户 234。

我想为每个客户生成一行，如下所示：

123   Mon     Wed
234       Tue

我可以使用

select Customer, DaysOfWeek = 
case text
    when '' then '    '
    else 'Tue '         
end  
from routing where customer = %s and line = '2'

当 %s = '234' 时会生成“Tue”。

当我堆叠其中的五个，每个有一个由 UNION 分隔的行号 1 到 5 时，我会为客户 123 得到两个单独的行，分别是周一和周三。我无法将所有选择的结果放入语句放在一行上。我已经尝试过 CONCAT、&、+.... 我卡住了。

Answer 1

这应该可以在您的应用中使用：

如果它在您的应用程序中不能作为 CTE（通用表表达式）工作，那么我将转换为嵌套查询，这肯定可以工作。

    WITH CUSTOMERS AS 
  (SELECT DISTINCT Customer
    FROM routing),
  DAY1 AS 
(SELECT Customer,
        Line
  FROM routing
  WHERE Line = 1
  AND isnull(Text, '') <> ''),
  DAY2 AS 
(SELECT Customer,
        Line
  FROM routing
  WHERE Line = 2
  AND isnull(Text, '') <> ''),
  DAY3 AS 
(SELECT Customer,
        Line
  FROM routing
  WHERE Line = 3
  AND isnull(Text, '') <> ''),
  DAY4 AS 
(SELECT Customer,
        Line
  FROM routing
  WHERE Line = 4
  AND isnull(Text, '') <> ''),
  DAY5 AS 
(SELECT Customer,
        Line
  FROM routing
  WHERE Line = 5
  AND isnull(Text, '') <> '')
SELECT CUSTOMERS.Customer,
  CASE WHEN DAY1.Line IS NULL THEN '' ELSE 'Mon' END AS 'Mon',
  CASE WHEN DAY2.Line IS NULL THEN '' ELSE 'Tue' END AS 'Tue',
  CASE WHEN DAY3.Line IS NULL THEN '' ELSE 'Wed' END AS 'Wed',
  CASE WHEN DAY4.Line IS NULL THEN '' ELSE 'Thu' END AS 'Thu',
  CASE WHEN DAY5.Line IS NULL THEN '' ELSE 'Fri' END AS 'Fri'
  FROM CUSTOMERS
  LEFT JOIN DAY1
  ON CUSTOMERS.Customer = DAY1.Customer
  LEFT JOIN DAY2
  ON CUSTOMERS.Customer = DAY2.Customer
  LEFT JOIN DAY3
  ON CUSTOMERS.Customer = DAY3.Customer
  LEFT JOIN DAY4
  ON CUSTOMERS.Customer = DAY4.Customer
  LEFT JOIN DAY5
  ON CUSTOMERS.Customer = DAY5.Customer

好的，我继续创建嵌套查询版本。我非常有信心这将适用于您的应用程序。

    SELECT DISTINCT C.Customer,
  CASE WHEN DAY1.Line IS NULL THEN '' ELSE 'Mon' END AS 'Mon',
  CASE WHEN DAY2.Line IS NULL THEN '' ELSE 'Tue' END AS 'Tue',
  CASE WHEN DAY3.Line IS NULL THEN '' ELSE 'Wed' END AS 'Wed',
  CASE WHEN DAY4.Line IS NULL THEN '' ELSE 'Thu' END AS 'Thu',
  CASE WHEN DAY5.Line IS NULL THEN '' ELSE 'Fri' END AS 'Fri'
    FROM routing C
  LEFT JOIN (SELECT Customer,
        Line
  FROM routing
  WHERE Line = 1
  AND isnull(Text, '') <> '') DAY1
  ON C.Customer = DAY1.Customer
  LEFT JOIN (SELECT Customer,
        Line
  FROM routing
  WHERE Line = 2
  AND isnull(Text, '') <> '') DAY2
  ON C.Customer = DAY2.Customer
  LEFT JOIN (SELECT Customer,
        Line
  FROM routing
  WHERE Line = 3
  AND isnull(Text, '') <> '') DAY3
  ON C.Customer = DAY3.Customer
  LEFT JOIN (SELECT Customer,
        Line
  FROM routing
  WHERE Line = 4
  AND isnull(Text, '') <> '') DAY4
  ON C.Customer = DAY4.Customer
  LEFT JOIN (SELECT Customer,
        Line
  FROM routing
  WHERE Line = 5
  AND isnull(Text, '') <> '') DAY5
  ON C.Customer = DAY5.Customer

Answer 2

如果我猜对了，

select Customer, 
  Day1 = max(case line when '1' then 'Mon ' end),  
  Day2 = max(case line when '2' then 'Tue ' end),  
  --..       
from routing 
where customer = %s 
    and Len(text) > 0 -- skip empty text rows
group by Customer

此查询将为所需的一周中的每一天返回单行和单列。

Answer 3

有两种方法： 首先是 case 和 exists 函数，例如： 选择

case when exists (SELECT 1 FROM routing r1 WHERE r1.customer=r2.customer AND r1.Line=1) then 'Mon' else '   ' end ||
case when exists (SELECT 1 FROM routing r1 WHERE r1.customer=r2.customer AND r1.Line=2) then 'Tue' else '   ' end
[... next days...]
from routing r2 group by r2.customer

第二种方法更复杂，使用 PIVOT 选择，但并非所有数据库引擎都支持。