Question

我在一个查询中执行多个选择时遇到问题。这就是我的工作：

SELECT 1 AS VisitsToday, `Datum Bezoek 1` FROM `psttodo-uit` WHERE CAST(`Datum Bezoek 1` AS DATE) = CURRENT_DATE AND PB = 1
UNION
SELECT 2 AS ConversationsToday, `Datum Bezoek 1` FROM `psttodo-uit` WHERE CAST(`Datum Bezoek 1` AS DATE) = CURRENT_DATE AND PG = 1
UNION
SELECT 3 AS PermitsToday, `Datum Bezoek 1` FROM `psttodo-uit` WHERE CAST(`Datum Bezoek 1` AS DATE) = CURRENT_DATE AND PA = 1;

但我得到了这个结果：

array (size=15)
      0 => 
        array (size=2)
          'VisitsToday' => string '1' (length=1)
          'Datum Bezoek 1' => string '2014-02-28 08:25:34' (length=19)
      1 => 
        array (size=2)
          'VisitsToday' => string '1' (length=1)
          'Datum Bezoek 1' => string '2014-02-28 08:55:34' (length=19)
      2 => 
        array (size=2)
          'VisitsToday' => string '1' (length=1)
          'Datum Bezoek 1' => string '2014-02-28 12:22:34' (length=19)
      3 => 
        array (size=2)
          'VisitsToday' => string '1' (length=1)
          'Datum Bezoek 1' => string '2014-02-28 12:28:34' (length=19)
      4 => 
        array (size=2)
          'VisitsToday' => string '1' (length=1)
          'Datum Bezoek 1' => string '2014-02-28 16:13:34' (length=19)
      5 => 
        array (size=2)
          'VisitsToday' => string '2' (length=1)
          'Datum Bezoek 1' => string '2014-02-28 08:25:34' (length=19)
      6 => 
        array (size=2)
          'VisitsToday' => string '2' (length=1)
          'Datum Bezoek 1' => string '2014-02-28 08:55:34' (length=19)
      7 => 
        array (size=2)
          'VisitsToday' => string '2' (length=1)
          'Datum Bezoek 1' => string '2014-02-28 12:22:34' (length=19)
      8 => 
        array (size=2)
          'VisitsToday' => string '2' (length=1)
          'Datum Bezoek 1' => string '2014-02-28 12:28:34' (length=19)
      9 => 
        array (size=2)
          'VisitsToday' => string '2' (length=1)
          'Datum Bezoek 1' => string '2014-02-28 16:13:34' (length=19)
      10 => 
        array (size=2)
          'VisitsToday' => string '3' (length=1)
          'Datum Bezoek 1' => string '2014-02-28 08:25:34' (length=19)
      11 => 
        array (size=2)
          'VisitsToday' => string '3' (length=1)
          'Datum Bezoek 1' => string '2014-02-28 08:55:34' (length=19)
      12 => 
        array (size=2)
          'VisitsToday' => string '3' (length=1)
          'Datum Bezoek 1' => string '2014-02-28 12:22:34' (length=19)
      13 => 
        array (size=2)
          'VisitsToday' => string '3' (length=1)
          'Datum Bezoek 1' => string '2014-02-28 12:28:34' (length=19)
      14 => 
        array (size=2)
          'VisitsToday' => string '3' (length=1)
          'Datum Bezoek 1' => string '2014-02-28 16:13:34' (length=19)

我也尝试了以下内容：

SELECT `Datum Bezoek 1` AS VisitsToday FROM `psttodo-uit` WHERE CAST(`Datum Bezoek 1` AS DATE) = CURRENT_DATE AND PB = 1
UNION
SELECT `Datum Bezoek 1` AS ConversationsToday FROM `psttodo-uit` WHERE CAST(`Datum Bezoek 1` AS DATE) = CURRENT_DATE AND PG = 1
UNION
SELECT `Datum Bezoek 1` AS PermitsToday FROM `psttodo-uit` WHERE CAST(`Datum Bezoek 1` AS DATE) = CURRENT_DATE AND PA = 1

但后来我得到了这个结果：

array (size=5)
   0 => 
     array (size=1)
       'VisitsToday' => string '2014-02-28 08:25:34' (length=19)
   1 => 
     array (size=1)
       'VisitsToday' => string '2014-02-28 08:55:34' (length=19)
   2 => 
     array (size=1)
       'VisitsToday' => string '2014-02-28 12:22:34' (length=19)
   3 => 
     array (size=1)
       'VisitsToday' => string '2014-02-28 12:28:34' (length=19)
   4 => 
     array (size=1)
       'VisitsToday' => string '2014-02-28 16:13:34' (length=19)

我试图得到的是一个包含3个键“VisitsToday”，“ConversationsToday”和“PermitsToday”的数组，每个键都包含一个从数据库中选择日期的数组。

更新
使用不同列的解决方法如下：

SELECT 1 AS VisitsToday, NULL AS ConversationsToday, NULL AS PermitsToday
FROM `psttodo-uit` WHERE CAST(`Datum Bezoek 1` AS DATE) = CURRENT_DATE AND PB = 1)
UNION
SELECT NULL, 2 AS ConversationsToday, NULL
FROM `psttodo-uit` WHERE CAST(`Datum Bezoek 1` AS DATE) = CURRENT_DATE AND PG = 1)
UNION
SELECT NULL, NULL, 3 AS PermitsToday
FROM `psttodo-uit` WHERE CAST(`Datum Bezoek 1` AS DATE) = CURRENT_DATE AND PA = 1)

但后来我收到这样的错误：

Syntax error or access violation: 1064 You have an error in your SQL syntax; check the    manual that corresponds to your MySQL server version for the right syntax to use near ')
UNION SELECT NULL, 2 AS ConversationsToday, NU' at line 2

Answer 1

您试图为一列提供多个名称 - 这根本无法完成。使用union时，将在第一个选择中分配列名 More info on UNION

可能的解决方法是添加不同的列，因此它看起来像这样：

SELECT 1 AS VisitsToday, NULL AS ConversationsToday, NULL AS PermitsToday, ...
  FROM ...
UNION
SELECT NULL            , 2                         , NULL                , ...
  FROM ...
...
UNION
SELECT NULL            , NULL                      , 3                   , ...
  FROM ...
 ..;

一个查询中有多个SELECT

1 个答案: