Question

可以在一个查询中执行双重选择语句，并使用sum和suma分别显示每个值，以便第一个选择我只期望一个值，并且对于第二个4值。

echo ' ' . htmlentities($rowsm['sum'], ENT_QUOTES, 'UTF-8') . '<br>'; 
$query = "SELECT SUM(a.totalpoints) as sum
          FROM total as a
          WHERE a.id = '$id'
          GROUP BY a.id
          UNION ALL

SELECT SUM(s.points) as suma
       FROM points as s 
       GROUP BY s.id

这是我得到的输出

A 21 first select
A 11 second select
A 10 second select
A 9 second select
A 14 second select

21总和

A 11 points
A 10 points
A 9 points
A 14 points

Answer 1

在UNION ALL中，相应的字段需要具有相同的名称，否则系统将如何决定在列标题中显示哪个名称？您的SQL必须采用以下形式：

SELECT SUM(a.totalpoints) as suma
      FROM total as a
      WHERE a.id = '$id'
      GROUP BY a.id
      UNION ALL

SELECT SUM(s.points) as suma
   FROM points as s 
   GROUP BY s.id

此外，sum是一个关键字，因此您不能使用名为sum的别名。即“作为总和”可能无效。

Answer 2

除非是一个事务，否则不能在一个查询中调用多个select语句。将您的查询更改为：

$query = "
    START TRANSACTION;
    SELECT SUM(a.totalpoints) as suma
              FROM total as a
              WHERE a.id = '$id'
              GROUP BY a.id
              UNION ALL

    SELECT SUM(s.points) as suma
           FROM points as s 
           GROUP BY s.id
    COMMIT;";

同样@Swagata提到你不能使用关键字作为别名

如何在一个查询SQL中执行双精度语句

2 个答案: