Question

我有一个交易表和一个标签表。我想得到按标签分组的事务表中所有事务的总和。有两种不同类型的交易：“预算”和“实际”

此查询将返回我想要的“预算”交易：

  SELECT tg.name as tag, SUM(amount) as budgetTotal 
    FROM transaction tx
    JOIN transaction_tag tt ON tt.transaction_id = tx.id
    JOIN tag tg ON tg.id = tt.tag_id
   WHERE tx.type = "budget"
     AND tx.date >= '2011-07-15' 
     AND tx.date < '2011-08-15'
GROUP BY tg.name

当然，“实际”交易的查询几乎相同：

  SELECT tg.name as tag, SUM(amount) as actualTotal 
    FROM transaction tx
    JOIN transaction_tag tt ON tt.transaction_id = tx.id
    JOIN tag tg ON tg.id = tt.tag_id
   WHERE tx.type = "actual"
     AND tx.date >= '2011-07-15' 
     AND tx.date < '2011-08-15'
GROUP BY tg.name

我的问题：如何将这两个查询的结果分组为一个，所以我得到一个包含三列的结果表：tag，budgetTotal和actualTotal？

Answer 1

试试这个：

  SELECT tg.name, 
         CASE WHEN tx.type = "actual" THEN SUM(amount) END AS actualTotal,
         CASE WHEN tx.type = "budget" THEN SUM(amount) END AS budgetTotal
  FROM....
  WHERE  tx.type IN ("actual", "budget")
  AND   ....
  GROUP BY tg.name

Answer 2

SELECT tg.name as tag, SUM(amount) as budgetTotal, 'budget' as rectype
FROM transaction tx
JOIN transaction_tag tt ON tt.transaction_id = tx.id
JOIN tag tg ON tg.id = tt.tag_id
WHERE tx.type = "budget"
AND tx.date >= '2011-07-15' 
AND tx.date < '2011-08-15'
GROUP BY tg.name

UNION ALL

SELECT tg.name as tag, SUM(amount) as actualTotal, , 'actual' as rectype
FROM transaction tx
JOIN transaction_tag tt ON tt.transaction_id = tx.id
JOIN tag tg ON tg.id = tt.tag_id
WHERE tx.type = "actual"
AND tx.date >= '2011-07-15' 
AND tx.date < '2011-08-15'
GROUP BY tg.name

Answer 3

不要忽略其他答案（这可能更好），但如果适合的话，这里是如何将它作为两个单独的行。此外，这个答案可以扩展到任意数量的tx.type而不更改查询（如果你删除了当然在where子句中对t.type的引用）：

SELECT tg.name as tag, tx.type, SUM(amount) as total
    FROM transaction tx
    JOIN transaction_tag tt ON tt.transaction_id = tx.id
    JOIN tag tg ON tg.id = tt.tag_id
   WHERE tx.date >= '2011-07-15' 
     AND tx.date < '2011-08-15'
     AND tx.type in ("budget", "actual")
GROUP BY tg.name, tx.type;

组合由同一列分组的两个GROUP BY查询

3 个答案: