php - 连接 2 列以创建帐户流查询

Question

我有两张表，一张用于客户信用(付款)，它看起来像这样:

id     client     date              amount
1       ana       2012-01-01        5000  
2       ana       2012 02-01        10000
3       ana       2012-03-01        5000

等等..

还有另一个借方(提款)表，如下所示:

id    client      date             amount 
1       ana       2012-01-15        5000
2       ana       2012 02-15        8000
3       ana       2012-03-15        9000

等等...

我想生成一个查询，按日期对每个客户的所有交易进行排序，将 2 个日期列合并为一个，然后按日期排序，它应该如下所示:

date           payment     withdrawal 
2012-01-01     5000           ----
2012-01-15     -----          5000
2012-02-01     10000          ----  
2012-02-15     -----          8000
2012-03-01      5000          ----
2012-03-15     -----          9000

这是我尝试过的，但我知道它是错误的，并且它给出了重复的记录:

SELECT payments.amount, payments.date withdrawals.amount, withdrawals.date
FROM payments,withdrawals 
WHERE payments.client = withdrawals.client
ORDER BY date

我尝试了 LEFT JOIN 但它给出了相同的结果:

 SELECT payments.amount, payments.date, withdrawals.amount, withdrawals.date
 FROM payments 
 LEFT JOIN withdrawals 
 ON payments.client= withdrawals.client
 ORDER BY date

请帮忙，谢谢

Answer 1

您需要执行两个简单的 SELECT 查询，每个表分别执行一个查询，然后使用 UNION 关键字组合结果，如下所示:

SELECT date, amount AS payment, NULL AS withdrawal FROM payments WHERE client = 'ana'
UNION ALL
SELECT date, NULL AS payment, amount AS withdrawal FROM withdrawals WHERE client = 'ana'
ORDER BY date

您不想进行任何类型的联接，因为每一行的数据仅从一个表中提取，而不是从另一个表中提取。