SQL- 过滤器的多个子句

Question

所以我不完全确定它应该是 WHERE 语句还是子句，还是 CASE。坦白说，我还在努力学习subclause和CASE的用例。

最后我想要的是他们的出席人数以及他们在特定时间范围内支付的发票总额。

我在尝试“错误：位于或接近“来自”位置的语法错误：349”时遇到错误

预期输出：Child姓名、中心 ID、班级名称、出勤人数、发票总和、日期，

我要加入多个表格，想过滤特定日期内的出勤率和特定日期内支付的发票：

select accounts.fname as first_name, accounts.lname as last_name, accounts.dob, centers.label, classrooms.label as classroom_label, 
count(*) as no_of_days_attended, sum(transactions.amount / 100.0) as sum_of_transactions_paid, 
from daily_reports
join account_classrooms
on daily_reports.account_classroom_id = account_classrooms.id
join accounts
on account_classrooms.account_id = accounts.id
join classrooms
on account_classrooms.classroom_id = classrooms.id
join centers
on classrooms.center_id = centers.id
join invoices
on centers.id = invoices.center_id
join transactions
on transactions.invoice_id = invoices.id
where daily_reports.ref_date and transactions.created_at > {{start_date}} and daily_reports.ref_date and transactions.created_at < {{end_date}} and centers.id = {{center_id}}
group by daily_reports.account_classroom_id, accounts.id, classrooms.id, centers.id,

非常感谢！

Answer 1

您遇到了几个问题。

首先，在 FROM 子句之前多了一个逗号，在 GROUP BY 的末尾多了一个逗号。您的 GROUP BY 列不会出现在您的 SELECT 语句中，因此这是行不通的。在进行聚合（SUM()、MAX() 等）时，引擎必须知道根据哪些列对聚合进行分组。这些是您的 SELECT 列表中的列。

其次，您不能像这样同时计算两列：

daily_reports.ref_date and transactions.created_at > {{start_date}}

如果你这样做，你会得到这个错误：

An expression of non-boolean type specified in a context where a condition is expected, near 'AND'.

每个评估都必须是原子的。在这个例子中，它必须是这样的：

daily_reports.ref_date > {{start_date}} and transactions.created_at > {{start_date}}

但是，可以使用 BETWEEN 运算符进一步清理 WHERE 子句。此外，最好不要使用隐式 JOIN。在您的代码中定义 JOIN 的类型（例如 INNER JOIN）。

我已应用别名、格式化代码并应用 BETWEEN 运算符。看看这是否适合你。如您所见，代码格式正确时，可读性更强，也更容易发现问题。

SELECT  a.fname AS first_name
        ,a.lname AS last_name
        ,a.dob
        ,cn.label
        ,cl.label AS classroom_label
        ,COUNT(*) AS no_of_days_attended
        ,SUM(t.amount / 100.0) AS sum_of_transactions_paid
FROM    daily_reports AS dr
        INNER JOIN account_classrooms AS ac ON dr.account_classroom_id = ac.id
        INNER JOIN accounts AS a ON ac.account_id = a.id
        INNER JOIN classrooms AS cl ON ac.classroom_id = cl.id
        INNER JOIN centers AS cn ON cl.center_id = cn.id
        INNER JOIN invoices AS i ON cn.id = i.center_id
        INNER JOIN transactions AS t ON t.invoice_id = i.invoices.id
WHERE   dr.ref_date BETWEEN @start_date AND @end_date
        AND t.created_at BETWEEN @start_date AND @end_date
        AND cn.id = @center_id
GROUP BY
        a.fname
        ,a.lname
        ,a.dob
        ,cn.label

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