无法分隔 MySQL 查询中的不同 ID

Question

Write a SELECT statement that returns one row for each vendor in the Invoices table that contains these columns: The vendor_id column from the Vendors table The sum of the invoice_total columns in the Invoices table for that vendor

SELECT 
    distinct vendor_id, SUM(invoice_total) AS Invoice_totals
FROM
    invoices i
    join vendors v using (vendor_id);

我可以在没有 SUM(invoice_total) 的情况下显示所有 34 个 vendor_ids，但是一旦我添加它，它就会将它们合并为一个。我怎样才能避免这种情况发生？

Answer 1

不要将 select distinct 与 sum() 一起使用。使用 group by。这使得查询的意图更加清晰。

其次，你想要一个left join:

SELECT vendor_id, SUM(i.invoice_total) AS Invoice_totals
FROM vendors v LEFT JOIN
     invoices i
     using (vendor_id)
GROUP BY vendor_id;

无法分隔 MySQL 查询中的不同 ID

Cannot separate the distinct ids in MySQL query

sql

summary

distinct