试图在MySQL中的单个查询中选择多个计数

我有一张商店订单表。这些订单具有一个布尔属性，该属性说明它们是否需要交付给客户。还有一个表格说明订单是否完整

我想计算已交付发票的数量、剩余发票的数量，然后计算已完成付款的发票总数

这就是我迄今为止所做的尝试：

SELECT 
    COUNT(SELECT INVOICE_ID FROM INVOICE_LINE AS I, INVOICE_COMPLETE AS IC WHERE TO_DELIVER = 1 AND I.INVOICE_ID = IC.INVOICE_ID AND IC.COMPLETE = 1) AS DELIVERED, 
    COUNT(SELECT INVOICE_ID FROM INVOICE_LINE AS I, INVOICE_COMPLETE AS IC WHERE TO_DELIVER = 0 AND I.INVOICE_ID = IC.INVOICE_ID AND IC.COMPLETE = 1) AS REMAINING,
    COUNT(INVOICE_ID) AS TOTAL
FROM INVOICE_LINE AS I, INVOICE_COMPLETE AS IC
WHERE TO_DELIVER = 1
AND I.INVOICE_ID = IC.INVOICE_ID

这会引发以下语法错误：

#1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'SELECT INVOICE_ID FROM INVOICE_LINE AS I, INVOICE_COMPLETE AS IC WHERE TO_DELIVE' at line 2

---

我哪里出了问题。这是我第一次尝试这样嵌套语句。

有一种更简单的方法：外部连接发票\u完成并计数匹配项：

SELECT 
  COUNT(IC.INVOICE_ID) AS DELIVERED, 
  COUNT(*) - COUNT(IC.INVOICE_ID) AS REMAINING,
  COUNT(*) AS TOTAL
FROM INVOICE_LINE AS I
LEFT JOIN INVOICE_COMPLETE AS IC ON I.INVOICE_ID = IC.INVOICE_ID AND IC.COMPLETE = 1
WHERE TO_DELIVER = 1;

编辑：嗯，我还应该解释一下你做错了什么：Count需要*、一列或一个表达式。对于列或表达式，它将统计非空出现次数，对于*它统计记录。您可以使用select语句作为表达式，但它必须有额外的括号，并且必须包含from子句：select COUNT select x from y from

---

最后一个建议是：使用显式连接语法INNER join x ON…，LEFT join y ON…，等等，而不是只列出带有逗号的表。这增强了可读性并有助于避免错误。

您可以按如下方式编写：

declare @toDeliver as int = (SELECT COUNT(INVOICE_ID) FROM INVOICE_LINE AS I, INVOICE_COMPLETE      AS IC WHERE TO_DELIVER = 0 AND I.INVOICE_ID = IC.INVOICE_ID AND IC.COMPLETE = 1)
declare @deliverd as int = (SELECT COUNT(INVOICE_ID) FROM INVOICE_LINE AS I, INVOICE_COMPLETE AS    IC WHERE TO_DELIVER = 1 AND I.INVOICE_ID = IC.INVOICE_ID AND IC.COMPLETE = 1) 
SELECT 
    @toDeliver as REMAINING, 
    @delivered as DELIVERED,
    @toDeliver + @delivered AS TOTAL

---

其他答案为您提供了更好的方法

但是错误似乎来自count函数内部的subselect

此更改可能适用于您：

    SELECT 
    (SELECT COUNT(INVOICE_ID) FROM INVOICE_LINE AS I, INVOICE_COMPLETE AS IC WHERE TO_DELIVER = 1 AND I.INVOICE_ID = IC.INVOICE_ID AND IC.COMPLETE = 1) AS DELIVERED, 
    (SELECT COUNT(INVOICE_ID) FROM INVOICE_LINE AS I, INVOICE_COMPLETE AS IC WHERE TO_DELIVER = 0 AND I.INVOICE_ID = IC.INVOICE_ID AND IC.COMPLETE = 1) AS REMAINING,
    COUNT(INVOICE_ID) AS TOTAL
FROM INVOICE_LINE AS I, INVOICE_COMPLETE AS IC
WHERE TO_DELIVER = 1
AND I.INVOICE_ID = IC.INVOICE_ID

这只是将计数移动到子选择中

或在子选项周围添加括号：

SELECT 
    COUNT((SELECT INVOICE_ID FROM INVOICE_LINE AS I, INVOICE_COMPLETE AS IC WHERE TO_DELIVER = 1 AND I.INVOICE_ID = IC.INVOICE_ID AND IC.COMPLETE = 1)) AS DELIVERED, 
    COUNT((SELECT INVOICE_ID FROM INVOICE_LINE AS I, INVOICE_COMPLETE AS IC WHERE TO_DELIVER = 0 AND I.INVOICE_ID = IC.INVOICE_ID AND IC.COMPLETE = 1)) AS REMAINING,
    COUNT(INVOICE_ID) AS TOTAL
FROM INVOICE_LINE AS I, INVOICE_COMPLETE AS IC
WHERE TO_DELIVER = 1
AND I.INVOICE_ID = IC.INVOICE_ID
;

---

你能解释一下左连接发生了什么吗？是的。从A.x=B.y的左侧连接B中选择*。如果存在与A.x匹配的连接，则与正常连接一样。但是，如果A.x没有匹配项，则A记录与空B记录连接。例如，B字段为空，B.y为空。我只是注意到我的select语句不正确。我过去和现在都对id.complete和to_deliver感到困惑。交付属于表发票行吗？你算什么：交付，完成=>1,1=交付，0,1=剩余，*，*=总计？还是1，*=总数？或*，1=总数？