select和insert中的多个where子句

Question

所以我在数据库里面有2个表。第一个是名称映射的唯一ID

Customers
UID | CustomerName

在第二个表中，我有类似下面的内容

Orders
OrderNum | CustomerID | CustomerID2

现在我想插入订单，但我只有2个客户名称的名称，所以我想象下面的东西（不起作用）

insert into Orders select null, UID as id1, UID as id2 from Customers where CustomerName=="sven";

如何从第一张表中获取两个UID？

此外，我需要能够反过来并从表中选择

SELECT * FROM Orders a JOIN (Customers b) ON a.UID=b.UID WHERE b.CustomerName='sven'

这些都不起作用，我似乎无法在网上找到类似的东西。

Answer 1

更新：根据您的评论，如果您尝试将两个不同客户'ID插入一个订单，则可以执行

INSERT INTO Orders (CustomerID, CustomerID2)
SELECT c1.uid uid1, c2.uid uid2
  FROM
(
  SELECT uid 
    FROM customers
   WHERE customername = 'sven'
   LIMIT 1
) c1 CROSS JOIN
(
  SELECT uid 
    FROM customers
   WHERE customername = 'jhon'
   LIMIT 1
) c2

选择其中一个客户存在的订单

SELECT o.* 
  FROM orders o LEFT JOIN customers c1
    ON o.customerid = c1.uid LEFT JOIN customers c2
    ON o.customerid2 = c2.uid 
 WHERE c1.customername IN('sven', 'jhon')
    OR c2.customername IN('sven', 'jhon')

这是 SQLFiddle 演示

原始回答：您在寻找这个吗？

要插入

INSERT INTO Orders (CustomerID, CustomerID2)
SELECT c1.uid uid1, c2.uid uid2
  FROM customers c1 LEFT JOIN customers c2
    ON c1.customername = c2.customername
   AND c1.uid < c2.uid
 WHERE c1.customername = 'sven'
 LIMIT 1

选择

SELECT o.* 
  FROM orders o LEFT JOIN customers c1
    ON o.customerid = c1.uid LEFT JOIN customers c2
    ON o.customerid2 = c2.uid 
 WHERE c1.customername = 'sven'
    OR c2.customername = 'sven'

这是 SQLFiddle 演示

Answer 2

要从另一个表插入一个表，请使用this syntax：

INSERT [LOW_PRIORITY | HIGH_PRIORITY] [IGNORE]
    [INTO] tbl_name [(col_name,...)]
    SELECT ...
    [ ON DUPLICATE KEY UPDATE col_name=expr, ... ]

因此，在您的情况下，您的查询应该是：

INSERT INTO Orders (CustomerID, CustomerID2)
SELECT UID, UID
  FROM Customers WHERE CustomerName = 'sven';

如果您想从单个查询中插入多条记录，可以使用IN运算符代替=，如下所示：

INSERT INTO Orders (CustomerID, CustomerID2)
SELECT UID, UID
  FROM Customers WHERE CustomerName IN ('sven', 'smith');

您加入SELECT查询时出错：

在UID表格中没有UID的情况下，您使用Orders加入了两个表格。可能是你的意思CustomerID。试试这个：

SELECT * FROM Orders a 
  JOIN Customers b 
    ON a.CustomerID = b.UID 
 WHERE b.CustomerName='sven'

请参阅this SQLFiddle