Question

我有两张桌子。我想根据某些条件离开其中一个表。我想做这样的事情：

IF (Projects.paymentType==1)
    LEFT JOIN ProjectBudgetFixedPrice ON (Projects.budget=ProjectBudgetFixedPrice.id)
ELSE
    LEFT JOIN ProjectBudgetPerHourPrice ON (Projects.budget=ProjectBudgetPerHourPrice.id)

我创建了以下内容，但它无效。

SELECT * FROM Projects LEFT JOIN
(IF (Projects.paymentType==1,ProjectBudgetFixedPrice,ProjectBudgetPerHourPrice))
    ON 
(IF (Projects.paymentType==1,Projects.budget=ProjectBudgetFixedPrice.id,Projects.budget=ProjectBudgetFixedPrice.id))

WHERE (Projects.statusCode=3 OR Projects.statusCode=4) AND Projects.suspended='N' AND (Projects.paymentType=1 OR Projects.paymentType=2)

请提供任何帮助或建议？

Answer 1

您应该可以使用UNION。

像

这样的东西

SELECT
  *
FROM
  Projects
  LEFT JOIN
    ProjectBudgetFixedPrice
    ON Projects.budget = ProjectBudgetFixedPrice.id
WHERE
  Projects.paymentType = 1
  AND ((Projects.statusCode = 3 OR Projects.statusCode = 4)
  AND Projects.suspended = 'N'
  AND (Projects.paymentType = 1 OR Projects.paymentType = 2))
UNION
SELECT
  *
FROM
  Projects
  LEFT JOIN
    ProjectBudgetPerHourPrice
    ON Projects.budget = ProjectBudgetPerHourPrice.id
WHERE
  Projects.paymentType <> 1
  AND ((Projects.statusCode = 3 OR Projects.statusCode = 4)
  AND Projects.suspended = 'N'
  AND (Projects.paymentType = 1 OR Projects.paymentType = 2));

HTH

决定基于CONDITION对哪个表进行LEFT JOIN

1 个答案: