Question

我有一个查询，我按照自己的意愿开始工作有点麻烦，查询看起来像这样：

SELECT
  hf.file_path AS image,
  hop.order_product_name AS product,
  hop.order_product_price AS unit_flat_price,
  .... <SHORTENED DOWN QUERY> ....
  hc.currency_symbol AS currency,
  ho.order_payment_method AS payment_method,
  ho.order_created AS created
FROM
  shop_order AS ho
LEFT JOIN
  shop_order_product AS hop ON ho.order_id = hop.order_id
LEFT JOIN
  shop_product AS hp ON hop.product_id = hp.product_id
LEFT JOIN
  shop_file AS hf ON(
    IF(
      hp.product_parent_id > 0,
      hp.product_parent_id,
      hp.product_id
    )
  ) = hf.file_ref_id
LEFT JOIN
  shop_currency AS hc ON ho.order_currency_id = hc.currency_id
WHERE
  ho.order_id = X AND(
    hf.file_ordering = 0 OR hf.file_ordering = NULL
  )

现在我的问题是，有时shop_file表在shop_file表中没有匹配，然后我需要查询＆＃34;忽略＆＃34;加入，但是如果匹配，那么我需要它来应用AND条款中的WHERE部分我已经尝试了

WHERE
  ho.order_id = X (
    IF(
      hf.file_path = NULL, 
      '',
      AND(
        hf.file_ordering = 0 OR hf.file_ordering = NULL
      )
    )
  )

我尝试使用hf.file_path =行的不同值，但没有任何帮助，我仍然遇到语法错误#1064 - You have an error in your .... syntax to use near '( IF(

我也试过

WHERE
  ho.order_id = X AND(
    hf.file_id = NULL OR(
      hf.file_ordering = 0 OR hf.file_ordering = NULL
    )
  )

但这只是返回一个空的结果集（如果我删除整个AND( ... )部分，我会得到我想要的结果。

现在我知道我可以按照

的方式做点什么

WHERE
  ho.order_id = X AND(
    IF EXIST(SELECT file_path FROM ... )

但是这需要我在该查询中添加其他JOINS以获得正确的结果（如果有图像）并且我想尝试避免必须添加JOIN＆＃39}如果可能WHERE ... AND( IF_EXIST (SELECT。

Answer 1

您需要将CASE添加到where语句中。

尝试这一点，将其添加到WHERE子句中：

AND CASE
WHEN hf.file_path IS NOT NULL
THEN hf.file_ordering = 0 OR hf.file_ordering IS NULL END;

具有IF条件的Where子句

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