Question

我正在编写一个MySQL查询，该查询获取潜在客户列表（提交表单中的潜在客户）和该订单的乘客数量，其中潜在客户详细信息缺失或为空或= default。所以我加入了lead_detail表，但只知道如何检查它是否存在，而不是它是否存在。这是我到目前为止 -

SELECT l1.id, (
    /* sub query to get the passenger count from field 22 */ 
    SELECT lm1.`value` FROM lead_detail lm1
    WHERE lm1.form_id = l1.form_id AND lm1.lead_id = l1.id
    AND lm1.field_number = 22
) passengers FROM lead l1

/* join our detail table */
LEFT JOIN lead_detail lm2 ON (l1.id = lm2.lead_id)
WHERE lm2.field_number = 29 AND lm2.form_id = 1
AND lm2.lead_id = l1.id AND (lm2.`value` = 'default' OR lm2.`value` = '')

/* make sure we are on lead form 1 and they have paid */
AND l1.form_id = 1 AND l1.payment_status = 'Paid'

仅作为参考，字段编号 22 =乘客数量

字段编号 29 =表单访问密钥（空，default或不存在）

值得注意的是，这是Gravity Forms WordPress插件，但这绝对是我想要实现的自定义操作。下面的lm2表结构 -

(int) id
(int) lead_id
(int) form_id
(int) field_number
(string) value

希望很清楚我想要做什么。谢谢！

Answer 1

您应该更改lead_detail子查询的别名，让我们说lm2，或者更改主查询中同一个表的别名。例如：

/* sub query to get the passenger count from field 22 */ 
    SELECT lm2.`value` FROM lead_detail lm2
    WHERE lm2.form_id = l.form_id AND lm2.lead_id = l.id
    AND lm2.field_number = 22

MySQL加入NOT EXISTS或='default'或=''

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