Question

情况：

表1-#__ virtuemart_products

ggplot(data_small, aes(risk_datatheft_likelihood, risk_datatheft_damage)) + 
  geom_jitter(color="blue") + 
  labs(x = "damage", y = "likelihood",
       title = "Risk Map", subtitle = "Datatheft") + 
        theme_classic() +
        theme(legend.position="bottom") + 
        geom_hline(yintercept = 0.5, color="red") + 
        geom_hline(yintercept = 1.5) + 
        geom_hline(yintercept = 2.5) + 
        geom_hline(yintercept = 3.5) + 
        geom_hline(yintercept = 4.5) + 
        geom_vline(xintercept = 0.5, color="red") + 
        geom_vline(xintercept = 1.5) + 
        geom_vline(xintercept = 2.5) + 
        geom_vline(xintercept = 3.5) + 
        geom_vline(xintercept = 4.5)

data_big.csv
risk_datatheft_likelihood;risk_datatheft_damage
B;3
B;2
C;4
A;1
D;5

data_small.csv
risk_datatheft_likelihood;risk_datatheft_damage
C;4
A;2
B;3
C;4
D;1

表2-#__ virtuemart_product_badges

virtuemart_product_id | product_special
PRODUCTS_IDS | 0 or 1

我有一个默认的SQL

virtuemart_product_id | product_badge
PRODUCTS_IDS | for this situation code 3

结果是产品ID，例如2,3,225，...

我需要修改此SQL语法，以便从2个不同的表中选择ID，并返回一列。

如果我这样修改语法：

SELECT p.`virtuemart_product_id`
FROM `#__virtuemart_products` as p
WHERE p.`product_special` = 1;

结果是：

SELECT p.`virtuemart_product_id`, badges_table.`virtuemart_product_id`
FROM `#__virtuemart_products` as p, `#__virtuemart_product_badges` as badges_table
WHERE p.`product_special` = 1 OR badges_table.`badge` = 3

为什么第一列1,1,1，...？这里必须是product_id，没有product_special代码
我需要将此结果分组到一个字段tentmart_product_id

我做错了什么？

Answer 1

我认为您正在寻找的是从两个不同表中获取的ID的UNION。

    SELECT p.`virtuemart_product_id`, badges_table.`virtuemart_product_id`
    FROM `#__virtuemart_products` as p, `#__virtuemart_product_badges` as 
    badges_table
    WHERE p.`product_special` = 1 OR badges_table.`badge` = 3

上面的查询在做什么，它正在两个表之间执行联接，条件是product_special应该为1或badge应该为3。因此，一个表的每一行将与另一表的每一行联接条件将满足的表。

要从两个表中获取ID，可以根据条件从每个表中获取结果，然后对它们执行UNION。例如

     (SELECT `virtuemart_product_id` FROM `#__virtuemart_products` WHERE 
     `product_special` = 1) 
      UNION 
     (SELECT `virtuemart_product_id` FROM 
     `#__virtuemart_product_badges` WHERE `badge` = 3)

我希望这会有所帮助。

MySQL-从2个不同的表和组结果中选择product_id

1 个答案: