MYSQL 有报表和计算问题

Question

这个 mySQL 语句有什么问题？

我检查 C_BATCH_ID 在 batch table 然后将其与从引用中提取的值进行比较 (C_KEY)

它 returns 什么都没有，如果我将 MAX( C_BATCH_ID ) 替换为 23它returnsn条记录.

SELECT
    contract.KEY AS C_KEY,
    contract.BATCH_ID AS C_BATCH_ID,
    contract.CUSTOMER_NAME as C_NAME,
    batch.BATCH_ID = B_BATCH_ID
FROM
    contract
INNER JOIN 
    batch ON contract.BATCH_ID = batch.BATCH_ID 
HAVING
    SUBSTRING_INDEX( C_KEY, '-', 1 ) = MAX( B_BATCH_ID )
ORDER BY
    contract.CUSTOMER_NAME

感谢您的帮助。 :)

合同table

id	C_KEY	C_BATCH_ID	C_NAME
1	10-KEY01	10	Customer 1
2	23-KEY01	23	Customer 2
3	23-KEY02	23	Customer 3
4	12-KEY01	12	Customer 2
5	23-KEY03	23	Customer 4

批量table

B_BATCH_ID	BATCH_NAME
1	Batch 1
2	Batch 2
3	Batch 3
4	Batch 4
10	Batch 10
12	Batch 12
23	Batch 23

期望的结果，因为 23 是 B_BATCH_ID 的最大值：

id	C_KEY	C_BATCH_ID	C_NAME	B_BATCH_ID
2	23-KEY01	23	Customer 2	23
3	23-KEY02	23	Customer 3	23
5	23-KEY03	23	Customer 4	23

Answer 1

您需要在子查询中获取 MAX(BATCH_ID)。解决方案可能是这样的：

SELECT
    contract.KEY AS C_KEY,
    contract.BATCH_ID AS C_BATCH_ID,
    contract.CUSTOMER_NAME as C_NAME
FROM
    contract
WHERE
    SUBSTRING_INDEX( contract.KEY, '-', 1 ) = (SELECT MAX(BATCH_ID) FROM batch)
ORDER BY
    contract.CUSTOMER_NAME

基于示例数据 contract.BATCH_ID 可以用来代替 SUBSTRING_INDEX( contract.KEY, '-', 1 ) 但不确定在实际数据中是否有这样做的原因

MYSQL 有报表和计算问题

MYSQL HAVING STATEMENT AND CALCULATION ISSUE

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