MySQL 合并两个 SELECT CASE 查询 Table

Question

我想将两个查询合并为一个完整的查询。我需要将两个查询分组到一个聚合字段 (MFG) 上。我会假设你使用 JOIN 但它在同一个 table 上并且带有 CASE 所以我不确定它是如何工作的。

第一次查询 (2015)

SELECT 
    CASE
        WHEN ITEM LIKE '%1%' THEN 'MFG1'
        WHEN ITEM LIKE '%2%' THEN 'MFG2'
        WHEN ITEM LIKE '%3%' THEN 'MFG3'
        ELSE ''
    END AS MFG,
    SUM(COST) AS Cost2015
FROM
    table
WHERE
    TRANS_DATE BETWEEN '2015-12-01' AND '2015-12-31'
GROUP BY MFG

第二次查询 (2014)

SELECT 
    CASE
        WHEN ITEM LIKE '%1%' THEN 'MFG1'
        WHEN ITEM LIKE '%2%' THEN 'MFG2'
        WHEN ITEM LIKE '%3%' THEN 'MFG3'
        ELSE ''
    END AS MFG,
    SUM(COST) AS Cost2014
FROM
    table
WHERE
    TRANS_DATE BETWEEN '2014-12-01' AND '2014-12-31'
GROUP BY MFG

期望的结果

MFG  |  Cost2015  |  Cost2014
MFG1 |   1500     |     0
MFG2 |   1000     |    1200
MFG3 |     0      |    3600
     |    100     |     15

Answer 1

您可以在 SUM()

中使用 CASE

SELECT 
    CASE
        WHEN ITEM LIKE '%1%' THEN 'MFG1'
        WHEN ITEM LIKE '%2%' THEN 'MFG2'
        WHEN ITEM LIKE '%3%' THEN 'MFG3'
        ELSE ''
    END AS MFG,
    SUM(CASE WHEN TRANS_DATE BETWEEN '2014-12-01' AND '2014-12-31' THEN COST ELSE 0 END) AS Cost2014,
    SUM(CASE WHEN TRANS_DATE BETWEEN '2015-12-01' AND '2015-12-31' THEN COST ELSE 0 END) AS Cost2015
FROM
    TABLE
WHERE
    TRANS_DATE BETWEEN '2014-12-01' AND '2015-12-31'
GROUP BY MFG

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