我需要一個查詢，該查詢將獲取具有4種不同條件的sum（column），其中條件按條件分組

Question

這是我的查詢：

SELECT
    date,
    (SELECT sum(sessions) as org FROM datatwo WHERE medium='Organic Search' GROUP by date),
    (SELECT sum(sessions) as soc FROM datatwo WHERE medium='Social' GROUP BY date),
    (SELECT sum(sessions) as dir FROM datatwo WHERE medium='Direct' group by date),
    (SELECT sum(sessions) as ref FROM datatwo WHERE medium='Referral')
FROM datatwo
GROUP BY date

我試圖在一個查詢中組合4個查詢，但出現此錯誤，我正在使用mysql DB。

1242-子查詢返回多於1行

Answer 1

當您將查詢結果用作列時，它必須恰好返回一行和一列。 像這樣的表達式：

(SELECT sum(sessions) as org FROM datatwo WHERE medium='Organic Search' GROUP by date)

將為每個不同的date值返回一行。

我懷疑你想要這個：

SELECT
    date,
    sum(case when medium='Organic Search' then sessions end) as org,
    sum(case when medium='Social' then sessions end) as soc,
    sum(case when medium='Direct' then sessions end) as dir,
    sum(case when medium='Referral' then sessions end) as ref
FROM datatwo
GROUP BY date