[英]MySQL Issue: Inner Join with Subquery returning no results
我有一個數據庫,其中包含一組具有不同表單版本版本的表單。 下面的“有效”查詢按每個表單版本的批准使用日期成功選擇了最新的表單版本。
我想將此查詢“工作”查詢與另一個表“ forms_types”結合起來,該表返回“ form_type”列的全文描述。
我這樣做的嘗試不起作用-我也應該在查詢的“聯接”版本上獲得50個結果,但它不返回任何結果。
讓我的工作查詢正確加入,將不勝感激!
工作(50個結果,但沒有JOIN):
SELECT *
FROM forms AS t
WHERE california =
(
SELECT MAX(california)
FROM forms
WHERE `form_number` = t.`form_number`
AND trucking_coverage= 1
AND california IS NOT NULL
AND california <= '2014-01-29'
AND form_type <> 0
)
ORDER BY `t`.`form_type` ASC, `t`.`form_number` ASC
不起作用(無結果):
SELECT *
FROM forms AS t
INNER JOIN forms_types
ON 'forms.form_type' = 'forms_types.form_type'
WHERE california =
(
SELECT MAX(california)
FROM forms
WHERE `form_number` = t.`form_number`
AND trucking_coverage= 1
AND california IS NOT NULL
AND california <= '2014-01-29'
AND form_type <> 0
)
ORDER BY `t`.`form_type` ASC, `t`.`form_number` ASC
您是否正在尋找這樣的東西?
SELECT f.*, t.*
FROM
(
SELECT form_number, MAX(california) california
FROM forms
WHERE trucking_coverage = 1
AND california IS NOT NULL
AND california <= '2014-01-29'
AND form_type <> 0
GROUP BY form_number
) q JOIN forms f
ON q.form_number = f.form_number
AND q.california = f.california JOIN forms_types t
ON f.form_type = t.form_type
ORDER BY f.form_type, f.form_number
也可以用這種方式重寫(通過利用非標准的MySQL GROUP BY
擴展名)
SELECT *
FROM
(
SELECT *
FROM forms f JOIN forms_types t
ON f.form_type = t.form_type
WHERE f.trucking_coverage = 1
AND f.california IS NOT NULL
AND f.california <= '2014-01-29'
AND f.form_type <> 0
ORDER BY california DESC
) q
GROUP BY f.form_number
ORDER BY f.form_type, f.form_number
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