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我不确定以下查询有什么问题。

对于提供names的大小/长度更大的数组，查询似乎运行得很慢（可能呈指数级缓慢，不确定）：

以下是 的列mytable：

name, timestamp, diff, diff2, ratio, minus_one

minus_onecolumn 只是一个辅助列，-1对于每个插入的行，它的值总是 。

有人可以帮助优化查询吗？或者你认为这很好吗？也许应该优化我的代码的其他部分以更快地运行它？任何建议都非常感谢。

询问：

SELECT 
    COUNT(diff) AS count, 
    IFNULL(AVG(diff), 0) AS avg, 
    IFNULL(MAX(diff), 0) AS max, 
    IFNULL(MIN(diff), 0) AS min 
FROM 
    mytable 
WHERE 
    name IN :names 
    AND timestamp >= :start 
    AND timestamp <= :end 
    AND ratio <> -1 
    AND (minus_one = :ratioStart OR ratio >= :ratioStart) 
    AND (minus_one = :ratioEnd OR ratio <= :ratioEnd) 
    AND (minus_one = :diffStart OR diff >= :diffStart)
    AND (minus_one = :diffEnd OR diff <= :diffEnd) 
    AND (minus_one = :diffStart2 OR diff2 >= :diffStart2) 
    AND (minus_one = :diffEnd2 OR diff2 <= :diffEnd2) 
GROUP BY 
    name 
ORDER BY 
    count DESC
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1 回答 1

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那是因为 where 子句需要更多时间来查询。您可以通过执行以下操作之一来改进查询：

  1. 使用多列索引：

    CREATE INDEX index_name ON table(col1, col2);

  2. 使用sqflite插件

于 2021-11-21T07:33:03.413 回答