SQL_BIG_SELECTS 错误

Posted 2023-02-24

【中文标题】SQL_BIG_SELECTS 错误

【英文标题】：SQL_BIG_SELECTS error

【发布时间】：2017-08-22 11:07:20

【问题描述】：

更新

现在我可以通过删除 ORDER BY... 来使其工作...不确定这是正确的做法，但必须这样做。

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首先，这是我要加入数据库的所有表中的所有字段（列）

突出显示的字段是我要选择的字段。

所以，我写了 sql 语法来像这样连接所有表

SELECT country_policies.policyname,
       country_policies.countryname,
       section_data_structure.data_name,
       section_data_content_p.dropname,
       section_data_content_p.comment,
       date_format(section_data_content_p.start_date,'%Y-%m-%d') as start_date,
       date_format(section_data_content_p.end_date,'%Y-%m-%d') as end_date,
       section_data_content_p.policy_id,
       section_data_content_p.country_id,
       sections_content.section_id,
       sections_content.statecode
FROM
(
    (country_policies
     INNER JOIN section_data_content_p
         ON country_policies.policyid = section_data_content_p.policy_id AND
            country_policies.countryid = section_data_content_p.country_id
    )
    INNER JOIN section_data_structure
        ON section_data_content_p.data_structure_id = section_data_structure.id
    INNER JOIN sections_content
        ON section_data_content_p.state_id = sections_content.statecode
)
order by section_data_content_p.dropname;

然后我得到了这个错误

ER_TOO_BIG_SELECT：SELECT 将检查超过 MAX_JOIN_SIZE 行；检查您的 WHERE 并使用 SET SQL_BIG_SELECTS=1 或 SET MAX_JOIN_SIZE=# 如果 SELECT 没问题

所以我尝试添加 SET SQL_BIG_SELECTS= 1 ;像这样爬到顶端

SET SQL_BIG_SELECTS= 1 ;
SELECT country_policies.policyname, country_policies.countryname, section_data_structure.data_name, section_data_content_p.dropname, section_data_content_p.comment, date_format(section_data_content_p.start_date,'%Y-%m-%d') as start_date, date_format(section_data_content_p.end_date,'%Y-%m-%d') as end_date,section_data_content_p.policy_id,section_data_content_p.country_id,sections_content.section_id,sections_content.statecode
FROM  ((country_policies
INNER JOIN section_data_content_p ON country_policies.policyid = section_data_content_p.policy_id AND country_policies.countryid = section_data_content_p.country_id)
INNER JOIN section_data_structure ON section_data_content_p.data_structure_id = section_data_structure.id
INNER JOIN sections_content ON section_data_content_p.state_id = sections_content.statecode) order by section_data_content_p.dropname;

然后又报错了

ER_PARSE_ERROR：您的 SQL 语法有错误；检查与您的 mysql 服务器版本相对应的手册，以获取在 'SET SQL_BIG_SELECTS= 1 附近使用的正确语法 SELECT country_policies.policyname, country_policies.co' 在第 1 行

也尝试过 SET SESSION/SET OPTION 但都不起作用 我仍然无法解决这个问题。 mysql版本是5.6.32

有人可以帮忙吗？谢谢

【问题讨论】：

***.com/questions/950465/mysql-sql-big-selects

这些表有多大？我从来没有遇到过too-large-for-select 错误，但我可以建议您尝试改写您的查询以避免有这么多的中间行。您打算返回多少行？如果远小于阈值，那么也许您可以重写您的查询。

@TimBiegeleisen 我认为会超过 10,000 行

【参考方案1】：

我已经整理了您的两个代码示例中的一些括号用法。第一个是现在...

SELECT country_policies.policyname,
       country_policies.countryname,
       section_data_structure.data_name,
       section_data_content_p.dropname,
       section_data_content_p.comment,
       DATE_FORMAT( section_data_content_p.start_date,
                    '%Y-%m-%d' ) AS start_date,
       DATE_FORMAT( section_data_content_p.end_date,
                    '%Y-%m-%d' ) AS end_date,
       section_data_content_p.policy_id,
       section_data_content_p.country_id,
       sections_content.section_id,
       sections_content.statecode
FROM country_policies
     INNER JOIN section_data_content_p ON ( country_policies.policyid = section_data_content_p.policy_id AND country_policies.countryid = section_data_content_p.country_id )
     INNER JOIN section_data_structure ON section_data_content_p.data_structure_id = section_data_structure.id
     INNER JOIN sections_content ON section_data_content_p.state_id = sections_content.statecode
ORDER BY section_data_content_p.dropname;

我也将 SQL_BIG_SELECT 设置为会话变量，按照修改后的第二段代码中的MySQL - SQL_BIG_SELECTS，如下...

SET SESSION SQL_BIG_SELECTS = 1;
SELECT country_policies.policyname,
       country_policies.countryname,
       section_data_structure.data_name,
       section_data_content_p.dropname,
       section_data_content_p.comment,
       DATE_FORMAT( section_data_content_p.start_date,
                    '%Y-%m-%d' ) AS start_date,
       DATE_FORMAT( section_data_content_p.end_date,
                    '%Y-%m-%d' ) AS end_date,
       section_data_content_p.policy_id,
       section_data_content_p.country_id,
       sections_content.section_id,
       sections_content.statecode
FROM country_policies
     INNER JOIN section_data_content_p ON ( country_policies.policyid = section_data_content_p.policy_id AND country_policies.countryid = section_data_content_p.country_id )
     INNER JOIN section_data_structure ON section_data_content_p.data_structure_id = section_data_structure.id
     INNER JOIN sections_content ON section_data_content_p.state_id = sections_content.statecode
ORDER BY section_data_content_p.dropname;

注意：我还将布局更改为我觉得更容易调试的样式。

如果您有任何问题或cmets，请随时发表相应的评论。

【参考方案2】：

SET max_join_size=18446744073709551615 那么你可能会输掉大选择。

【讨论】：

对 ON 子句中使用的列进行索引更合乎逻辑，因为我很确定那些没有被索引..