SQL NOT IN子查询导致性能下降的问题

Question

我想使用表格来检查街道。

1. 查询不是最优的
2. 查询时间太长

有人可以帮助我吗

SELECT id, strasse, plz
FROM `adress`
WHERE strasse NOT IN (
    SELECT street
    FROM post_plz
    WHERE `street` like adress.strasse AND plz like adress.plz
)
LIMIT 5;

Answer 1

SELECT id, strasse, plz
FROM adress
WHERE NOT EXISTS ( SELECT NULL
                   FROM post_plz
                   WHERE post_plz.street = adress.strasse 
                     AND post_plz.plz = adress.plz )
-- ORDER BY {expression}  
LIMIT 5

没有使用ORDER BY时，查询结果是非确定性的（两次查询可能产生不同的结果）。因此强烈建议添加一些行排序。

索引post_plz (adress, plz)和adress (strasse, plz, id)必须进行优化。

Answer 2

You could try using aleft join between the table and check for not mactching values

SELECT id, strasse, plz 

from `adress` 
left join  post_plz on strasse = street
  AND `street` like adress.strasse 
    AND plz like adress.plz
WHERE street is null
 LIMIT 5;

你可以尝试在表之间使用左连接，并检查不匹配的值

SELECT id, strasse, plz 

from `adress` 
left join  post_plz on strasse = street
  AND `street` like adress.strasse 
    AND plz like adress.plz
WHERE street is null
 LIMIT 5;