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优化查询时需要帮助

performance phpmyadmin join mysql php

Simon · 技术社区 · 15 年前

incoming tours(id,name) 和 incoming_tours_cities(id_parrent, id_city)

id 在第一个表中是唯一的,对于第一个表中的每一个唯一行,都有 id_city -在第二个表中(即。 id_parrent 身份证件 从第一张桌子)

incoming_tours

|--id--|------name-----|
|---1--|---first_tour--|
|---2--|--second_tour--|
|---3--|--thirth_tour--|
|---4--|--hourth_tour--|

incoming_tours_cities

|-id_parrent-|-id_city-|
|------1-----|---4-----|
|------1-----|---5-----|
|------1-----|---27----|
|------1-----|---74----|
|------2-----|---1-----|
|------2-----|---5-----|
........................

也就是说 first_tour 有城市列表- ("4","5","27","74")

以及 second_tour 有城市列表- ("1","5")

4 和 74 :

现在,我需要从第一个表中获取所有行 二者都 值在城市列表中。i、它必须只返回 第一次参观 (因为有4个和74个在城市名单上)

所以,我写了下面的查询

SELECT t.name
FROM `incoming_tours` t
JOIN `incoming_tours_cities` tc0 ON tc0.id_parrent = t.id
AND tc0.id_city = '4'
JOIN `incoming_tours_cities` tc1 ON tc1.id_parrent = t.id
AND tc1.id_city = '74'

但我是动态生成查询的,当连接数很大(大约15个)时,查询速度会减慢。

i、当我试着跑的时候

SELECT t.name
FROM `incoming_tours` t
JOIN `incoming_tours_cities` tc0 ON tc0.id_parrent = t.id
AND tc0.id_city = '4'
JOIN `incoming_tours_cities` tc1 ON tc1.id_parrent = t.id
AND tc1.id_city = '74'
.........................................................
JOIN `incoming_tours_cities` tc15 ON tc15.id_parrent = t.id
AND tc15.id_city = 'some_value'

查询运行已进入 45s (尽管我在表中设置了索引)

多谢

6 回复 | 直到 15 年前

ksogor 15 年前

SELECT t.name
FROM incoming_tours t INNER JOIN 
  ( SELECT id_parrent
    FROM incoming_tours_cities
    WHERE id IN (4, 74)
    GROUP BY id_parrent
    HAVING count(id_city) = 2) resultset 
  ON resultset.id_parrent = t.id

但你需要改变城市总数。

Narf 15 年前

SELECT name
FROM (
      SELECT DISTINCT(incoming_tours.name) AS name,
             COUNT(incoming_tours_cities.id_city) AS c
      FROM incoming_tours
           JOIN incoming_tours_cities
                ON incoming_tours.id=incoming_tours_cities.id_parrent
      WHERE incoming_tours_cities.id_city IN(4,74)
            HAVING c=2
      ) t1;

你得换衣服 c=2 id_city 您正在搜索,但是由于您动态生成查询,所以这不应该是问题。

Aether 15 年前

SELECT * FROM incoming_tours 
WHERE 
id IN (SELECT id_parrent FROM incoming_tours_cities WHERE id_city=4)
AND id IN (SELECT id_parrent FROM incoming_tours_cities WHERE id_city=74)
...
AND id IN (SELECT id_parrent FROM incoming_tours_cities WHERE id_city=some_value)

Luca Martini 15 年前

只是个提示。 IN a中的运算符 WHERE 条款,你可以希望操作员的短路 AND 可能会消除不必要的 JOIN 在执行不遵守约束的巡更期间。

pharalia 15 年前

这是个奇怪的查询方式

SELECT t.name FROM `incoming_tours` as t WHERE t.id IN (SELECT id_parrent FROM `incoming_tours_cities` as tc WHERE tc.id_city IN ('4','74'));

我认为

编辑:向子查询添加表别名

Catch22 15 年前

我使用CTE编写了这个查询,它在查询中包含测试数据。您需要修改它,以便它查询实际的表。不确定它如何在大型数据集上执行。。。

Declare @numCities int = 2

;with incoming_tours(id, name) AS
(
    select 1, 'first_tour' union all
    select 2, 'second_tour' union all
    select 3, 'third_tour' union all
    select 4, 'fourth_tour' 
)
, incoming_tours_cities(id_parent, id_city) AS
(
    select 1, 4 union all 
    select 1, 5 union all 
    select 1, 27 union all 
    select 1, 74 union all 
    select 2, 1 union all 
    select 2, 5
)
, cityIds(id_city) AS
( 
    select 4
    union all select 5
    /* Add all city ids you need to check in this table */
)
, common_cities(id_city, tour_id, tour_name) AS
(
    select c.id_city,  it.id, it.name
    from cityIds C, Incoming_tours_cities tc, incoming_tours it
    where C.id_city = tc.id_city
    and tc.id_parent = it.id
)
, tours_with_all_cities(id_city) As
(
    select tour_id from common_cities 
    group by tour_id 
    having COUNT(id_city) = @numCities
)
select it.name from incoming_tours it, tours_with_all_cities tic
where it.id = tic.id_city