Question

我对子查询和自连接有以下查询：

SELECT bucket.patient_sid AS sid
FROM 
(SELECT clinical_data.patient_sid, 
        clinical_data.lft, 
        clinical_data.rgt
FROM clinical_data INNER JOIN 
(SELECT clinical_data.patient_sid, 
        clinical_data.lft, 
        clinical_data.rgt, 
        clinical_data.attribute_id 
FROM clinical_data 
WHERE clinical_data.attribute_id = '33' AND clinical_data.string_value = '2160-0') AS attribute 
ON clinical_data.patient_sid = attribute.patient_sid 
    AND clinical_data.lft >= attribute.lft 
    AND clinical_data.rgt <= attribute.rgt 
WHERE clinical_data.attribute_id = '36') AS bucket;

我在此定义了以下索引：

KEY `idx_bucket` (`attribute_id`,`string_value`)
KEY `idx_self_join` (`patient_sid`,`attribute_id`,`lft`,`rgt`)

当我使用EXPLAIN查看查询时，使用覆盖索引idx_bucket的子查询肯定是优化的，但是self join和where子句不是。此外，为什么在patient_sid，attribute_id显示used_key_parts时，报告attachment_condition仅使用lft和rgt这是否意味着？）。 lft和'rgt`都只是定义为没有特殊属性的整数，为什么它们不在我的覆盖索引中使用？

当我定义

时更奇怪

KEY `idx_self_join` (`patient_sid`,`lft`,`rgt`,`attribute_id`)

仅在patient_sid中注册了used_key_parts. filtered 1.60%从11.00%下降到{ "query_block": { "select_id": 1, "cost_info": { "query_cost": "645186.71" }, "nested_loop": [ { "table": { "table_name": "clinical_data", "access_type": "ref", "possible_keys": [ "fk_attribute_idx", "idx_value_string", "idx_value_double", "idx_bucket", "idx_self_join_idx" ], "key": "idx_bucket", "used_key_parts": [ "attribute_id", "string_value" ], "key_length": "308", "ref": [ "const", "const" ], "rows_examined_per_scan": 126402, "rows_produced_per_join": 126402, "filtered": "100.00", "cost_info": { "read_cost": "126402.00", "eval_cost": "25280.40", "prefix_cost": "151682.40", "data_read_per_join": "46M" }, "used_columns": [ "patient_sid", "string_value", "attribute_id", "lft", "rgt" ], "attached_condition": "(`ns_large2`.`clinical_data`.`patient_sid` is not null)" } }, { "table": { "table_name": "clinical_data", "access_type": "ref", "possible_keys": [ "fk_attribute_idx", "idx_value_string", "idx_value_double", "idx_bucket", "idx_self_join_idx" ], "key": "idx_self_join_idx", "used_key_parts": [ "attribute_id", "patient_sid" ], "key_length": "10", "ref": [ "const", "ns_large2.clinical_data.patient_sid" ], "rows_examined_per_scan": 14, "rows_produced_per_join": 201169, "filtered": "11.11", "using_index": true, "cost_info": { "read_cost": "131327.39", "eval_cost": "40233.83", "prefix_cost": "645186.71", "data_read_per_join": "73M" }, "used_columns": [ "patient_sid", "attribute_id", "lft", "rgt" ], "attached_condition": "((`ns_large2`.`clinical_data`.`lft` >= `ns_large2`.`clinical_data`.`lft`) and (`ns_large2`.`clinical_data`.`rgt` <= `ns_large2`.`clinical_data`.`rgt`))" } } ] } }！

Xrm.Utility.openEntityForm()

Answer 1

这是您的基本加入：

SELECT

FROM clinical_data cd1

JOIN clinical_data cd2
    ON cd1.patient_sid = cd2.patient_sid
    AND cd2.attribute_id = '33'

WHERE cd1.attribute_id = '36'

Answer 2

这是我最终想出的：

SELECT
    cd1.patient_sid as sid

FROM clinical_data cd1

JOIN clinical_data cd2
    ON cd1.patient_sid = cd2.patient_sid
    AND cd1.lft >= cd2.lft 
    AND cd1.rgt <= cd2.rgt 

WHERE cd1.attribute_id = '36'
    AND cd2.attribute_id = '33'
    AND cd2.string_value = '2160-0'

Answer 3

＆＃34; Used_columns＆＃34;说＆＃39;覆盖＆＃39;。最后的＆＃34;使用过的关键部分＆＃34;不是全部用作＆＃34;键＆＃34;因为他们需要在＆＃34;范围内＆＃34;而不是＆＃39; =＆＃39;。

摆脱外部查询：

<!DOCTYPE html>
<html lang="pt-PT">

<head>
  <meta charset="UTF-8">
  <title>High School</title>
</head>

<body>
  <div id="school"></div>
</body>

</html>

很抱歉，但是lft-rgt架构效率不高。

使用覆盖索引优化查询

3 个答案: