MySQL8 explain

explain

output

Table 8.1 EXPLAIN Output Columns

Column	JSON Name	Meaning
id	select_id	The SELECT identifier
select_type	None	The SELECT type
table	table_name	The table for the output row
partitions	partitions	The matching partitions
type	access_type	The join type
possible_keys	possible_keys	The possible indexes to choose
key	key	The index actually chosen
key_len	key_length	The length of the chosen key
ref	ref	The columns compared to the index
rows	rows	Estimate of rows to be examined
filtered	filtered	Percentage of rows filtered by table condition
Extra	None	Additional information

EXPLAIN FORMAT=TREE

显示查询计划和成本估算

explain  format=tree
SELECT *
FROM `order`
WHERE shop_id = xxx and (corp_id = xxx) 
ORDER BY create_time DESC
LIMIT 10
--- 输出
-> Limit: 10 row(s)  (cost=9379.88 rows=10)
    -> Index range scan on order using idx_shopid_corpid_createtime, with index condition: ((`order`.corp_id = xxx) and (`order`.shop_id = xxxx))  (cost=9379.88 rows=13070)

explain analyze

EXPLAIN ANALYZE 是一个用于查询的分析工具，向用户显示 MySQL 在查询上花费的时间以及原因。
它将产生查询计划，并对其进行检测和执行，同时计算行数并度量执行计划中不同点上花费的时间。执行完成后，EXPLAIN ANALYZE 将输出计划和度量结果，而不是查询结果。

reference

• mysql doc
• 知乎:mysql explain analyze
• tool,tableconvert: csv to markdown