Whether the SQL is indexed

Use Explain Command to view the execution plan of the statement
example ：Explain select * from table
Excepting select, Others like insert,update and delete Can be used explain View execution plan
A general description ：
id: Select the identifier
select_type: Represents the type of query .
table: Output result set table
partitions: Matching partition
type: Indicates the connection type of the table ：ALL、index、range、 ref、eq_ref、const、system、NULL（ From left to right , Performance from poor to good ）
possible_keys: Possible indexes
key: Actual index used
key_len: Length of index field
ref: Comparison of columns and indexes
rows: Number of lines scanned ( The estimated number of lines )
filtered: Percentage of rows filtered by table criteria
Extra: Description and description of implementation
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Link to the original text ：https://blog.csdn.net/yao583224426/article/details/121691683
author ： I love spicy

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