Shulou(Shulou.com)05/31 Report--

In this issue, the editor will bring you about the connection mode of the implementation plan in Mysql SQL optimization. The article is rich in content and analyzes and describes for you from a professional point of view. I hope you can get something after reading this article.

Although the idea of SQL tuning of relational database is the same, and the specific methods and steps are more or less the same, the details can not be ignored, especially in the interpretation of the specific details of the implementation plan, each relational database is indeed different, especially the mysql database, which is more different from other relational databases. Below, we only briefly introduce and explain the most common connection methods in the SQL implementation plan.

System: a system table which is a constant table (access to a constant system table)

Const: a constant table (access to a constant scale)

Eq_ref: a unique or primary index with an equality relation (access to a unique or primary key index through an equivalent operation)

Ref: an index with an equality relation, where the index value cannot be NULL (access an index that does not contain a null value through an equivalent operation)

Ref_or_null: an index with an equality relation, where it is possible for the index value to be NULL (access to a null that may be worth indexing through an equivalent operation)

Range: an index with a relation such as BETWEEN, IN, > =, LIKE, and so on (access an index through operations such as between,in, > =, like, etc.)

Using_index:a covering index is used (access an index by overriding an index)

Index: a sequential scan on an index (accessing an index through sequential scanning)

ALL: a sequential scan of the entire table (access the entire table through sequential scans).

In addition, in mysql, no matter the access operation to the table or index or the join operation between multiple tables, it is generally referred to as join. Here, we should pay attention to it.

The above is the connection mode of the execution plan in the Mysql SQL optimization shared by the editor. If you happen to have similar doubts, you might as well refer to the above analysis to understand. If you want to know more about it, you are welcome to follow the industry information channel.

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