MySQL 45 lecture learning notes (XIII) delete half of the table data, and the table file size remains the same

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• One InnoDB The table consists of two parts , That is, table structure definition and data
• stay MySQl8.0 Table structure exists .frm In the file for suffix .
• MySQL8.0 edition , It is allowed to put the table structure definition in the system data table
• Because the table structure definition takes up very little space

Parameters innodb_file_per_table

        The number of tables can be stored in the shared table space , It can also be a separate file , This behavior is a parameter innodb_file_per_table The control of the ;

• This parameter is set to OFF Express ： The data of the table is placed in the shared table space of the system , That is, data dictionary
• This parameter ON Express ： Every InnoDB Table data is stored in one with .ibd In the file with suffix .

MySQL5.6.6 Version start , His The default value is ON

• It's easier to manage a table as a single file
• When you don't need this watch , adopt drop table command , The system will delete this file directly
• If you put it on a shared table space , Even if the table is deleted , Space will not be recycled