Mysql quick statement for adding millions of records

When using the Insert Select statement to Insert a record, you must follow the following principles.
When selecting data using the Select statement, you cannot Select rows from the table to which the data is inserted.
The number of fields in the inserted table must be the same as the number of fields returned by the Select statement.
The field data type after the inserted table must be the same as that returned by the Select statement or can be automatically converted.
 Copy codeThe Code is as follows:
Insert into ler_items (classid, title, address, zipcode)
SELECT classid, title, address, zipcode
FROM ler_items

Using the preceding SQL statement, you can add millions of records to the ler_items table in a short period of time, which is helpful for database testing.