MySQL returns an entry and exit data ID when inserting data

INSERT into User_info (name,gender,height,age) VALUES (' sa ', ' female ', ' 120 ', ' 12 '); SELECT @ @IDENTITY

@ @identity is a system-defined global variable that represents the last time the value of the self-increment column for inserting data into a table with the identity attribute (that is, the self-increment column). General system-defined global variables start with @@ 开头
User-defined variables begin with @. For example, there is a table A, its self-increment column is an ID, when inserting a row of data into a table, if the value of the self-increment after inserting data automatically increases to 101, then the value obtained by the SELECT @ @identity is 101.
The @ @identity is used only if the connection is not closed when the SELECT @ @identity is executed after the insert operation, otherwise the resulting value will be null------Baidu

MySQL returns an entry and exit data ID when inserting data