When MySQL inserts data, it removes duplicate data;

1. Use the insert ignore into statement to re-

Mysql> INSERTIGNORE intoperson_tbl (last_name, first_name) - VALUES('J','T'); Query OK,1Row affected (0.00sec) MySQL> INSERTIGNORE intoperson_tbl (last_name, first_name) - VALUES('J','T'); Query OK,0Rows Affected (0.00Sec

2. Query filtering Duplicate data

①. Using the MySQL keyword distinct to remove weight

MySQL>SELECTDISTINCT  last_name, first_name      from Person_tbl;

②. Using GROUP by to carry out the heavy

MySQL>SELECT  last_name, first_name    from  person_tbl      - GROUP  by (last_name, first_name);

3. Delete duplicate data from a table

Idea: first create a temporary table, the non-duplicated data in the temporary table, and then delete the original table, and then rename the temporary table into a formal table

MySQL>CREATETABLESELECT from person_tbl  GROUPby  (last_name, first_name, sex); MySQL>DROPTABLE  person_tbl; MySQL>ALTERTABLE to Person_tbl;

When MySQL inserts data, it removes duplicate data;