Shulou(Shulou.com)06/01 Report--

(1) before optimization

The following SQL increases the salary of all pre-entry employees from 1985-05-21 to about 20.70s.

From the execution plan, we can see that the table salaries is fully indexed, with about 260W rows scanned.

Mysql > update salaries set salary=salary+500 where emp_no in (select emp_no from employees where hire_date desc update salaries set salary=salary+500 where emp_no in (select emp_no from employees where hire_date update salaries s join (select distinct e.emp_no from employees e where e.hire_date set. Salaryship) 500 potential query OK, 151583 rows affected (7.26 sec) Rows matched: 151583 Changed: 151583 Warnings: 0mysql > desc update salaries s join (select distinct e.emp_no from employees e where e.hire_date set s.salary=salary+500 +- +-+ | id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra | + -- + | 1 | PRIMARY | | NULL | ALL | NULL | 99827 | 100.00 | NULL | | 1 | UPDATE | s | | NULL | ref | PRIMARY | Emp_no | PRIMARY | 4 | e.emp_no | 10 | 100.00 | NULL | 2 | DERIVED | e | NULL | ALL | PRIMARY | NULL | 299512 | 33.33 | Using where | +-+ -+-+ 3 rows in set 1 warning (0.00 sec)

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