mysql> select sn,id,info from s100 group by id;

+-----+------+------+

| sn  | id   | info |

+-----+------+------+

| 227 |    1 | aa   |

| 228 |    2 | bb   |

+-----+------+------+

2 rows in set (0.02 sec)

mysql> select sn,count(id),info from s100 group by id;

+-----+-----------+------+

| sn  | count(id) | info |

+-----+-----------+------+

| 227 |     32768 | aa   |

| 228 |         1 | bb   |

+-----+-----------+------+

2 rows in set (0.02 sec)

mysql>

mysql>

mysql> show index from s100;

+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |

+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

| s100  |          0 | PRIMARY  |            1 | sn          | A         |       33366 |     NULL | NULL   |      | BTREE      |         |               |

+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

1 row in set (0.00 sec)

mysql>  show variables like '%tx_isolation%';

+---------------+----------------+

| Variable_name | Value          |

+---------------+----------------+

| tx_isolation  | READ-COMMITTED |

+---------------+----------------+

1 row in set (0.00 sec)

mysql> show variables like '%commit%';

+--------------------------------+-------+

| Variable_name                  | Value |

+--------------------------------+-------+

| autocommit                     | OFF   |

| binlog_order_commits           | ON    |

| innodb_api_bk_commit_interval  | 5     |

| innodb_commit_concurrency      | 0     |

| innodb_flush_log_at_trx_commit | 1     |

+--------------------------------+-------+

5 rows in set (0.00 sec)

Session 1:

mysql> select * from s100 where id=2 for update;

+-----+------+------+

| sn  | id   | info |

+-----+------+------+

| 228 |    2 | bb   |

+-----+------+------+

1 row in set (0.02 sec)

Session 2:

Database changed

mysql> insert into s100(id,info) values(9999,'fcadfad');

Query OK, 1 row affected (0.00 sec)

RC模式下,是行锁 不会上升到表级锁