MySQL基础：数据库对象查看工具mysqlshow
mysql自带一个数据库查看工具，使用起来非常方便，本文对mysqlshow常见的使用方式进行介绍。
常见场景
mysql中的某一个schema，希望确认一下其中的数据库表的行数
很有可能你使用给一个简单的shell就完成了这个功能，你的脚本可能是这样写的（使用容器方式启动的mysql）
[root@host131 ~]# cat get_db_cnt.sh
#!/bin/sh
CONTAINER_NAME=mysql_mysql_1
DB_NAME=mysql
DB_USER=root
DB_PSWD=liumiaocn
execute_cmd(){
cmd="$*"
docker exec ${CONTAINER_NAME} mysql -u${DB_USER} -p${DB_PSWD} -e "use ${DB_NAME}; ${cmd};" 2>/dev/null
}
count_table(){
table="$1"
cnt=`docker exec ${CONTAINER_NAME} mysql -u${DB_USER} -p${DB_PSWD} -e "use ${DB_NAME}; select count(*) from ${table}" 2>/dev/null`
echo $cnt |awk '{print $2}'
}
ALL_TABLES=`execute_cmd "show tables" |grep -v "Tables_in_${DB_NAME}"`
for table in ${ALL_TABLES}
do
echo -n "$table "
count_table ${table}
done
[root@host131 ~]#
而执行则会得到这样的结果
[root@host131 ~]# sh get_db_cnt.sh
columns_priv 0
db 2
engine_cost 2
event 0
func 0
general_log 0
gtid_executed 0
help_category 40
help_keyword 681
help_relation 1339
help_topic 637
innodb_index_stats 1736
innodb_table_stats 289
ndb_binlog_index 0
plugin 0
proc 48
procs_priv 0
proxies_priv 1
server_cost 6
servers 0
slave_master_info 0
slave_relay_log_info 0
slave_worker_info 0
slow_log 0
tables_priv 1
time_zone 1811
time_zone_leap_second 0
time_zone_name 1811
time_zone_transition 121792
time_zone_transition_type 8771
user 2
[root@host131 ~]#
而如果你使用mysqlshow，则可以更简单地得到这样的结果
# mysqlshow -uroot -pliumiaocn mysql --count
mysqlshow: [Warning] Using a password on the command line interface can be insecure.
Database: mysql
+---------------------------+----------+------------+
| Tables | Columns | Total Rows |
+---------------------------+----------+------------+
| columns_priv | 7 | 0 |
| db | 22 | 2 |
| engine_cost | 6 | 2 |
| event | 22 | 0 |
| func | 4 | 0 |
| general_log | 6 | 0 |
| gtid_executed | 3 | 0 |
| help_category | 4 | 40 |
| help_keyword | 2 | 681 |
| help_relation | 2 | 1339 |
| help_topic | 6 | 637 |
| innodb_index_stats | 8 | 1736 |
| innodb_table_stats | 6 | 289 |
| ndb_binlog_index | 12 | 0 |
| plugin | 2 | 0 |
| proc | 20 | 48 |
| procs_priv | 8 | 0 |
| proxies_priv | 7 | 1 |
| server_cost | 4 | 6 |
| servers | 9 | 0 |
| slave_master_info | 25 | 0 |
| slave_relay_log_info | 9 | 0 |
| slave_worker_info | 13 | 0 |
| slow_log | 12 | 0 |
| tables_priv | 8 | 1 |
| time_zone | 2 | 1811 |
| time_zone_leap_second | 2 | 0 |
| time_zone_name | 2 | 1811 |
| time_zone_transition | 3 | 121792 |
| time_zone_transition_type | 5 | 8771 |
| user | 45 | 2 |
+---------------------------+----------+------------+
31 rows in set.
#
在一刹那，我们知道自己重复制造了一个既不好看也不是很好用的轮子。接下来我们来看一下这个已经有了的轮子常见的功能。
列出mysql中数据库信息
# mysqlshow -uroot -pliumiaocn
mysqlshow: [Warning] Using a password on the command line interface can be insecure.
+--------------------+
| Databases |
+--------------------+
| information_schema |
| devops |
| mysql |
| performance_schema |
| redmine |
| sonarqube |
| sys |
+--------------------+
#
查询包含的表的信息
类似与show tables，可以查询指定库包含那些表的信息
# mysqlshow -uroot -pliumiaocn mysql
mysqlshow: [Warning] Using a password on the command line interface can be insecure.
Database: mysql
+---------------------------+
| Tables |
+---------------------------+
| columns_priv |
| db |
| engine_cost |
| event |
| func |
| general_log |
| gtid_executed |
| help_category |
| help_keyword |
| help_relation |
| help_topic |
| innodb_index_stats |
| innodb_table_stats |
| ndb_binlog_index |
| plugin |
| proc |
| procs_priv |
| proxies_priv |
| server_cost |
| servers |
| slave_master_info |
| slave_relay_log_info |
| slave_worker_info |
| slow_log |
| tables_priv |
| time_zone |
| time_zone_leap_second |
| time_zone_name |
| time_zone_transition |
| time_zone_transition_type |
| user |
+---------------------------+
#
查询表中某一列的详细信息
# mysqlshow -uroot -pliumiaocn mysql user Host
mysqlshow: [Warning] Using a password on the command line interface can be insecure.
Database: mysql Table: user Wildcard: Host
+-------+----------+-----------+------+-----+---------+-------+---------------------------------+---------+
| Field | Type | Collation | Null | Key | Default | Extra | Privileges | Comment |
+-------+----------+-----------+------+-----+---------+-------+---------------------------------+---------+
| Host | char(60) | utf8_bin | NO | PRI | | | select,insert,update,references | |
+-------+----------+-----------+------+-----+---------+-------+---------------------------------+---------+
#
显示数据库的统计信息
前面我们使用mysqlshow -uroot -pliumiaocn mysql --count命令统计了mysql的内置mysql数据库的统计信息，如果不指定数据库，则是统计所有库的整体信息，具体执行示例如下所示：
# mysqlshow -uroot -pliumiaocn --count
mysqlshow: [Warning] Using a password on the command line interface can be insecure.
+--------------------+--------+--------------+
| Databases | Tables | Total Rows |
+--------------------+--------+--------------+
| information_schema | 61 | 23880 |
| devops | 140 | 874 |
| mysql | 31 | 138969 |
| performance_schema | 87 | 43576 |
| redmine | 55 | 274 |
| sonarqube | 45 | 4813 |
| sys | 101 | 10144 |
+--------------------+--------+--------------+
7 rows in set.
#
- 显示到表级别的统计信息
# mysqlshow -uroot -pliumiaocn mysql user --count
mysqlshow: [Warning] Using a password on the command line interface can be insecure.
Database: mysql Table: user Rows: 2
+------------------------+-----------------------------------+-----------------+------+-----+-----------------------+-------+---------------------------------+---------+
| Field | Type | Collation | Null | Key | Default | Extra | Privileges | Comment |
+------------------------+-----------------------------------+-----------------+------+-----+-----------------------+-------+---------------------------------+---------+
| Host | char(60) | utf8_bin | NO | PRI | | | select,insert,update,references | |
| User | char(32) | utf8_bin | NO | PRI | | | select,insert,update,references |
...省略
| account_locked | enum('N','Y') | utf8_general_ci | NO | | N | | select,insert,update,references | |
+------------------------+-----------------------------------+-----------------+------+-----+-----------------------+-------+---------------------------------+---------+
#
显示索引相关信息：-k
使用-k选项可以确认索引相关信息，以下为显示user表的索引信息的示例：
# mysqlshow -uroot -pliumiaocn mysql user -k
mysqlshow: [Warning] Using a password on the command line interface can be insecure.
Database: mysql Table: user
+------------------------+-----------------------------------+-----------------+------+-----+-----------------------+-------+---------------------------------+---------+
| Field | Type | Collation | Null | Key | Default | Extra | Privileges | Comment |
+------------------------+-----------------------------------+-----------------+------+-----+-----------------------+-------+---------------------------------+---------+
| Host | char(60) | utf8_bin | NO | PRI | | | select,insert,update,references | |
| User | char(32) | utf8_bin | NO | PRI | | | select,insert,update,references | |
| Select_priv | enum('N','Y') | utf8_general_ci | NO | | N | | select,insert,update,references | |
| Insert_priv | enum('N','Y') | utf8_general_ci | NO | | N | | select,insert,update,references | |
| Update_priv | enum('N','Y') | utf8_general_ci | NO | | N | | select,insert,update,references | |
| Delete_priv | enum('N','Y') | utf8_general_ci
...省略
| password_lifetime | smallint(5) unsigned | | YES | | | | select,insert,update,references | |
| account_locked | enum('N','Y') | utf8_general_ci | NO | | N | | select,insert,update,references | |
+------------------------+-----------------------------------+-----------------+------+-----+-----------------------+-------+---------------------------------+---------+
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| user | 0 | PRIMARY | 1 | Host | A | | | | | BTREE | | |
| user | 0 | PRIMARY | 2 | User | A | 2 | | | | BTREE | | |
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
#
可以看出Host和User两个字段是BTREE类型的索引(因为是主键的原因)。
显示表的状态信息：-i
使用-i选项可以确认表的状态信息，可以指定到库，也可以指定到表。指定到库用于显示所有表的信息，以下指定到表作为显示例子：
# mysqlshow -uroot -pliumiaocn mysql user -i
mysqlshow: [Warning] Using a password on the command line interface can be insecure.
Database: mysql Wildcard: user
+------+--------+---------+------------+------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+---------------------+------------+-----------+----------+----------------+-----------------------------+
| Name | Engine | Version | Row_format | Rows | Avg_row_length | Data_length | Max_data_length | Index_length | Data_free | Auto_increment | Create_time | Update_time | Check_time | Collation | Checksum | Create_options | Comment |
+------+--------+---------+------------+------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+---------------------+------------+-----------+----------+----------------+-----------------------------+
| user | MyISAM | 10 | Dynamic | 2 | 120 | 240 | 281474976710655 | 4096 | 0 | | 2018-10-28 20:58:59 | 2019-03-11 14:22:54 | | utf8_bin | | | Users and global privileges |
+------+--------+---------+------------+------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+---------------------+------------+-----------+----------+----------------+-----------------------------+
#