Show databases;
Show tables from db_name;
Show columns from table_name from db_name;
Show index from talbe_name [from db_name];
Show status;
Show variables;
Show [full] processlist;
Show table status [from db_name];
Show grants for user;
In addition to status, processlist, and grants, other options can contain the like wild option, which can use the SQL '%' and '_' characters;
Show databases like '% T ';
All databases whose names end with the 'T' character will be listed
Of course, in these SQL statements, you can also use db_name.table_name to replace table_name from db_name for easier writing!
If a user does not have any permissions for a table, the table will notSHOW TABLES
Ormysqlshow db_name
Shown in the output
You may still remember describe table_name, which achieves the same effect as show columns from db_name.table_name.
You can use mysqlshow -- status to get the same effect on show status.
Column |
Description |
Name |
Table Name |
Type |
Table type (ISAM, MyISAM, or HEAP) |
Row_format |
Row Storage Format (fixed, dynamic, or compressed) |
Rows |
Number of rows |
Avg_row_length |
Average line length |
Data_length |
Data File Length |
Max_data_length |
Maximum data file length |
Index_length |
Index file length |
Data_free |
Allocated but not used bytes |
Auto_increment |
Next autoincrement (automatically add 1) Value |
Create_time |
Table Creation Time |
Update_time |
Last Update Time of the data file |
Check_time |
Last time a check was run on the table |
Create_options |
AndCREATE TABLE Additional options used together |
Comment |
Note used when creating a table (or why MySQL cannot access some table information ). |
SHOW FIELDS
YesSHOW COLUMNS
A synonym,SHOW KEYS
YesSHOW INDEX
A synonym. You can also usemysqlshow db_name tbl_name
Ormysqlshow -k db_name tbl_name
Lists the columns or indexes of a table.
SHOW INDEX
Similar to ODBCSQLStatistics
The format of the call to return the index information. The following columns are returned:
Column |
Description |
Table |
Table Name |
Non_unique |
0. If the index cannot contain duplicates. |
Key_name |
Index name |
Seq_in_index |
The column sequence number in the index, starting from 1. |
Column_name |
Column name. |
Collation |
How columns are sorted in the index. InMySQL, Which can have a valueA (Ascending) orNULL (Not sorted ). |
Cardinality |
The number of unique values in the index. This can be done by runningisamchk -a Change. |
Sub_part |
If a column is partially indexed, the number of index characters is returned.NULL If the entire key is indexed. |
SHOW STATUS
Provide server status information (e.g.mysqladmin extended-status
). The output is similar to the following display, although the format and number can be a bit different:
+--------------------------+--------+
| Variable_name | Value |
+--------------------------+--------+
| Aborted_clients | 0 |
| Aborted_connects | 0 |
| Connections | 17 |
| Created_tmp_tables | 0 |
| Delayed_insert_threads | 0 |
| Delayed_writes | 0 |
| Delayed_errors | 0 |
| Flush_commands | 2 |
| Handler_delete | 2 |
| Handler_read_first | 0 |
| Handler_read_key | 1 |
| Handler_read_next | 0 |
| Handler_read_rnd | 35 |
| Handler_update | 0 |
| Handler_write | 2 |
| Key_blocks_used | 0 |
| Key_read_requests | 0 |
| Key_reads | 0 |
| Key_write_requests | 0 |
| Key_writes | 0 |
| Max_used_connections | 1 |
| Not_flushed_key_blocks | 0 |
| Not_flushed_delayed_rows | 0 |
| Open_tables | 1 |
| Open_files | 2 |
| Open_streams | 0 |
| Opened_tables | 11 |
| Questions | 14 |
| Slow_queries | 0 |
| Threads_connected | 1 |
| Threads_running | 1 |
| Uptime | 149111 |
+--------------------------+--------+
The state variables listed above have the following meanings:
Aborted_clients |
The number of dropped connections because the customer does not close the connection correctly. |
Aborted_connects |
The number of times the MySQL server has failed to be connected. |
Connections |
Number of attempts to connect to the MySQL server. |
Created_tmp_tables |
The number of implicit temporary tables that have been created when a statement is executed. |
Delayed_insert_threads |
The number of threads that are using the delayed insert processor. |
Delayed_writes |
UseINSERT DELAYED Number of lines written. |
Delayed_errors |
UseINSERT DELAYED Write errors (possibleDuplicate key value . |
Flush_commands |
RunFLUSH The number of times the command is executed. |
Handler_delete |
The number of times a row is deleted from a table. |
Handler_read_first |
The number of times the first row of the table is read. |
Handler_read_key |
The request number is based on the key-read row. |
Handler_read_next |
The number of times a single key-based row is read. |
Handler_read_rnd |
The number of times a request reads a row based on a fixed position. |
Handler_update |
The number of requests to update a row in the table. |
Handler_write |
The number of times a row is inserted into the table. |
Key_blocks_used |
The number of blocks used for keyword cache. |
Key_read_requests |
The number of times a key value is read from the cache. |
Key_reads |
The number of times a key value is physically read from a disk. |
Key_write_requests |
The number of times a keyword block is written to the cache. |
Key_writes |
The number of times a key-Value block is physically written to a disk. |
Max_used_connections |
The maximum number of connections used at the same time. |
Not_flushed_key_blocks |
The key block that has been changed in the key cache but has not been cleared to the disk. |
Not_flushed_delayed_rows |
InINSERT DELAY The number of rows waiting to be written in the queue. |
Open_tables |
The number of opened tables. |
Open_files |
The number of opened files. |
Open_streams |
Number of opened streams (mainly used for logging) |
Opened_tables |
The number of opened tables. |
Questions |
The number of queries sent to the server. |
Slow_queries |
Morelong_query_time Time query count. |
Threads_connected |
The number of currently opened connections. |
Threads_running |
Number of threads not sleeping. |
Uptime |
How many seconds does the server work. |
Notes:
- If
Opened_tables
Too big, so yourtable_cache
The variable may be too small.
- If
key_reads
Too big, so yourkey_cache
It may be too small. The cache hit rate can be used.key_reads
/key_read_requests
Computing.
- If
Handler_read_rnd
If it is too large, you may have a large number of queries that require MySQL to scan the entire table or that you have not correctly used the join key value ).
SHOW VARIABLES
Show someMySQLSystem variable value, you can also usemysqladmin variables
Command to obtain this information. If the default value is not suitable, you canmysqld
Use the command line option to set the majority of these variables at startup. The output is similar to the following display, although the format and number can be a bit different:
+ ------------------------ + -------------------------- +
| Variable_name | value |
+ ------------------------ + -------------------------- +
| Back_log | 5 |
| Connect_timeout | 5 |
| Basedir |/My/Monty/|
| Datadir |/My/Monty/data/|
| Delayed_insert_limit | 1, 100 |
| Delayed_insert_timeout | 300 |
| Delayed_queue_size | 1, 1000 |
| Join_buffer_size | 131072 |
| Flush_time | 0 |
| Interactive_timeout | 28800 |
| Key_buffer_size | 1048540 |
| Language |/my/monty/share/english/|
| Log | OFF |
| Log_update | OFF |
| Long_query_time | 10 |
| Low_priority_updates | OFF |
| Max_allowed_packet| 1048576 |
| Max_connections | 100 |
| Max_connect_errors | 10 |
| Max_delayed_threads | 20 |
| Max_heap_table_size | 16777216 |
| Max_join_size | 4294967295 |
| Max_sort_length | 1024 |
| Max_tmp_tables | 32 |
| Net_buffer_length | 16384 |
| Port | 1, 3306 |
| Protocol-version | 10 |
| Record_buffer | 131072 |
| Skip_locking | ON |
| Socket |/tmp/mysql. sock |
| Sort_buffer | 2097116 |
| Table_cache | 64 |
| Thread_stack | 131072 |
| Tmp_table_size | 1048576 |
| Tmpdir |/machine/tmp/|
| Version | 3.23.0-alpha-Debug |
| Wait_timeout | 28800 |
+ ------------------------ + -------------------------- +SHOW PROCESSLIST
Shows which thread is running. You can also usemysqladmin processlist
Command to obtain this information.
If you haveProcessPermission, you can see all the threads, otherwise, you can only see your own threads.
See 7.20 KILL
Syntax. If you do not useFULL
Then, each query is only displayed with the first 100 characters.
SHOW GRANTS FOR user
Lists authorization commands that must be repeatedly authorized to a user.
mysql> SHOW GRANTS FOR root@localhost;
+---------------------------------------------------------------------+
| Grants for root@localhost |
+---------------------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'root''localhost' WITH GRANT OPTION |
+---------------------------------------------------------------------+
Original article link: http://www.busfly.cn/csdn/post/MySQL-show-get-database-info.html