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MySQL - SHOW OPEN TABLES Statement
SHOW OPEN TABLES Statement
The CREATE TABLE statement is used to create tables in MYSQL database. Here, you need to specify the name of the table and, definition (name and datatype) of each column.
The SHOW OPEN TABLES statement displays the lists the non-TEMPORARY tables which are currently open in the table cache. In addition to names of the tables this statement also provides the name of the database the table is in and binary values (0 or 1) specifying whether the table is in use and if it is locked.
Syntax
Following is the syntax of the SHOW OPEN TABLES Statement −
SHOW OPEN TABLES [{FROM | IN} db_name] [LIKE 'pattern' | WHERE expr]
Example
Following statement displays the information about the tables that are currently open in the table cache −
SHOW OPEN TABLES\G;
Output
The above query produces the following output −
************* 1. row ************* Database: mysql Table: check_constraints In_use: 0 Name_locked: 0 ************* 2. row ************* Database: mysql Table: column_type_elements In_use: 0 Name_locked: 0 ************* 3. row ************* Database: mysql Table: slave_master_info In_use: 0 Name_locked: 0 ************* 4. row ************* Database: mysql Table: foreign_keys In_use: 0 Name_locked: 0 ************* 5. row ************* Database: mysql Table: columns In_use: 0 Name_locked: 0 ************* 6. row ************* Database: mysql Table: foreign_key_column_usage In_use: 0 Name_locked: 0 ************* 7. row ************* Database: mysql Table: server_cost In_use: 0 Name_locked: 0 ************* 8. row ************* Database: mysql Table: index_column_usage In_use: 0 Name_locked: 0 ************* 9. row ************* Database: mysql Table: view_table_usage In_use: 0 Name_locked: 0 ************* 10. row ************* Database: mysql Table: index_partitions In_use: 0 Name_locked: 0 ************* 11. row ************* Database: mysql Table: indexes In_use: 0 Name_locked: 0 ************* 12. row ************* Database: mysql Table: schemata In_use: 0 Name_locked: 0 ************* 13. row ************* Database: mysql Table: collations In_use: 0 Name_locked: 0 ************* 14. row ************* Database: mysql Table: table_partition_values In_use: 0 Name_locked: 0 ************* 15. row ************* Database: mysql Table: table_partitions In_use: 0 Name_locked: 0 ************* 16. row ************* Database: mysql Table: tables In_use: 0 Name_locked: 0 ************* 17. row ************* Database: mysql Table: role_edges In_use: 0 Name_locked: 0 ************* 18. row ************* Database: mysql Table: triggers In_use: 0 Name_locked: 0 ************* 19. row ************* Database: test Table: contact In_use: 0 Name_locked: 0 ************* 20. row ************* Database: mysql Table: column_statistics In_use: 0 Name_locked: 0 ........................ ........................ ........................
FROM or IN clause
You can retrieve information about the non-TEMPORARY tables that are currently open in the table cache from a specific database using the FROM clause.
SHOW OPEN TABLES FROM performance_schema;
Output
Following is the output of the above query −
Database | Table | In_use | Name_locked |
---|---|---|---|
performance_schema | events_waits_history_long | 0 | 0 |
performance_schema | session_status | 0 | 0 |
performance_schema | events_stages_history_long | 0 | 0 |
performance_schema | events_statements_current | 0 | 0 |
performance_schema | session_variables | 0 | 0 |
performance_schema | threads | 0 | 0 |
You can also use the IN clause instead of FROM as −
SHOW OPEN TABLES IN performance_schema;
Output
After executing the above query, it will produce the following output −
Database | Table | In_use | Name_locked |
---|---|---|---|
performance_schema | events_waits_history_long | 0 | 0 |
performance_schema | session_status | 0 | 0 |
performance_schema | events_stages_history_long | 0 | 0 |
performance_schema | events_statements_current | 0 | 0 |
performance_schema | session_variables | 0 | 0 |
performance_schema | threads | 0 | 0 |
The LIKE clause
Using the LIKE clause, you can specify a pattern to retrieve information about specific tables that are currently open in the table cache. Following query retrieves description about the tables with name starting with the word "information".
SHOW OPEN TABLES LIKE 'time%';
Output
Once the query is executed, it will produce the output shown below −
Database | Table | In_use | Name_locked |
---|---|---|---|
mysql | time_zone_transition | 0 | 0 |
mysql | time_zone_leap_second | 0 | 0 |
mysql | time_zone_name | 0 | 0 |
mysql | time_zone | 0 | 0 |
mysql | time_zone_transition_type | 0 | 0 |
The WHERE clause
You can use the WHERE clause of the SHOW OPEN TABLES statements to retrieve description of the variables which match the specified condition.
Example
Assume we have created a table that contains the sales details as shown below −
CREATE TABLE SalesDetails ( ID INT, ProductName VARCHAR(255), CustomerName VARCHAR(255), DispatchDate date, DeliveryTime time, Price INT, Location VARCHAR(255), );
Now create another table with the contact details of the customer create a table as −
CREATE TABLE CustContactDetails ( ID INT, Name VARCHAR(255), Age INT, Phone BIGINT, Address VARCHAR(255), Email VARCHAR(50) );
Following query displays the Open tables that are current in use −
SHOW OPEN TABLES WHERE In_use=1;
Output
The above query generates the following output −
Database | Table | In_use | Name_locked |
---|---|---|---|
demo | custcontactdetails | 1 | 0 |
demo | salesdetails | 1 | 0 |