Mysql temporary table usage

We often use Mysql temporary tables. The following describes the usage of Mysql temporary tables for your reference. If you are interested in this, take a look.

When you work on a very large table, you may occasionally need to run many queries to obtain a small subset of a large amount of data, instead of running these queries on the entire table, instead, MySQL can find a few required records each time, and it may be faster to select a temporary table, and then run the query on these tables.

It is easy to CREATE a temporary table and add the TEMPORARY keyword to the normal create table statement:

 
 

  
  
CREATE TEMPORARY TABLE tmp_table (     
  
  
name VARCHAR(10) NOT NULL,     
  
  
value INTEGER NOT NULL     
  
  
)     
  
  
 
  
  
CREATE TEMPORARY TABLE tmp_table (  
  
  
name VARCHAR(10) NOT NULL,  
  
  
value INTEGER NOT NULL  
  
  
)  
  
  
 
 
 

Temporary tables will exist during your connection to MySQL. When you disconnect, MySQL automatically deletes the table and releases the space used. Of course, you can delete the table and release the space when it is still connected.

Drop table tmp_table

If the table named tmp_table already exists in the Database when you create a temporary table named tmp_table, it is necessary to shield the temporary table from hiding it.) Non-temporary table tmp_table.

If you declare that the Mysql temporary table is a HEAP table, MySQL also allows you to specify to create it in memory:

 
 

  
  
CREATE TEMPORARY TABLE tmp_table (     
  
  
name VARCHAR(10) NOT NULL,     
  
  
value INTEGER NOT NULL     
  
  
) TYPE = HEAP     
  
  
 
  
  
CREATE TEMPORARY TABLE tmp_table (  
  
  
name VARCHAR(10) NOT NULL,  
  
  
value INTEGER NOT NULL  
  
  
) TYPE = HEAP 
  
  
 
 
 

Because the HEAP table is stored in the memory, you may query it faster than the temporary table on the disk. However, HEAP tables are somewhat different from general tables and have their own restrictions. For more information, see the MySQL reference manual.

/*************************************** **************************************** *************/

1. After a temporary table is disconnected from mysql, the system will automatically delete the data in the temporary table. However, this is only the table created using the following statement:
1) define Fields

 
 

  
  
CREATE TEMPORARY TABLE tmp_table (   
  
  
    name VARCHAR(10) NOT NULL,   
  
  
    value INTEGER NOT NULL   
  
  
)  
 
 

2) directly import the query results to the temporary table

 
 

  
  
CREATE TEMPORARY TABLE tmp_table SELECT * FROM table_name  
 
 

2. In addition, mysql allows you to directly create temporary tables in the memory, because all the speed in the memory will be fast, and the syntax is as follows:

 
 

  
  
CREATE TEMPORARY TABLE tmp_table (   
  
  
     name VARCHAR(10) NOT NULL,   
  
  
     value INTEGER NOT NULL   
  
  
  ) TYPE = HEAP   
 
 

3. From the analysis above, we can see that the data in the temporary table will be cleared, and the data will be automatically cleared when you disconnect the connection, however, it is impossible for your program to connect to the database every time an SQL statement is released. (if this is the case, there will be issues you are worried about. If not, there will be no problems ), because data is cleared only when the database connection is disconnected, the system will not automatically clear the temporary table data if multiple SQL statements are released in a database connection.
 

 

MySQL Stored Procedure for table splitting

Detailed description of MySQL Data Table types

Implementation of MySQL fuzzy query with multiple fields in a single table

Set of MySQL Fields

Add and delete fields in MySQL