You can setup them in /etc/my.cnf (CentOS 7)
vi /etc/my.cnf
Append config directives as follows:
query_cache_size = 268435456 query_cache_type=1 query_cache_limit=1048576
In above example the maximum size of individual query results that can be cached set to 1048576 using query_cache_limit system variable. Memory size in Kb.
Restart the mysql service.
service mysqld restart
Similar in concept to templates – contain compiled code used to run common sql operations
o Advantages:
Query only parsed once, but allows for multiple executions, with same or different parameters (performance consideration)
Related parameters do not need to be quoted (security consideration)
o Only feature pdo will emulate for adapters that do not support prepared statements
Unbuffered MySQL queries execute the query and then return a resource while the data is still waiting on the MySQL server for being fetched. This uses less memory on the PHP-side, but can increase the load on the server. Unless the full result set was fetched from the server no further queries can be sent over the same connection. Unbuffered queries can also be referred to as “use result”.
A cursor can’t be used by itself in MySQL. It is an essential component in stored procedures. I would be inclined to treat a cursor as a “pointer” in C/C++, or an iterator in PHP’s foreach statement.
With cursors, we can traverse a dataset and manipulate each record to accomplish certain tasks. When such an operation on a record can also be done in the PHP layer, it saves data transfer amounts as we can just return the processed aggregation/statistical result back to the PHP layer (thus eliminating the select – foreach – manipulation process at the client side).
Since a cursor is implemented in a stored procedure, it has all the benefits (and limitations) of an SP (access control, pre-compiled, hard to debug, etc).
MySQL supports cursors inside stored programs. The syntax is as in embedded SQL. Cursors have these properties:
Asensitive: The server may or may not make a copy of its result table
Read only: Not updatable
Nonscrollable: Can be traversed only in one direction and cannot skip rows
Cursor declarations must appear before handler declarations and after variable and condition declarations.
phpMyAdmin is a free and open source tool written in PHP intended to handle the administration of MySQL with the use of a web browser. It can perform various tasks such as creating, modifying or deleting databases, tables, fields or rows; executing SQL statements; or managing users and permissions.
Install phpmyadmin
1) Execute sudo apt-get install phpmyadmin
2) Edit the file /etc/apache2/apache2.conf. and include the line Include /etc/phpmyadmin/apache.conf
3) Restart Apache sudo /etc/init.d/apache2 reload
Features
A SET is a string object that can have zero or more values, each of which must be chosen from a list of permitted values specified when the table is created. SET column values that consist of multiple set members are specified with members separated by commas (“,”). A consequence of this is that SET member values should not themselves contain commas.
Example
mysql> CREATE TABLE myset (col SET(‘a’, ‘b’, ‘c’, ‘d’));
Query OK, 0 rows affected (0.43 sec)
mysql> select * from myset;
Empty set (0.20 sec)
mysql> insert into myset value(‘p’);
Query OK, 1 row affected, 1 warning (0.23 sec)
mysql> select * from myset;
+——+
| col |
+——+
| |
+——+
1 row in set (0.10 sec)
mysql> insert into myset value(‘a’);
Query OK, 1 row affected (0.18 sec)
mysql> select * from myset;
+——+
| col |
+——+
| |
| a |
+——+
2 rows in set (0.00 sec)
mysql> insert into myset value(‘p,a’);
Query OK, 1 row affected, 1 warning (0.07 sec)
mysql> select * from myset;
+——+
| col |
+——+
| |
| a |
| a |
+——+
3 rows in set (0.00 sec)
Following are the differences between CHAR and VARCHAR:
