The modern MySQL database is not critical to the number of records. It is rarely necessary to control overstepping the limits of the number of rows.
Meanwhile, there are many problems when the database structure itself is essential data and the use of tables should be controlled in the number of records in general and the specific content in particular.
Function Syntax and Usage Example
The MySQL count function is used directly in the database query. A function has only two main forms of application: all records or only specific ones. There is only one significant factor - the selected row by field, which is included in the expression count (), should not be NULL.
In the above example, the MySQL count function is used unconditionally. It should be noted that the use of count (*) is a reference to all records in the table and it does not matter at all that some records may have a NULL value. A query containing count (*) will always return the entire number of records contained in the table.
The developer can provide the meaning of the expression:
But it will have more visual significance than practical.
PHP & MySQL Security: count () - in practice
Security issues are the focus of the efforts of the most skilled cohort of developers. But to this day there are gaps, attacks occur, valuable information is lost or stolen.
There are only two of the most reliable and secure barriers to any attacker:
The first barrier is the most reinforced concrete. You can speculate about anything, but if you do not know where, why and how, then there will never be an effect. You always need a door to open, a key to it, and a good reason to do it.
In the context of the second solution, the functions count (*) and count (...) MySQL are examples of ideal protection. Most importantly, these functions are unconditional and primitive . They will be executed under any state of things, the main thing is that the database itself works and a connection is established with it.
By constructing a security table so that each input / output of a company employee is marked as NULL or not NULL, you can control all deviations that occur during the working hours of the day. Naturally, weekends, holidays, and non-working hours should reset all security table entries to NULL.
Even with such primitive logic, you can notice and prevent any unforeseen intrusion in the simplest way, without much cost. The simpler and quieter the defense, the more difficult it is to build an invasion.
Conditions and special cases
The example below uses the condition that not all table entries participate in the MySQL count operation.
The result of the execution of all queries meets the condition. In this case, the use of the request:
- select param1 + param2 + param3 from `ex_count` where count (*)
equivalent to request
- select count (*) from `ex_count` where (param1 + param2 + param3)> 0.
The MySQL count function allows for a variety of uses, including in nested queries. However, one should always take into account: simplicity is the key to success. The function of counting the number of records by certain conditions is too simple, but its application should not be made too complicated.
There is a sure key to the strongest defense - “case” - which in transliteration into a simple language means “regularity”. So for the complex application of simple operations like count MySQL, a different inquiring mind of the developer may hang such functionality that in an unforeseen situation will not work at all as it was intended.