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General: Prevent arbitrary precision arithmetic

Demand Some simple decimal calculations like 4.6 * 100 may lead in irregularities when dealing with numbers. Description During arithmetic operations like addition, subtraction, multiplication, and division, the numbers are manipulated according to the rules defined by the IEEE 754 standard. However, due to the finite precision of the representation, rounding errors may occur, leading to small discrepancies between the expected and actual results of computations.  To prevent it we may use some libraries to prevent the problem. In Javascript and Typescript we have the BigNumbers library (and others). PHP has a built-in library for arbitrary-precision arithmetic called BCMath (Binary Calculator). Wich I reccomend. It provides functions to perform mathematical operations on numbers with arbitrary precision, including addition, subtraction, multiplication, division, and more. Examples PHP Sample 1: php > var_dump(floor((10*0.91597) * 1000000)/1000000); 2: float(9.159699) 3: php ...
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SQL: Unique Key constraint name convention

  Demand ALWAYS name unique key as "uq_{IndexName}" Description We use this convention to easily identify the source of the failure, especially in schema updates. When creating a CONSTRAINT we create its name starting with the string "uq", followed by the full name of the source table column used to build the index. Both separated by "_" (underline). Examples 1: CREATE TABLE customers ( 2:     id INT NOT NULL, 3:   name VARCHAR(100) NOT NULL, 4:    user_id INT NULL COMMENT 'if the customer have a system login it will be refernced here', 5:      PRIMARY KEY (id), 6: UNIQUE KEY `uq_user_id` (`user_id`), 6:      CONSTRAINT `fk_customers_user_id_users_user_id` 7:           FOREIGN KEY (`user_id`) 8:      REFERENCES `users` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION 9: ); Examples Explanation Here the  uq_user_id  is used to build a unique key...
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SQL: Primary Key constraint name convention

Demand ALWAYS name forein keys constraints as "fk_{LocalTableName}_{LocalColumnName}_{DestinationTableName}_{DestinationFieldName}" Description We use this convention to easily identify the source of the failure, especially in schema updates. When creating a CONSTRAINT we create its name starting with the string "fk", followed by the full name of the source table, also called local table or child table, followed by the name of the column used in the source table to store the value to be searched for later in the target table, the name of the target table and finally the name of the field in the target table. All separated by "_" (underline). Examples 1: CREATE TABLE customers ( 2:     id INT NOT NULL, 3:   name VARCHAR(100) NOT NULL, 4:    user_id INT NULL COMMENT 'if the customer have a system login it will be refernced here', 5:      PRIMARY KEY (id), 6:      CONSTRAINT `fk_customers_user_id_users_user_id` 7:...
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SQL: Naming external identification code fields at database.

Demand Use "id_{context}" to name fields of external identification codes and "{context}_id" to internal ones. Description When creating a column in a table that reference an id (identification code) of a table located at the database you are dealing it should be named as "{Table Name}_id". When creating a column in a table that reference an id of a context external to the database you are dealing with  it should be named as "id_{Context Name}". Examples 1: CREATE TABLE customer ( 2:     id INT NOT NULL, 3:   name VARCHAR(100) NOT NULL, 4:     id_ssn COMMENT ' the United States, the Social Security number', 5:    user_id INT NULL COMMENT 'if the customer have a system login it will be refernced here', 6:      PRIMARY KEY (id), 7:     UNIQUE `uq_ssn` (`ssn`), 8:      CONSTRAINT `fk_customers_user_id_users_user_id` 9:           FOREIGN KEY (`user...
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PHP: Always use an index to add a values to an array

  Demand Always identify the array index when manipulating the array directly Description Whenever you are adding a new item to the array you must add an index so that php does not need to recalculate the size of the array to identify in which position the new content will be added. Examples 1: # Bad code: 2: do { 3: $array[] = $newItem; 4: } while(!feof($fp)); 5: 6: # Good code 7: $array = []; 8: $index = 0; 9: do { 10: $array[$index++] = $newItem; 11: } while(!feof($fp)); Examples Explanation When instantiating a new item in an array in the "bad example" php will identify that you expect the item to be added to the end of the array, since array is a primitive type and has no attributes php always needs to call a calculation function to identify the current size of the array before trying to add a new item to the end of it. By monitoring the growth of the array in an external variable and automatically reference which position will...
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SQL: Never uses LIKE unless stricted necessary.

Demand MUST use "=" (equals sign) instead "LIKE" (like command) whenever "%" (percent sign) is NOT necessary Description In MySQL, the " LIKE " operator behaves similarly to " = " (equals sign) when the " % " (percent sign) wildcard is not utilized. Employing " LIKE " in most of the modern SGDBs (e.q. MySQL) results in the use of a more complex query structures. The examples below illustrate this. The first query does not use the " % " modifier and is compared to the second, which does. Both provide the same search structure. Contrasting these with the last query, which uses only " = ", results in a simpler search structure and all have the same output result. Therefore, if the " % " modifier is not being used in the search, it's preferable to utilize " = " for simpler and more efficient query execution. Examples 1: explain SELECT COUNT(1) FROM users WHERE `username` lik...
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