[New] SQL Functions (#5556)

* tech edits

* Updated front matter

* Fixed author attribution on 10 guides by same author

---------

Co-authored-by: Matthew Wildman <matt@wildman.online>

docs/contributors/doug-hayman-for-nanohertz-solutions-inc/_index.md

@@ -1,8 +1,8 @@
 ---
-title: "Doug Hayman for NanoHertz Solutions Inc."
+title: "Doug Hayman for NanoHertz Solutions Inc"
 link: "http://nhzsolutions.com/"
 email: ""
 description: "The Linode documentation library's profile page and submission listing for Doug Hayman for NanoHertz Solutions Inc."
 ---
 
-Doug Hayman for NanoHertz Solutions Inc. is an independent contributor to the Linode documentation library. Their submissions can be found listed below.
+Doug Hayman for NanoHertz Solutions is an independent contributor to the Linode documentation library. Their submissions can be found listed below.

docs/guides/databases/mysql/a-primer-on-sql-transactions/index.md

@@ -3,8 +3,8 @@ slug: a-primer-on-sql-transactions
 title: "SQL Transactions: An Introduction"
 title_meta: "A Primer on SQL Transactions"
 description: 'SQL transactions help maintain database integrity. This guide outlines some transaction benefits and how to use the delimiter, commit, and rollback syntax.'
-authors: ["Doug Hayman for NanoHertz Solutions Inc."]
-contributors: ["Doug Hayman for NanoHertz Solutions Inc."]
+authors: ["Doug Hayman for NanoHertz Solutions Inc"]
+contributors: ["Doug Hayman for NanoHertz Solutions Inc"]
 published: 2022-08-25
 keywords: ['sql transactions', 'commit transaction', 'rollback transaction', 'SQL transaction delimiter']
 tags: ['mysql', 'database']

docs/guides/databases/mysql/sql-functions/index.md

@@ -0,0 +1,288 @@
+---
+slug: sql-functions
+title: "Introduction to SQL Functions"
+description: "Learn about SQL functions and how it can be used for performing calculations on data."
+authors: ["Doug Hayman for NanoHertz Solutions Inc"]
+contributors: ["Doug Hayman for NanoHertz Solutions Inc"]
+published: 2022-06-27
+keywords: ['SQL mathematical functions', 'SQL date functions', 'SQL string functions', 'SQL conversion functions']
+tags: ['mysql']
+license: '[CC BY-ND 4.0](https://creativecommons.org/licenses/by-nd/4.0)'
+---
+
+SQL Server, MySQL server, and other commercial database systems offer a host of built-in functions that include mathematical, date, string, and conversion functions. These functions can be used for both processing and manipulating data within the server environments. These inherent functions provide valuable enhancements/extensions to the SQL language and are useful programmatic utilities that are available to a SQL developer.
+
+In this guide, we discuss SQL functions, what they are, and how they work.
+
+## SQL Mathematical Functions
+
+Most SQL dialects offer a plethora of mathematical functions as added enhancements to the SQL language. In addition to many mathematical functions, some of the more widely used include `ABS`, `COUNT`, `MIN`, `MAX`, `ROUND`, and `SUM` which are all outlined below.
+
+### ABS() function
+
+The `ABS()` function returns the absolute value of a constant or expression and returns `NULL` if the constant or expression is `NULL`.
+
+For example:
+
+    SELECT ABS(2);   /* Returns a value of "2" */
+
+    SELECT ABS(-2);  /* Returns a value of "2" */
+
+### COUNT() function
+
+The `COUNT()` function returns the number of rows that matches a specified criterion in a `Select` statement.
+
+The format of the COUNT() function is:
+
+    SELECT COUNT(ColumnName)
+    FROM   Table
+    WHERE  Criteria
+
+where `ColumnName` is the name of a column in table `Table`, and `Criteria` is a condition based on which `COUNT()` returns the number of rows matched.
+
+For example:
+
+    SELECT COUNT(EmployeeName)
+    FROM   Employees
+    WHERE  Salary > 100000;    /* Returns the count of employees
+                                with salary > $100k */
+
+### MIN() and MAX() function
+
+The `MIN()` function returns the minimum value of a selected column, whereas the `MAX()` function returns the maximum value of a selected column.
+
+For example:
+
+    SELECT MAX(Salary)
+    FROM   Employees;  /* Returns the highest salary of all employees
+                       in table Employees */
+
+    SELECT MIN(Salary)
+    FROM   Employees;  /* Returns the lowest salary of all employees
+                       in table Employees */
+
+### ROUND() function
+
+The `ROUND()` function rounds a number to a specified number of decimal places.
+
+The format of the `ROUND()` function is:
+
+    ROUND( Number, DecimalPlaces);  /* Round Number to # of DecimalPlace */
+
+For example:
+
+    SELECT ROUND (346.315, 2);      /* Returns a value of 346.32 */
+
+    SELECT ROUND (346.314, 2);      /* Returns a value of 346.31 */
+
+    SELECT ROUND (346.27863, 3);    /* Returns a value of 346.279 */
+
+### SUM() function
+
+The `SUM()` function calculates the sum of a set of values.
+
+For example:
+
+    SELECT SUM(Quantity)
+    FROM OrderDetails;     /* Returns the Sum of Column Quantity
+                            from the OrderDetails Table */
+
+## SQL Date Functions
+
+Most SQL dialects offer several date functions that are added enhancements to the SQL language. Although the names of date functions differ across the different database server implementations, their functionality is identical. In SQL Server, some of the more popular date functions include `GETDATE`, `DATEPART`, `DATEADD`, `DATEDIFF`, and `CONVERT`, which are all outlined below.
+
+### GETDATE() function
+
+The `GETDATE()` function is a SQL Server function that returns the current date and time. Its MySQL equivalent is the `NOW()` function.
+
+    SELECT GETDATE();    /* Returns this system date.
+                          As an example,'2022-03-19 11:22.04' */
+
+In the following example, any time a record is inserted into the `Orders` table, the current date/time is inserted into the `OrderDate` column. This is because its default is defined by the `GETDATE()` function.
+
+     CREATE TABLE Orders (
+        OrderId       INT           NOT NULL,
+        ProductName   VARCHAR(25)   NOT NULL,
+        OrderDate     DATETIME NOT  NULL DEFAULT GETDATE()
+    );
+
+### DATEPART() function
+
+The `DATEPART()` function returns a specific portion of a date/time string, based on a unit specification. The unit specification can be any portion of the date/time string including Year, Month, Day, Hour, Minute, Seconds, etc. The MySQL equivalent is the `EXTRACT()` function.
+
+The format of the `DATEPART()` function is:
+
+    DATEPART (unit, date string)
+
+For example, using the `Orders` table specified above, we can retrieve specific units (year, month, and day) of the `OrderDate` column for `OrderId` 7, as shown below:
+
+    SELECT   DATEPART(yyyy, OrderDate),
+             DATEPART(mm, OrderDate),
+             DATEPART(dd, OrderDate)
+    FROM Orders
+    WHERE OrderId = 7;
+
+### DATEADD() function
+
+The `DATEADD()` function adds (or subtracts using negative units) a specified time interval (based on a specified unit) from a date, where the unit specification can be in Years, Months, Days, Hours, Minutes, Seconds, etc. The MySQL equivalent functions are `DATE_ADD()` and `DATE_SUB()`.
+
+The format of the `DATEADD()` function is:
+
+    DATEADD(unit, number, date)
+
+For example, following is the SQL code to calculate 30 days beyond the `OrderDate` in the `Orders` table, for `OrderId` 7:
+
+    SELECT DATEADD(day, 30, OrderDate)
+    FROM Orders
+    WHERE OrderId = 7;
+
+### DATEDIFF() function
+
+The `DATEDIFF()` function, similarly named in MySQL, returns the time between two dates. The unit specification for the difference can again be expressed in Years, Months, Days, Hours, Minutes, Seconds, etc.
+
+The format of the `DATEDIFF()` function is:
+
+    DATEDIFF(unit, startdate, enddate)
+
+Consider the `Orders` table example above. For `OrderId` 7, to calculate the number of days that have elapsed between Today (from `GETDATE()`), and the `OrderDate` column value, the SQL code would be:
+
+    SELECT DATEDIFF(day, GETDATE(), OrderDate)
+    FROM Orders
+    WHERE  OrderId=7;
+
+### CONVERT() function
+
+The `CONVERT()` function can be used to display date/time data in different formats. The MySQL equivalent function is the `DATE_FORMAT()` function.
+
+The format of the `CONVERT()` function is:
+
+    CONVERT(data_type(length), expression, style)
+
+where `style` can be a myriad of numeric output formats (see SQL Server documentation for an [exhaustive list](https://docs.microsoft.com/en-us/sql/t-sql/functions/format-transact-sql?view=sql-server-ver16)).
+
+For example:
+
+    SELECT GETDATE();    /* Returns this system date.
+                            For example, 2022-03-19 11:22.04 */
+
+    SELECT CONVERT(VARCHAR(10), GETDATE(), 10);
+    /* Returns ‘03-19-22’, since style "10" equates to "mm-dd-yy" */
+
+## SQL String Functions
+
+Most SQL dialects offer a number of string manipulation functions which are added enhancements to the SQL language. Some of the more prominent SQL Server string functions include `CHARINDEX`, `CONCAT`, `FORMAT`, `LEFT`, `LEN`, `RIGHT`, `TRIM`, and `SUBSTRING`. If the string function names (described below) in MySQL differ, their counterpart name is specified.
+
+### CHARINDEX() function
+
+The `CHARINDEX()` function searches for a substring in a string and returns the starting numeric position of the specified substring. If the substring is not found within the string, this function returns a value of "0". The MySQL equivalent function is named `INSTR`.
+
+The format of the `CHARINDEX()` function is:
+
+    CHARINDEX(substring, string, start)
+
+For example:
+
+    SELECT CHARINDEX('b’, 'Zebra');   /* Returns a value of ‘3’ */
+
+    SELECT CHARINDEX('y’, 'Zebra');   /* Returns a value of ‘0’ */
+
+### CONCAT() function
+
+The `CONCAT()` function adds two or more strings together.
+
+The format of the `CONCAT()` function is:
+
+     CONCAT(string1, string2, ...., stringN)
+
+For example:
+
+     SELECT CONCAT('Today is ', 'Sunday');   /* Returns the string:
+                                               'Today is Sunday' */
+
+### FORMAT() function
+
+The `FORMAT()` function formats a value with the specified format. It is typically used to format date/time values and numeric values.
+
+The format of the `FORMAT()` function is:
+
+    FORMAT(value, format)
+
+For example:
+
+    SELECT FORMAT(111223333, '##-##-#####'); /* Returns the string '111-22-3333' */
+
+### LEFT() function
+
+The `LEFT()` function returns a substring with a specified number of characters from a string (starting from the left; that is position 1).
+
+The format of the `LEFT()` functions is:
+
+     LEFT(string, NumberOfChars)
+
+For example:
+
+     SELECT LEFT('Johanson', 5); /* Returns a substring of ‘Johan’ */
+
+### LEN() function
+
+The function `LEN()` returns the length of a string. The Mysql equivalent function is named `CHAR_LENGTH`.
+
+The format of the `LEN()` function is:
+
+    LEN(string)
+
+For example:
+
+    SELECT LEN('My dog is named Lily');  /* Returns a value of 20 */
+
+### RIGHT() function
+
+The `RIGHT()` function returns a substring with a specified number of characters from a string (starting from the right).
+
+The format of the `RIGHT()` functions is:
+
+    RIGHT(string, NumberOfChars)
+
+For example:
+
+    SELECT RIGHT('Johanson', 5);    /* Returns a substring of 'anson' */
+
+### TRIM() function
+
+The `TRIM()` function removes both leading and trailing spaces from a string.
+
+The format of the `TRIM()` function is:
+
+    SELECT TRIM(string)
+
+For example:
+
+    SELECT TRIM(' This is a string `); /* Returns the string This is a string' */
+
+### SUBSTRING() function
+
+The `SUBSTRING()` function returns a substring of characters from a string, given a starting position and a specified length of the required substring.
+
+The format of the `SUBSTRING()` function is:
+
+    SUBSTRING(string, start, length)
+
+For example:
+
+    SELECT SUBSTRING('Mr. Jones', 5, 5);   /* Returns a substring of ‘Jones’ */
+
+## SQL Conversion Functions
+
+In addition to assisting date/time columns/values from being converted to different display formats (noted in the SQL Date functions section above), the `CONVERT()` function can also be used to convert a value of any type into a different specified datatype.
+
+In this context, the format of the `CONVERT()` function is:
+
+    SELECT CONVERT(datatype, value);
+
+For example:
+
+    SELECT CONVERT(VARCHAR(20), 12345.34); /* Returns a string of ‘12345.34’ */
+
+## Conclusion
+
+The use of mathematical, date/time, string, and conversion functions offers many built-in facilities that help augment the SQL language. These powerful functions can be used for both processing and manipulating data in a database server environment.

docs/guides/databases/sql-syntax/sql-commands/index.md

@@ -3,8 +3,8 @@ slug: sql-commands
 title: "Introduction to SQL Commands"
 title_meta: "SQL Commands: Getting Started"
 description: 'SQL commands can be used across relational database systems like MySQL and PostgreSQL. Learn the fundamental SQL commands used to insert and modify data in a SQL table.'
-authors: ["Doug Hayman for NanoHertz Solutions Inc."]
-contributors: ["Doug Hayman for NanoHertz Solutions Inc."]
+authors: ["Doug Hayman for NanoHertz Solutions Inc"]
+contributors: ["Doug Hayman for NanoHertz Solutions Inc"]
 published: 2022-03-04
 keywords: ['create table', 'alter table', 'drop table', 'ddl commands']
 tags: ['MySQL']

docs/guides/databases/sql-syntax/sql-data-types/index.md

@@ -3,8 +3,8 @@ slug: sql-data-types
 title: "Introduction to SQL Data Types"
 title_meta: "SQL Data Types"
 description: 'SQL supports various data types including Binary, Numeric, and Character data types. This guide explains each data type''s storage requirements, syntax, and provides examples.'
-authors: ["Doug Hayman for NanoHertz Solutions Inc."]
-contributors: ["Doug Hayman for NanoHertz Solutions Inc."]
+authors: ["Doug Hayman for NanoHertz Solutions Inc"]
+contributors: ["Doug Hayman for NanoHertz Solutions Inc"]
 published: 2022-03-11
 keywords: ['binary data type', 'numeric data type', 'character data type', 'date time data type']
 tags: ['MySQL', 'PostgreSQL']

docs/guides/databases/sql-syntax/sql-grouping-and-totaling/index.md

@@ -3,8 +3,8 @@ slug: sql-grouping-and-totaling
 title: "Introduction to SQL Grouping and Totaling"
 title_meta: "SQL Grouping and Totaling"
 description: "SQL aggregate functions calculate a set of values by using grouping and totaling. This guide uses various examples to demonstrate how to calculate values using the Where and Having clauses."
-authors: ["Doug Hayman for NanoHertz Solutions Inc."]
-contributors: ["Doug Hayman for NanoHertz Solutions Inc."]
+authors: ["Doug Hayman for NanoHertz Solutions Inc"]
+contributors: ["Doug Hayman for NanoHertz Solutions Inc"]
 published: 2022-03-18
 keywords: ['aggregate functions', 'group functions', 'where clause', 'having clause']
 tags: ['MySQL', 'PostgreSQL']

docs/guides/databases/sql-syntax/sql-indexes/index.md

@@ -3,8 +3,8 @@ slug: sql-indexes
 title: "An Introduction to SQL Indexes"
 title_meta: "How to Use SQL Indexes"
 description: 'SQL indexes are used to improve a database''s performance during query lookups. This guide discusses unique indexes, primary keys, and composite primary keys.'
-authors: ["Doug Hayman for NanoHertz Solutions Inc."]
-contributors: ["Doug Hayman for NanoHertz Solutions Inc."]
+authors: ["Doug Hayman for NanoHertz Solutions Inc"]
+contributors: ["Doug Hayman for NanoHertz Solutions Inc"]
 published: 2022-03-25
 keywords: ['database index', 'non-unique indexes', 'database performance']
 tags: ['MySQL']

docs/guides/databases/sql-syntax/sql-joins/index.md

@@ -3,8 +3,8 @@ slug: sql-joins
 title: "Introduction to SQL Joins"
 title_meta: "SQL Joins"
 description: 'SQL Joins are used to compare and select rows from tables. This guide discusses Cross Joins, Inner Joins, Left Joins, Right Joins, and Full Joins and provides examples for each SQL Join.'
-authors: ["Doug Hayman for NanoHertz Solutions Inc."]
-contributors: ["Doug Hayman for NanoHertz Solutions Inc."]
+authors: ["Doug Hayman for NanoHertz Solutions Inc"]
+contributors: ["Doug Hayman for NanoHertz Solutions Inc"]
 published: 2022-03-11
 keywords: ['SQL Joins', 'Cross Joins', 'Left Join', 'Right Join', 'Full Join']
 tags: ['mysql', 'postgresql', 'database']

docs/guides/databases/sql-syntax/sql-security/index.md

@@ -3,8 +3,8 @@ slug: sql-security
 title: "SQL Database Security: User Management"
 title_meta: "SQL Security and User Management"
 description: 'SQL database security relies on user management, permissions, groups, and roles. This guide discusses each of these aspects of SQL database security with examples.'
-authors: ["Doug Hayman for NanoHertz Solutions Inc."]
-contributors: ["Doug Hayman for NanoHertz Solutions Inc."]
+authors: ["Doug Hayman for NanoHertz Solutions Inc"]
+contributors: ["Doug Hayman for NanoHertz Solutions Inc"]
 published: 2022-05-20
 keywords: ['groups', 'roles', 'permissions', 'grant permission', 'revoke permission']
 tags: ['MySQL']

docs/guides/databases/sql-syntax/sql-server-security-part-2/index.md

@@ -3,8 +3,8 @@ slug: sql-server-security-part-2
 title: "Part 2: SQL Server Security Best Practices"
 title_meta: "SQL Server Security Best Practices, Part 2"
 description: 'Learn about the SQL Server security best practices and guidelines to keep your server and data safe. For example, selecting a SQL Server authentication mode.'
-authors: ["Doug Hayman for NanoHertz Solutions Inc."]
-contributors: ["Doug Hayman for NanoHertz Solutions Inc."]
+authors: ["Doug Hayman for NanoHertz Solutions Inc"]
+contributors: ["Doug Hayman for NanoHertz Solutions Inc"]
 published: 2022-08-12
 keywords: ['SQL server authentication', 'Restrict SQL traffic', 'SQL Server Patches', 'Backups', 'Auditing']
 tags: ['database']