SQL Syntax Conventions

This document outlines the standard syntax conventions used in Microsoft SQL Server documentation to represent SQL statements, keywords, identifiers, and other language elements.

General Conventions

SQL keywords are presented in uppercase.
User-defined identifiers (such as table names, column names, function names) are presented in sentence case.
Optional elements are enclosed in square brackets ([ ]).
Required elements are not enclosed in any special characters.
Elements that can be repeated are indicated by ellipses (...).
Alternative elements are separated by vertical bars (|) and enclosed in curly braces ({ }) to indicate a choice.

Syntax Representation

The following table details common syntax elements and their representation:

Element	Description	Example
Uppercase Keywords	SQL language keywords (e.g., `SELECT`, `FROM`, `WHERE`).	`SELECT` `column_name` `FROM` `table_name`;
Sentence Case Identifiers	User-defined names for tables, columns, views, procedures, etc.	`CustomerName`, `OrderDetails`
Square Brackets [ ]	Optional clauses or parameters.	`SELECT` `column_name` [ `AS` `alias_name` ] `FROM` `table_name`;
Ellipses ...	Indicates that an element or group of elements can be repeated.	`INSERT` `INTO` `table_name` ( `column1`, `column2`, ... ) `VALUES` ( `value1`, `value2`, ... );
Curly Braces { } with \|	Indicates a required choice between two or more options.	`CREATE` `TABLE` `table_name` ( { `column_name` `data_type` \| `CONSTRAINT` `constraint_name` `constraint_definition` } ... );
Angle Brackets < >	Placeholder for a specific value or expression.	`SELECT` * `FROM` `Products` `WHERE` `UnitPrice` > `<price_threshold>`;
Braces { } (as literals)	Literal curly braces, often used for grouping.	`SET` @`variable` = {`value1`, `value2`};

Examples of Syntax Elements

Keywords

SQL keywords are always presented in uppercase to distinguish them from identifiers.

SELECT, INSERT, UPDATE, DELETE, FROM, WHERE, GROUP BY, ORDER BY, JOIN, PRIMARY KEY, FOREIGN KEY, CONSTRAINT

Identifiers

Identifiers, such as table and column names, are usually written in sentence case. If they contain spaces or are reserved keywords, they should be enclosed in square brackets ([ ]) or double quotes (" ") depending on the database system configuration.

SELECT FirstName, LastName FROM Employees WHERE DepartmentID = 5;

Example with a reserved identifier (if not using quoting rules):

SELECT [Order] FROM OrderTable;

Optional Clauses

The ORDER BY clause is optional in a SELECT statement.

SELECT ProductName, UnitPrice
FROM Products
[ ORDER BY UnitPrice DESC ];

Choices

When specifying data types for a column, you have to choose one.

CREATE TABLE Users (
    UserID INT PRIMARY KEY,
    UserName VARCHAR(50),
    { Age INT | DateOfBirth DATE }
);

Repetitive Elements

When inserting multiple rows, you can provide multiple sets of values.

INSERT INTO Sales ( ProductID, Quantity, SaleDate )
VALUES
    ( 101, 5, '2023-10-26' ),
    ( 102, 2, '2023-10-26' ),
    ... ;

Comments

Comments in SQL can be single-line or multi-line.

-- This is a single-line comment.
SELECT COUNT(*) FROM Orders;

/* This is a multi-line
   comment that spans
   several lines. */
UPDATE Products
SET Discontinued = 1
WHERE ProductID = 70;

Adhering to these conventions ensures clarity and consistency across SQL documentation, making it easier for developers and database administrators to understand and use SQL effectively.