The code rule "@@IDENTITY should not be used" states that the global variable @@IDENTITY should not be used in SQL Server code. This variable is often used to retrieve the last identity value generated in the current session, but it can be unreliable and lead to unexpected results. Instead, the SCOPE_IDENTITY() function should be used to retrieve the last identity value generated in the current scope.

The rule "All branches in a conditional structure should not have exactly the same implementation" states that when a conditional structure is used in SQL Server code, the branches should not have identical implementations. This means that each branch should have a unique implementation that is tailored to the specific conditions of that branch. This helps to ensure that the code is efficient and that it produces the desired results. Additionally, this rule helps to prevent potential errors or unexpected behavior that could occur if the same implementation were used for all branches.

The "CASE expressions should not have too many WHEN clauses" rule states that when using CASE expressions in SQL Server, the number of WHEN clauses should be limited to improve readability and maintainability of the code. Having too many WHEN clauses can make the code difficult to read and understand, and can also lead to potential performance issues. This rule encourages developers to use simpler alternatives such as IF/ELSE or WHILE loops when multiple WHEN clauses are needed. Additionally, it is recommended to use meaningful names for each WHEN clause to make the code easier to read and maintain.

This rule states that when using the COALESCE, IIF, and CASE functions in SQL Server, the input expressions should not contain subqueries. Subqueries should not be used because they can cause performance issues, as well as make the code more difficult to read and maintain. Instead, use a simple expression or variable.

The "Collapsible if statements should be merged" code rule states that when multiple if statements are logically connected, they should be merged into a single if statement to improve readability and maintainability of the code. This helps to reduce the complexity of the code and make it easier to understand what the code is doing. Additionally, merging the if statements can help to reduce the number of lines of code, making it easier to debug and maintain.

This rule states that when using the ORDER BY clause in SQL Server, column names should be used instead of column numbers. This ensures that the ordering of the results is based on the columns that are specified, and not on the order of the columns in the table.

For example, if you wanted to order a table by the columns "FirstName" and "LastName", you should use the following code:

ORDER BY FirstName, LastName

Instead of using the column numbers, which may change in the future, this rule ensures that the ordering of the results is always based on the specified columns.

This SQL Server code rule states that when using a SELECT statement, the columns that are to be read should be explicitly defined. This helps to ensure that only the data that is required is read, and that the query is more efficient. Additionally, it ensures that the query is more readable, as the columns that are being read are clearly defined.

The SqlServer code rule "Deprecated features should not be used" states that any deprecated features of the SqlServer platform should not be used in code. Deprecated features are features that have been superseded by newer versions or features, and are no longer supported by the platform. Using deprecated features can lead to security vulnerabilities, performance issues, and compatibility problems, so it is important to avoid using them in code. It is also important to ensure that any code written is up to date with the latest version of SqlServer, as new features may be available that can improve the code's performance or security.

The rule "Deprecated system tables and views should not be used" states that any system tables or views that have been marked as deprecated, or are no longer supported, should not be used by developers when writing SQL Server code. This rule is important because deprecated system tables and views can contain outdated or inaccurate data, and using them in code can lead to unexpected results or errors. Additionally, using deprecated system tables and views can also cause performance issues if the code is not optimized properly.

The "Duplicate values should not be passed as arguments" SQL Server code rule states that when passing arguments to a stored procedure or function, any duplicate values should not be included. This is to avoid any potential issues with the code, such as an unexpected result or an error. By not including duplicate values, the code will be more reliable and efficient. In some cases, it may also be necessary to check the data type of the argument to ensure that they are compatible with the data type of the parameter. This code rule helps to ensure that the code is robust and reliable.

This rule states that files should not contain an excessive amount of code. This is to ensure that files are easier to read and understand. It is also important to keep code organized and manageable. Too much code can lead to confusion and difficulty in debugging and maintaining the code. This rule helps to keep code organized and maintainable. It is important to keep the code as concise as possible and to split up large files into smaller, more manageable chunks. This will ensure that the code is easier to read and understand.

The "Function and Procedure Names Should Comply with a Naming Convention" rule states that all functions and procedures within a SQL Server database should be named according to a predetermined naming convention. This naming convention should be consistent across all databases and should be used to make it easier for developers and administrators to identify the purpose of a particular function or procedure. This naming convention should also be documented and used to ensure that all functions and procedures are consistently named.

The code rule "Functions and procedures should not have too many parameters" states that functions and procedures should be kept as simple as possible, with a limited number of parameters. Having too many parameters can make the code difficult to read, understand, and maintain. It can also lead to increased complexity and a greater chance of errors. When designing functions and procedures, it is important to keep the number of parameters to a minimum, and to use descriptive names for each parameter. This will make the code easier to read and maintain, and will reduce the chances of errors.

The SQL Server code rule "Functions and stored procedures should not have too many lines of code" is a best practice for developers to follow when creating functions and stored procedures. This rule is designed to help maintain code readability and reduce the complexity of the code. It is important to keep the code concise and easy to understand, as too many lines of code can lead to confusion and difficulty in debugging. Additionally, too much code can lead to an increase in the amount of time it takes to execute the code. By following this rule, developers can ensure their code is efficient and maintainable.

The GOTO statements should not be used rule states that GOTO statements should not be used when writing SQL Server code. GOTO statements are a type of unconditional jump which can make code difficult to read and maintain. They should be avoided in favor of more structured programming techniques, such as using IF-ELSE statements. Using GOTO statements can also lead to unintended results, as the code may not execute as intended. This rule encourages developers to use more structured programming techniques to ensure that code is more readable and maintainable.

This rule states that when using a binary operator (such as an equals sign or a less than sign) the same expression should not be used on both sides of the operator. For example, in the following statement:

x = x

The expression "x" is used on both sides of the equals sign, which is not allowed according to this rule. Instead, the statement should be written as:

x = 5

or some other expression that is not the same on both sides of the equals sign.

The "Jump statements should not be followed by dead code" rule states that any statement that causes the execution to jump to another part of the code, such as a loop or an IF statement, should not be followed by any code that will not be executed. This is because such code is unnecessary and can lead to confusion and errors when debugging or maintaining the code. This rule helps ensure that the code is clean and efficient, and that any code that is written is actually being used.

The rule "LIKE clauses should not start with wildcard characters" means that when using the LIKE clause in SQL Server, wildcard characters such as % and _ should not be used as the first character in the clause. This is because wildcards are used to match any character or string of characters, so starting with one will cause the query to return too many results. This can cause performance issues and make it difficult to interpret the results.

The "Loops with at most one iteration should be refactored" code rule for SQL Server suggests that any loop that has a single iteration should be refactored into a simpler code structure. This is because, in most cases, a loop with a single iteration can be replaced with a simpler code structure that can be more easily understood and maintained. By refactoring the code, it can improve the readability and maintainability of the code and reduce the risk of errors. Additionally, it can improve the performance of the code by reducing the amount of unnecessary looping operations.

The Multiline blocks should be enclosed in BEGIN...END blocks rule states that any SQL Server code containing multiple lines of code should be enclosed with a BEGIN...END block. This is to ensure that all lines of code are executed together as a single unit and that any errors that occur are handled in the same way. It also helps to make code easier to read and debug.

The SQL Server code rule "NULL should not be compared directly" means that when comparing two values, an explicit comparison operator should be used instead of just comparing the values directly. This is because a direct comparison of two NULL values will always return true, which may not be the desired result. Instead, an explicit comparison operator should be used to ensure the comparison is done correctly. For example, instead of writing "IF x = NULL", the code should be written as "IF x IS NULL".

The "Output parameters should be assigned" rule states that any output parameters declared in a SQL Server stored procedure should be assigned a value before the procedure is executed. This ensures that the output parameters are not left unassigned, which can lead to unexpected behavior and errors. Additionally, this rule helps to make the code more readable and maintainable by making it clear which output parameters are being used and what values they should be assigned.

The "Queries should not join too many tables" code rule states that when writing SQL queries, it is important to limit the number of tables that are joined in the query. Joining too many tables can lead to complex queries that are difficult to read, debug, and maintain. Additionally, joining too many tables can lead to decreased performance, as the query optimizer must process more data to return the desired result set. Therefore, it is recommended to limit the number of tables joined in a query to improve readability and performance.

The SQL Server code rule "Queries that use TOP should have an ORDER BY" requires that when using the TOP clause in a query, an ORDER BY clause must also be included. This ensures that the results of the query are in a predictable order. Without an ORDER BY clause, the order of the results is not guaranteed. This rule is in place to ensure that the results of the query are consistent and predictable.

The "Redundant pairs of parentheses should be removed" SQL Server code rule aims to reduce unnecessary complexity in code and improve readability by removing redundant parentheses. This rule applies to all SQL Server code, including SELECT, INSERT, UPDATE, and DELETE statements. Redundant parentheses are those that are not required to determine the order of operations in the code. Removing these parentheses can help make the code easier to read and understand, as well as reducing the amount of code needed to accomplish a given task. Additionally, removing redundant parentheses can help improve the performance of the code by reducing the amount of time needed to parse the code.

The "Related IF/ELSE IF statements and WHEN clauses in a CASE should not have the same condition" SQL Server code rule states that when using IF/ELSE IF statements and WHEN clauses in a CASE statement, the conditions should be different. This ensures that the correct logic is being used and that the code is not redundant. If the same condition is used for multiple IF/ELSE IF statements or WHEN clauses, then the code will not be as efficient as it could be and could lead to unexpected results. It is important to ensure that the conditions are different for each IF/ELSE IF statement and WHEN clause in order to ensure that the code is efficient and that the results are as expected.

The "Statements should be on separate lines" code rule for SQL Server means that each individual statement should be written on its own line. This helps to improve readability and maintainability of code. It also helps to ensure that any changes to the code are easier to identify and modify, as each statement is clearly separated from the other statements. This rule helps to ensure that SQL code is easier to read and understand, and can help to reduce the chances of errors or typos occurring.

The "Two branches in a conditional structure should not have exactly the same implementation" rule for SQL Server code states that when a conditional structure is used, such as an "IF/ELSE" statement, the two branches must have different implementations. This rule is important for ensuring that the code is optimized and that redundant code is avoided. The two branches should be distinct and have different implementations to ensure that the code is efficient and maintainable.

The rule "Unary prefix operators should not be repeated" states that unary prefix operators should not be used more than once in a statement. Unary prefix operators are operators that operate on one value, such as the minus sign (-) or the plus sign (+). Repeating these operators can lead to confusion and errors in the code, and should be avoided.

This rule states that any procedure or function parameters that are not used within the code should be removed. This helps to reduce unnecessary clutter and complexity in the code, while also making it easier to read and understand. Additionally, it can help to ensure that the code is performing optimally by eliminating any unused parameters that may be slowing down the execution time. Removing unused parameters can also help to reduce the risk of potential security vulnerabilities, as any potential attackers would have fewer parameters to exploit.

The rule "Variables should not be self-assigned" states that variables should not be assigned a value that is equal to its own existing value. This rule is important when writing SQL Server code, as assigning a variable to itself can lead to unexpected results. Self-assigning variables can also lead to poor performance, as the server will need to evaluate and assign the same value multiple times. In order to ensure optimal performance and accuracy, variables should only be assigned values that differ from their existing value.

This SQL Server code rule states that conditions in the WHERE clause of a query should not be contradictory. This means that the conditions should not be mutually exclusive or logically impossible. Contradictory conditions can lead to incorrect results and should be avoided.

For example, if a query contains the following WHERE clause:

WHERE age > 18 AND age < 18

This would be considered a contradictory condition as it is logically impossible for a person to be both older than 18 and younger than 18 at the same time. Therefore, this condition should be avoided.

The "WHERE clauses should not contain redundant conditions" code rule states that WHERE clauses should not contain conditions that are unnecessary or redundant. This means that the WHERE clause should only contain conditions that are necessary for the query to return the desired results. Redundant conditions can lead to inefficient query execution as the engine will need to process them unnecessarily. Furthermore, redundant conditions can lead to incorrect query results if the conditions are not logically equivalent. It is therefore important to ensure that the WHERE clause contains only the necessary conditions.