T-SQL

Overview

We use the Repository pattern with the MSSQL repositories being written using Dapper. Each repository method in turn calls a Stored Procedure, which primarily fetches data from Views.

Best practices

Consistency: Follow established patterns throughout the codebase
Readability: Prioritize code readability and maintainability
Performance: Consider index usage and query optimization
Security: Use parameterized queries and proper data type validation
Modularity: Break complex operations into smaller, reusable procedures

File organization

Directory structure

Schema-based organization: Files are organized by domain/schema (Auth, Billing, Secrets Manager, Vault, etc.)
Object type grouping: Within each domain, files are grouped by type:
- Tables/ - Table definitions
- Views/ - View definitions
- Stored Procedures/ - Stored procedure definitions
- Functions/ - User-defined functions
Root-level objects: Common objects are placed directly in dbo/:
- Stored Procedures/ - General stored procedures
- Tables/ - Core tables
- Views/ - General views
- User Defined Types/ - Custom data types

File naming conventions

Stored Procedures: {EntityName}_{Action}.sql
- e.g. User_Create.sql, Organization_ReadById.sql
Tables: {EntityName}.sql
- e.g. User.sql, Organization.sql
Views: {EntityName}View.sql or {EntityName}{Purpose}View.sql
- e.g. UserView.sql, ApiKeyDetailsView.sql
Functions: {EntityName}{Purpose}.sql
- e.g. UserCollectionDetails.sql
User Defined Types: {TypeName}.sql
- e.g. GuidIdArray.sql

Versioning

When a new version of an entity is introduced and needs to be maintained next to the existing one during deployment, use versioned names for the different scripts, so that the relationship is clear - e.g. a _V2 suffix.

Code style

General standards

These standards should be applied across any T-SQL scripts that you write.

Indentation: Use 4 spaces (not tabs) for all SQL code files
Keywords: Use UPPERCASE for all SQL keywords (CREATE, SELECT, FROM, WHERE, GROUP BY, ORDER BY, JOIN, ON, INTO, TOP, etc.)
Object names: Always use square brackets [dbo].[TableName]
Schema: Use [dbo] prefix for all objects
Line endings: Use consistent line breaks with proper indentation
Vertical lists: Vertically list items as much as feasibly possible, and use consistent indentation to make vertical listing quick and easy. A vertical list is much easier to compare and makes code changes easily detectable
Blank lines: Separate sections of code with at least one blank line
Commas: Commas should be placed at the right end of the line
Parentheses: Parentheses should be vertically aligned with spanning multiple lines

`SELECT` statements

SELECT keyword on its own line
Column names indented (4 spaces)
One column per line for multi-column selects
Call out the specific table/alias for where a column is from when joining to other tables
FROM keyword on separate line, aligned with SELECT
FROM clause indented (4 spaces)
- Use aliases for table names when joining to other tables
JOIN keywords on separate line, aligned with FROM
- Use full join specifications (INNER JOIN vs JOIN, LEFT OUTER JOIN vs LEFT JOIN, etc)
JOIN clauses indented to align with table/column name(s)
WHERE keyword on separate line, aligned with FROM/JOIN
WHERE clause on separate lines, indented to align with table/column name(s)

SELECT
    U.[Id],
    U.[Name],
    U.[Email],
    OU.[OrganizationId]
FROM
    [dbo].[User] U
INNER JOIN
    [dbo].[OrganizationUser] OU ON U.[Id] = OU.[UserId]
WHERE
    U.[Enabled] = 1

Stored procedures

Stored Procedure Name: {EntityName}_{Action} format (e.g., [dbo].[User_ReadById])
- EntityName: The main table or concept (e.g. User, Organization, Cipher)
- Action: What the procedure does (e.g. Create, ReadById, DeleteMany)
Parameters: Start with @ and use PascalCase (e.g., @UserId, @OrganizationId)
OUTPUT parameters: Explicitly declare with OUTPUT keyword

Example of common CRUD operations

Create: {EntityName}_Create procedures
Read: {EntityName}_ReadById, {EntityName}_ReadBy{Criteria} procedures
Read Many: {EntityName}_ReadManyByIds, {EntityName}_ReadManyBy{Criteria} procedures
Update: {EntityName}_Update procedures
Delete: {EntityName}_DeleteById, {EntityName}_Delete procedures

Basic structure

CREATE PROCEDURE [dbo].[EntityName_Action]
    @Parameter1 DATATYPE,
    @Parameter2 DATATYPE = NULL,
    @Parameter3 DATATYPE OUTPUT
AS
BEGIN
    SET NOCOUNT ON

    -- Procedure logic here

END

Parameter declaration

One parameter per line
Align parameters with consistent indentation (4 spaces)
Default values on same line as parameter
OUTPUT parameters clearly marked

Default parameter values

When adding parameters to an existing stored procedure, a default value must be specified to ensure backward compatibility and ensure existing code can be called without modification.

Use SET NOCOUNT ON to prevent the automatic return of row count messages, which improves performance and ensures consistent behavior across different client applications that might handle these messages differently.

`INSERT` statements

Column list in parentheses, one column per line
VALUES clause with parameters aligned
Proper indentation for readability

INSERT INTO [dbo].[TableName]
(   [Column1],
    [Column2],
    [Column3]
)
VALUES
(   @Parameter1,
    @Parameter2,
    @Parameter3
)

`UPDATE` statements

UPDATE and table name on different lines
SET clause with each column assignment on separate line
WHERE clause clearly separated

UPDATE
    [dbo].[TableName]
SET
    [Column1] = @Parameter1,
    [Column2] = @Parameter2,
    [Column3] = @Parameter3
WHERE
    [Id] = @Id

Tables

Table Name: PascalCase (e.g., [dbo].[User], [dbo].[AuthRequest])
Column Names: PascalCase (e.g., [Id], [CreationDate], [MasterPasswordHash])
Primary Key: PK_{TableName} (e.g., [PK_User], [PK_Organization])
Foreign Keys: FK_{TableName}_{ReferencedTable} (e.g., FK_Device_User)
Default Constraints: DF_{TableName}_{ColumnName} (e.g., [DF_Organization_UseScim])

Column definitions

Alignment: Column names, data types, and nullability vertically aligned using spaces
Data Types: Use consistent type patterns:
- UNIQUEIDENTIFIER for IDs
- DATETIME2(7) for timestamps
- NVARCHAR(n) for Unicode text
- VARCHAR(n) for ASCII text
- BIT for boolean values
- TINYINT, SMALLINT, INT, BIGINT for integers
Nullability: Explicitly specify NOT NULL or NULL
Standard Columns: Most tables include:
- [Id] UNIQUEIDENTIFIER NOT NULL - Primary key
- [CreationDate] DATETIME2(7) NOT NULL - Record creation timestamp
- [RevisionDate] DATETIME2(7) NOT NULL - Last modification timestamp

CREATE TABLE [dbo].[TableName]
(
    [Column1] INT IDENTITY(1,1) NOT NULL,
    [Column2] NVARCHAR(100) NOT NULL,
    [Column3] NVARCHAR(255) NULL,
    [Column4] BIT NOT NULL CONSTRAINT [DF_TableName_Column4] DEFAULT (1),

    CONSTRAINT [PK_TableName] PRIMARY KEY CLUSTERED ([Column1] ASC)
);

Views

View Name:
- {EntityName}View
  - Used when the view maps closely to a single table, with little or no joins. (e.g., [dbo].[ApiKeyView] from ApiKey)
- {EntityName}DetailsView for complex views
  - Used for views that combine multiple tables or add logic beyond a basic table select. These usually serve a specific display or reporting use case and are named to reflect the context (e.g., [dbo].[OrganizationUserDetailsView])
- For views that combine entities, create a view with a clear name tied to the main entity (e.g., [dbo].[OrganizationUser_MemberAccessDetailsView]) and a stored procedure that reads from it (e.g., [dbo].[MemberAccessDetails_ReadByUserId]).

Simple views

CREATE VIEW [dbo].[ViewName]
AS
SELECT
    *
FROM
    [dbo].[TableName]

Complex views

CREATE VIEW [dbo].[ComplexViewName]
AS
SELECT
    T1.[Column1],
    T1.[Column2],
    T2.[Column3],
    CASE
        WHEN T2.[Column4] IS NOT NULL
        THEN 1
        ELSE 0
    END AS ColumnAlias
FROM
    [dbo].[Table1] T1
LEFT JOIN
    [dbo].[Table2] T2 ON T1.[Id] = T2.[ForeignId]
WHERE
    T1.[Enabled] = 1

Functions

Function Name: [Schema].[FunctionName] (e.g., [dbo].[UserCollectionDetails])
- The name should describe what the function returns

CREATE FUNCTION [dbo].[FunctionName](@Parameter DATATYPE)
RETURNS TABLE
AS RETURN
SELECT
    Column1,
    Column2,
    CASE
        WHEN Condition
        THEN Value1
        ELSE Value2
    END [ComputedColumn]
FROM
    [dbo].[TableName]
WHERE
    [FilterColumn] = @Parameter

User defined types

User Defined Type Name: [Schema].[TypeName] (e.g., [dbo].[GuidIdArray])
- The name should describe the type

CREATE TYPE [dbo].[TypeName] AS TABLE
(   [Column1] DATATYPE NOT NULL,
    [Column2] DATATYPE NOT NULL
);

Indexes

Index Name: IX_{TableName}_{ColumnName(s)} (e.g., [IX_User_Email])
- The name should clearly indicate the table and the columns being indexed

CREATE NONCLUSTERED INDEX [IX_OrganizationUser_UserIdOrganizationIdStatus]
   ON [dbo].[OrganizationUser]([UserId] ASC, [OrganizationId] ASC, [Status] ASC)
   INCLUDE ([AccessAll])

Error handling

Use SET NOCOUNT ON in stored procedures
Implement appropriate transaction handling where needed
Follow consistent error reporting patterns
- Business logic should not be in stored procedures, but there may be times when it makes sense to do error handling in other scripts (migrations, one-off data scrubs)

BEGIN TRY
    BEGIN TRANSACTION;

    UPDATE
        [dbo].[TableName]
    SET
        [Column1] = 'NewValue'
    WHERE
        [Id] = 'IdValue'


    UPDATE
        [dbo].[TableName2]
    SET
        [Column1] = 'NewValue'
    WHERE
        [Id] = 'IdValue'

    COMMIT TRANSACTION;

END TRY
BEGIN CATCH

    IF @@TRANCOUNT > 0
        ROLLBACK TRANSACTION;

    THROW;

END CATCH;

Comments and documentation

Use -- for single-line comments
Add comments for complex business logic and the reason for a command or block of code
Document magic numbers and status codes (e.g., -- 2 = Confirmed)
Provide brief explanations for complex CASE statements or calculations
Don't comment unnecessarily, such as commenting that an insert statement is about to be executed

Deployment scripts

There are specific ways migration scripts should be structured. We do so to adhere to the following guiding principles:

It must be idempotent: Always ensure a migration can be run multiple times without causing errors or duplicating data.
It must avoid breaking changes: Migrations should never delete or rename columns that are still in use by deployed code.
It must maintain schema integrity: The schema of the database defined in code should map exactly to the schema of the database in all deployed environments.
It must be backwards compatible: Code should be able to work with both the old and new schema during a rolling deployment.

Tables

Creating a table

When creating a table, you must first check if the table exists:

IF OBJECT_ID('[dbo].[{table_name}]') IS NULL
BEGIN
    CREATE TABLE [dbo].[{table_name}]
    (   [Id]                UNIQUEIDENTIFIER NOT NULL,
        [Column1]           DATATYPE         NOT NULL,
        [Column2]           DATATYPE         NULL,
        [CreationDate]      DATETIME2(7)     NOT NULL,
        [RevisionDate]      DATETIME2(7)     NOT NULL,
        CONSTRAINT [PK_{table_name}] PRIMARY KEY CLUSTERED ([Id] ASC),
        CONSTRAINT [FK_{table_name}_{referenced_table}] FOREIGN KEY ([ForeignKeyColumn]) REFERENCES [dbo].[ReferencedTable] ([Id])
    );
END
GO

Deleting a table

When deleting a table, use IF EXISTS to avoid an error if the table doesn't exist.

DROP IF EXISTS [dbo].[{table_name}]
GO

Adding a column to a table

You must first check to see if the column exists before adding it to the table.

IF COL_LENGTH('[dbo].[{table_name}]', '{column_name}') IS NULL
BEGIN
    ALTER TABLE [dbo].[{table_name}]
        ADD [{column_name}] {DATATYPE} {NULL|NOT NULL};
END
GO

When adding a new NOT NULL column to an existing table, please re-evaluate the need for it to truly be required. Do not be afraid of using Nullable<T> primitives in C# and in the application layer, which is almost always going to be better than taking up unnecessary space in the DB per row with a default value, especially for new functionality or features where it will take a very long time to be useful for most row-level data, if at all.

If you do decide to add a NOT NULL column, use a DEFAULT constraint instead of creating the column, updating rows and changing the column. This is especially important for the largest tables like dbo.User and dbo.Cipher. Our version of SQL Server in Azure uses metadata for default constraints. This means we can update the default column value without updating every row in the table (which will use a lot of DB I/O).

This is slow:

IF COL_LENGTH('[dbo].[Table]', 'Column') IS NULL
BEGIN
    ALTER TABLE
        [dbo].[Table]
    ADD
        [Column] INT NULL
END
GO

UPDATE
    [dbo].[Table]
SET
    [Column] = 0
WHERE
    [Column] IS NULL
GO

ALTER TABLE
    [dbo].[Column]
ALTER COLUMN
    [Column] INT NOT NULL
GO

This is better:

IF COL_LENGTH('[dbo].[Table]', 'Column' IS NULL
BEGIN
    ALTER TABLE
        [dbo].[Column]
    ADD
        [Column] INT NOT NULL CONSTRAINT DF_Table_Column DEFAULT 0
END
GO

Changing a column data type

You must wrap the ALTER TABLE statement in a conditional block, so that subsequent runs of the script will not modify the data type again.

IF EXISTS (
    SELECT *
    FROM INFORMATION_SCHEMA.COLUMNS
    WHERE COLUMN_NAME = '{column_name}' AND
        DATA_TYPE = '{datatype}' AND
        TABLE_NAME = '{table_name}')
BEGIN
    ALTER TABLE [dbo].[{table_name}]
    ALTER COLUMN [{column_name}] {NEW_TYPE} {NULL|NOT NULL}
END
GO

Adjusting metadata

When adjusting a table, you should also check to see if that table is referenced in any views. If the underlying table in a view has been modified, you should run sp_refreshview to re-generate the view metadata.

EXECUTE sp_refreshview N'[dbo].[{view_name}]'
GO

Views

Creating or modifying a view

We recommend using the CREATE OR ALTER syntax for adding or modifying a view.

CREATE OR ALTER VIEW [dbo].[{view_name}]
AS
SELECT
    *
FROM
    [dbo].[{table_name}]
GO

Deleting a view

When deleting a view, use IF EXISTS to avoid an error if the table doesn't exist.

DROP IF EXISTS [dbo].[{view_name}]
GO

Adjusting metadata

When altering views, you may also need to refresh modules (stored procedures or functions) that reference that view or function so that SQL Server to update its statistics and compiled references to it.

IF OBJECT_ID('[dbo].[{procedure_or_function}]') IS NOT NULL
BEGIN
    EXECUTE sp_refreshsqlmodule N'[dbo].[{procedure_or_function}]';
END
GO

Functions and stored procedures

Creating or modifying a function or stored procedure

We recommend using the CREATE OR ALTER syntax for adding or modifying a function or stored procedure.

CREATE OR ALTER {PROCEDURE|FUNCTION} [dbo].[{sproc_or_func_name}]
...
GO

Deleting a function or stored procedure

When deleting a function or stored procedure, use IF EXISTS to avoid an error if it doesn't exist.

DROP IF EXISTS [dbo].[{sproc_or_func_name}]
GO

Indexes

When creating indexes, especially on heavily used tables, our production database can easily become offline, unusable, hit 100% CPU and many other bad behaviors. Our production database is configured to do online index builds by default, (so as not to lock the underlying table), so you should not specify ONLINE = ON, as this may cause failures on some SQL Server editions that do not support online index rebuilds. Online index creation may cause the index operation to take longer, but it will not create an underlying schema table lock which prevents all reads and connections to the table and instead only locks the table of updates during the operation.

A good example is when creating an index on dbo.Cipher or dbo.OrganizationUser, those are heavy-read tables and the locks can cause exceptionally high CPU, wait times and worker exhaustion in Azure SQL.

CREATE NONCLUSTERED INDEX [IX_OrganizationUser_UserIdOrganizationIdStatus]
   ON [dbo].[OrganizationUser]([UserId] ASC, [OrganizationId] ASC, [Status] ASC)
   INCLUDE ([AccessAll])

Index best practices

Create indexes after table definition with GO separator
Include INCLUDE clause when beneficial for covering indexes
Use filtered indexes with WHERE clause when appropriate

Overview​

Best practices​

File organization​

Directory structure​

File naming conventions​

Code style​

General standards​

SELECT statements​

Stored procedures​

Basic structure​

Parameter declaration​

INSERT statements​

UPDATE statements​

Tables​

Column definitions​

Views​

Simple views​

Complex views​

Functions​

User defined types​

Indexes​

Error handling​

Comments and documentation​

Deployment scripts​

Tables​

Creating a table​

Deleting a table​

Adding a column to a table​

Changing a column data type​

Adjusting metadata​

Views​

Creating or modifying a view​

Deleting a view​

Adjusting metadata​

Functions and stored procedures​

Creating or modifying a function or stored procedure​

Deleting a function or stored procedure​

Indexes​

Index best practices​

Overview

Best practices

File organization

Directory structure

File naming conventions

Code style

General standards

`SELECT` statements

Stored procedures

Basic structure

Parameter declaration

`INSERT` statements

`UPDATE` statements

Tables

Column definitions

Views

Simple views

Complex views

Functions

User defined types

Indexes

Error handling

Comments and documentation

Deployment scripts

Tables

Creating a table

Deleting a table

Adding a column to a table

Changing a column data type

Adjusting metadata

Views

Creating or modifying a view

Deleting a view

Adjusting metadata

Functions and stored procedures

Creating or modifying a function or stored procedure

Deleting a function or stored procedure

Indexes

Index best practices