Best practices for table in SQL Server
- Every table should have Primary Key Constraint on column with Unique Values.
- Every table should have a Clustered Index preferably (not mandatory) on Primary Key column.
- Explicitly define the Foreign Key constraint on Foreign key column.
- Every Foreign Key should have a Non Clustered Index.
- You can create Composite Index but try to avoid too many columns in a Composite Index.
- Define the Unique constraint on unique column or set of columns.
- Create the Covering Index on mostly referred columns to avoid look ups.
- Create Filtered Index on column with known value which is going to be used most frequently.
- Define the Default Constraint wherever applicable.
- Define the Check Constraint on columns with fixed set of values.
- Define the extended properties for the columns to add description about the table, column, value it will hold etc. so that other people can understand the schema easily.
- Avoid creating Clustered Index on CHAR, VARCHAR or NVARCHAR columns.
- Do not create Index on column with LOB Data Type.
- In case of Composite Index, the first column of Index should be with good Cardinality & Selectivity.
Cardinality refers to the uniqueness of data values contained in a column. High cardinality means that the column contains less number of duplicate values. Low cardinality means that the column contains a lot of duplicate values.
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Please don’t use any of the examples discussed in this article in Production without evaluating it based on your need.