Index Scan retrieves all the rows from the table. Index Seek retrieves selective rows from the table.
SQL SERVER – Difference between DISTINCT and GROUP BY – Distinct vs Group By
What is the difference between DISTINCT and GROUP BY? They usually produce the same plan. Use GROUP BY for aggregates and DISTINCT to remove duplicates.
SQL SERVER – SQL Commandments – Suggestions, Tips, Tricks
My 20 SQL Commandments for SQL Server, rewritten from an Oracle article: know your data, test with realistic data, write identical statements, and more tips.
SQL SERVER – FIX : Error 15023: User already exists in current database.
Error 15023: User already exists in current database. I fix it with sp_change_users_login, using Report, Auto_Fix or Update_One to link the user to a login.
SQL SERVER – Primary Key Constraints and Unique Key Constraints
Primary Key and Unique Key both enforce uniqueness, but they differ in the index they create and in NULL handling. Here are the differences and the scripts.
SQL SERVER – ReIndexing Database Tables and Statistics with Targeted Maintenance
ReIndexing Database tables starts with a measured maintenance need. I check the workload before choosing an index operation.