BE AWARE FOLLOWING THING WHILE WRITING SQL QUERY

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Queries

Writing efficient queries in SQL Server is more an exercise in writing elegant relational queries than in knowing specific tricks and syntax tips. Generally, a well-written, relationally correct query written against a well-designed relationally correct database model that uses the correct indexes produces a system that performs fairly well and that is scalable. The following guidelines may help you create efficient queries:

• Know the performance and scalability characteristics of queries.
• Write correctly formed queries.
• Return only the rows and columns needed.
• Avoid expensive operators such as NOT LIKE.
• Avoid explicit or implicit functions in WHERE clauses.
• Use locking and isolation level hints to minimize locking.
• Use stored procedures or parameterized queries.
• Minimize cursor use.
• Avoid long actions in triggers.
• Use temporary tables and table variables appropriately.
• Limit query and index hints use.
• Fully qualify database objects

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