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SQL - Queries Tuning and Optimization Techniques

In SQL, it is very difficult to write complex SQL queries involving joins across many (at least 3-4) tables and involving several nested conditions because a SQL statement, once it reaches a certain level of complexity, is basically a little program in and of itself.  A database index is a data structure that improves the speed of operations on a database table. Indexes can be created using one or more columns of a database table, providing the basis for both rapid random look ups and efficient access of ordered records. Indexing is incredibly important when working with large tables, however, occasionally smaller tables should be indexed, if they are expected to grow.


Try to consistently indent and don't be afraid to use multiple lines. You don't have to write it all at once. Complex queries can sometimes just be a collection of simple queries. You need to follow some basic guidelines and Take the time to think these through such as-
List all of the columns that are to be return…