What is row number, rank, dense rank? explain partition by, indexing joins, query optimization techniques

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Explanation of row number, rank, dense rank, partition by, indexing joins, and query optimization techniques.

Row number is a function that assigns a unique number to each row in a result set.
Rank is a function that assigns a rank to each row based on the values in a specified column.
Dense rank is a function that assigns a rank to each row based on the values in a specified column, but with no gaps in the ranking.
Partition by is a clause that divides a result set into partitions based on a specified column or columns.
Indexing joins involve using indexes to speed up join operations between tables.
Query optimization techniques involve optimizing SQL queries to improve performance, such as using indexes, minimizing subqueries, and avoiding unnecessary joins.

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