SQL Why Table Indexes.

Where, What and Why Index?

  • In a relational database management system, an index is a mechanism for boosting performance.
  • This is true for the selecting of data from tables, but not for the updates, it may be slow down the performance.
  • Create a unique index on the column or columns included in the PRIMARY KEY of a table as the PRIMARY KEY is often used in connection with other tables.
  • A column that appears often in sorted order should be indexed so that the system can take advantage of an indexed sort.
  • Columns that are regularly used in joins should be indexed because the database management system performs the join faster.
  • Columns, which is used to search for upper or lower limits can be a good choice for indexing.
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