SQL order of query execution

The order in which the various SQL statements appear in a query is as follows:

  1. SELECT
  2. FROM
  3. [JOIN]
  4. WHERE
  5. GROUP BY
  6. HAVING
  7. WINDOW
  8. ORDER BY

ome of the important points that you should keep in mind while writing a query are as follows:

  • Use inner joins wherever possible to avoid having any unnecessary rows in the resultant table.
  • Apply all the required filters to get only the required data values from multiple tables.
  • Index the columns that are frequently used in the WHERE clause.
  • Avoid using DISTINCT while using the GROUP BY clause, as it slows down query processing.
  • Avoid using SELECT * as much as possible. Select only the required columns.
  • Use the ORDER BY clause only if it is absolutely necessary, as it is processed late in a query.
  • Avoid using LIMIT and OFFSET as much as possible. Instead, apply appropriate filters using the WHERE clause.