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Nested queries

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• Nested Queries
  • Nested query:

    A nested query is a SELECT query where the WHERE clause contains subquery.

  • Schematically:

    SELECT ... FROM ... WHERE ... (SELECT ... /* Subquery */ FROM ... WHERE ...)

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  • In theory, nesting can be arbitrarily deep :

    SELECT ... FROM ... WHERE ... (SELECT ... FROM ... WHERE ... (SELECT ... FROM ... WHERE ...)

  • In practice, depending on your DBMS system, the number of nesting levels is limited (and different for each system)

    According to click here, MySQL can have 61 levels of nested selects.