order of execution sql code example

Example 1: sql order of execution query

SQL order of execution defines the
execution order of clauses.

-Select
It starts execution with 
-from  (Choose and join tables to get base data)
after from
-where ( filters base data )
-group by (Aggregates base data)
-having (filters aggregated data)
-select (returns final data)
-order by (sorts the final data)
-limit (limits the returned data to a row count)

Only select and from are mandatory

Example 2: sql order of operations

SELECT DISTINCT column, AGG_FUNC(column_or_expression), …
FROM mytable
    JOIN another_table
      ON mytable.column = another_table.column
    WHERE constraint_expression
    GROUP BY column
    HAVING constraint_expression
    ORDER BY column ASC/DESC
    LIMIT count OFFSET COUNT;

Example 3: SQL Order of execution

1. FROM (including joins)
2. WHERE
3. GROUP BY
4. HAVING
5. SELECT
6. ORDER BY

Example 4: SQL Order of execution

1. FROM
2. WHERE
3. GROUP BY
4. HAVING
5. SELECT
6. ORDER BY




    The rows selected by a query are filtered first by the FROM clause join conditions, then the WHERE clause search conditions, and then the HAVING clause search conditions. Inner joins can be specified in either the FROM or WHERE clause without affecting the final result.

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