sql execution order 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 alter table order by

ALTER TABLE tablename ORDER BY columnname ASC;.