Order BY the IN value list

sql

advanced-sorting

postgresql

sql-functions

byAlex Kataev·Nov 10, 2024

To sort results by a custom list using the CASE statement in SQL, give this a shot:

SELECT * FROM table_name
WHERE column_name IN ('val1', 'val2', 'val3')
ORDER BY CASE column_name
           WHEN 'val1' THEN 1  -- Starting strong with numero uno!
           WHEN 'val2' THEN 2  -- Deuce making a close second
           WHEN 'val3' THEN 3  -- Last but not least, number three!
         END;

This approach fortifies your query output order in the sequence: 'val1', 'val2', 'val3'.

Advanced sorting techniques in PostgreSQL

Sorting using array_position (Postgres 9.6+)

Unleash the power of the array_position function:

SELECT * FROM table_name
WHERE column_name = ANY('{val1, val2, val3}'::text[])
ORDER BY array_position('{val1, val2, val3}'::text[], column_name);

array_position is your compass, it finds the index of each column_name value in the array, securing the order as appointed.

VALUES list with JOIN for precise ordering (PostgreSQL 8.3+)

Merge a VALUES list with a JOIN operation:

WITH val_list (column_name, order_seq) AS (
  VALUES ('val1', 1), ('val2', 2), ('val3', 3)
)
SELECT t.* 
FROM table_name t
JOIN val_list v ON t.column_name = v.column_name
ORDER BY v.order_seq;

The CTE makes your value list management a cakewalk while polishing the order.

Unpacking arrays with ordinality (Postgres 9.4+)

SELECT * FROM table_name t
JOIN unnest(ARRAY['val1', 'val2', 'val3']) WITH ORDINALITY AS u(column_name, order_seq) 
    ON t.column_name = u.column_name
ORDER BY u.order_seq;

unnest() with ORDINALITY is like the magic potion that assigns each value an unique number to abide by. No mess, no fuss!

Approaches for sorting suited to MySQL and other databases

Taking advantage of MySQL's FIELD function

Here's a MySQL exclusive method using the FIELD function:

SELECT * FROM table_name
WHERE column_name IN ('val1', 'val2', 'val3')
ORDER BY FIELD(column_name, 'val1', 'val2', 'val3');

The 'FIELD' solidifies the order according to the position in the list. It's like an artist guiding their brush strokes!

Keeping cross-database compatibility in mind

When juggling multiple SQL environments, knock out DB-specific quirks with standard SQL and conditional logic like the super-steady CASE.

Things to be cautious of and advanced problem-solving

The booby traps in manual sorting

While CASE might have your back, its manual operation makes it prone to oversight. Using array functions can make sure you're always on the tightrope.