Sql order string as number

sql

string-sorting

performance

cte

byNikita Barsukov·Aug 10, 2024

Bring order to the chaos of string numbers with the CAST function:

SELECT * FROM your_table ORDER BY CAST(string_number AS INT);

In a numeric utopia like MySQL, non-numeric characters are anarchists. Exile them with regexp_replace before casting:

-- MySQL example
SELECT * FROM your_table ORDER BY CAST(regexp_replace(string_number, '\\D', '') AS UNSIGNED);

This provides a sane order to your string_number column by stripping away non-digits.

String number sorting

Numbers masquerading as strings like '1', '10', '2' aren't fooled by lexicographical sorting - they need explicit casting or mathematical operations to fall into their proper numeric order.

The magic of length and value

For armies of numbers stringified to varying lengths, marshal them by length first, then by actual value:

SELECT * FROM your_table ORDER BY LENGTH(string_number), CAST(string_number AS UNSIGNED);

This gives smaller numbers precedence, sorting '2' before '10.'

Battle of mixed types

In a world where numeric and alphanumeric characters coexist, wield a CASE statement for justice:

SELECT * FROM your_table
ORDER BY 
  CASE 
    WHEN string_number REGEXP '^[0-9]+$' THEN 1 
    ELSE 2 
  END, 
  LENGTH(string_number),
  string_number;

Now, numeric strings lead the parade, followed by their alphanumeric peers.

Beware of performance consciousness

Working with large armies of data may lead to rectification after using functions like CAST or LENGTH within ORDER BY. Indexing expressions or working on smaller cohorts of data can avert a performance mayday.

Sorting positive and negative strings to numbers

Positive and negative number strings aren't left to their own disorderly devices. ABS function ushers them into their rightful numeric places:

SELECT * FROM your_table ORDER BY ABS(string_number);

The above line of code enforces a dictatorship of absolute values.

Additional tactical sorting maneuvers

CTEs (Common Table Expressions) and temporary tables are powerful allies for complex sorting operations. Wrap the sorting logic in a cozy CTE blanket to simplify your main query.

CTE to the rescue

WITH OrderedValues AS (
  SELECT string_number,
    CASE 
      WHEN string_number REGEXP '^[0-9]+$' THEN CAST(string_number AS INT) 
      WHEN string_number REGEXP '^[0-9]+\\.' THEN CAST(SUBSTRING_INDEX(string_number, '.', 1) AS INT) 
      ELSE 0 
    END AS OrderValue
  FROM your_table
)
SELECT * FROM OrderedValues ORDER BY OrderValue, string_number;

This CTE plays nanny to your strings, preparing them for a gentle sorting.

Guiding principles

Regardless of the SQL path taken, mind these guiding principles:

Zero-prefixed values: Use LTRIM to deal with stingy zeroes hanging onto your numbers.
Alphanumeric sorting: Rely on MySQL's expertise in converting string starters to numbers.
Validation: Poke and prod your results to see if they hold true across diverse datasets.
System impact: When an ecosystem depends on your sort operation, make calculated moves. There may be roadblocks affecting performance and data integrity.