Find possible duplicates in two columns ignoring case and special characters

Question

Query

SELECT COUNT(*), name, number
FROM   tbl
GROUP  BY name, number
HAVING COUNT(*) > 1

It sometimes fails to find duplicates between lowe

Answer 1

PostgreSQL by default is case sensitive. You can force it to be case-insensitive during searches by converting all values to a single case:

SELECT COUNT(*), lower(name), number FROM TABLE 
GROUP BY lower(name), number HAVING COUNT(*) > 1

• NOTE: This has not been tested in Postgres