MySQL. List all indices in the schema

indices.sql

SELECT
    CONCAT(
        'ALTER TABLE ',
        TABLE_NAME,
        ' ADD ',
        CASE
            WHEN MAX(NON_UNIQUE) = 1 THEN 'INDEX '
            ELSE 'UNIQUE INDEX '
        END,
        INDEX_NAME,
        ' (',
        GROUP_CONCAT(
            COLUMN_NAME
            ORDER BY
                SEQ_IN_INDEX
        ),
        ');'
    ) AS alter_statement
FROM
    information_schema.STATISTICS
WHERE
    TABLE_SCHEMA = DATABASE()
GROUP BY
    TABLE_NAME,
    INDEX_NAME;