"""
SQL utilities.
"""

from typing import Collection


def placeholders(params: Collection) -> str:
    """For SQL query construction: return a string of n SQL placeholders for a
    collection of n params.

    Args:
        params: Collection of params.

    Example:
        >>> placeholders([1, 2, 3])
        '%s,%s,%s'
    """
    return ",".join(["%s"] * len(params))