# sqlglot.optimizer.normalize_identifiers API documentation

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# sqlglot.optimizer.normalize_identifiers

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     1from __future__ import annotations
     2
     3import typing as t
     4
     5from sqlglot import exp
     6from sqlglot.dialects.dialect import Dialect, DialectType
     7
     8if t.TYPE_CHECKING:
     9    from sqlglot._typing import E
    10
    11
    12@t.overload
    13def normalize_identifiers(expression: E, dialect: DialectType = None) -> E: ...
    14
    15
    16@t.overload
    17def normalize_identifiers(expression: str, dialect: DialectType = None) -> exp.Identifier: ...
    18
    19
    20def normalize_identifiers(expression, dialect=None):
    21    """
    22    Normalize identifiers by converting them to either lower or upper case,
    23    ensuring the semantics are preserved in each case (e.g. by respecting
    24    case-sensitivity).
    25
    26    This transformation reflects how identifiers would be resolved by the engine corresponding
    27    to each SQL dialect, and plays a very important role in the standardization of the AST.
    28
    29    It's possible to make this a no-op by adding a special comment next to the
    30    identifier of interest:
    31
    32        SELECT a /* sqlglot.meta case_sensitive */ FROM table
    33
    34    In this example, the identifier `a` will not be normalized.
    35
    36    Note:
    37        Some dialects (e.g. DuckDB) treat all identifiers as case-insensitive even
    38        when they're quoted, so in these cases all identifiers are normalized.
    39
    40    Example:
    41        >>> import sqlglot
    42        >>> expression = sqlglot.parse_one('SELECT Bar.A AS A FROM "Foo".Bar')
    43        >>> normalize_identifiers(expression).sql()
    44        'SELECT bar.a AS a FROM "Foo".bar'
    45        >>> normalize_identifiers("foo", dialect="snowflake").sql(dialect="snowflake")
    46        'FOO'
    47
    48    Args:
    49        expression: The expression to transform.
    50        dialect: The dialect to use in order to decide how to normalize identifiers.
    51
    52    Returns:
    53        The transformed expression.
    54    """
    55    dialect = Dialect.get_or_raise(dialect)
    56
    57    if isinstance(expression, str):
    58        expression = exp.parse_identifier(expression, dialect=dialect)
    59
    60    for node in expression.walk(prune=lambda n: n.meta.get("case_sensitive")):
    61        if not node.meta.get("case_sensitive"):
    62            dialect.normalize_identifier(node)
    63
    64    return expression

def normalize_identifiers(expression, dialect=None): View Source

    21def normalize_identifiers(expression, dialect=None):
    22    """
    23    Normalize identifiers by converting them to either lower or upper case,
    24    ensuring the semantics are preserved in each case (e.g. by respecting
    25    case-sensitivity).
    26
    27    This transformation reflects how identifiers would be resolved by the engine corresponding
    28    to each SQL dialect, and plays a very important role in the standardization of the AST.
    29
    30    It's possible to make this a no-op by adding a special comment next to the
    31    identifier of interest:
    32
    33        SELECT a /* sqlglot.meta case_sensitive */ FROM table
    34
    35    In this example, the identifier `a` will not be normalized.
    36
    37    Note:
    38        Some dialects (e.g. DuckDB) treat all identifiers as case-insensitive even
    39        when they're quoted, so in these cases all identifiers are normalized.
    40
    41    Example:
    42        >>> import sqlglot
    43        >>> expression = sqlglot.parse_one('SELECT Bar.A AS A FROM "Foo".Bar')
    44        >>> normalize_identifiers(expression).sql()
    45        'SELECT bar.a AS a FROM "Foo".bar'
    46        >>> normalize_identifiers("foo", dialect="snowflake").sql(dialect="snowflake")
    47        'FOO'
    48
    49    Args:
    50        expression: The expression to transform.
    51        dialect: The dialect to use in order to decide how to normalize identifiers.
    52
    53    Returns:
    54        The transformed expression.
    55    """
    56    dialect = Dialect.get_or_raise(dialect)
    57
    58    if isinstance(expression, str):
    59        expression = exp.parse_identifier(expression, dialect=dialect)
    60
    61    for node in expression.walk(prune=lambda n: n.meta.get("case_sensitive")):
    62        if not node.meta.get("case_sensitive"):
    63            dialect.normalize_identifier(node)
    64
    65    return expression

Normalize identifiers by converting them to either lower or upper case, ensuring the semantics are preserved in each case (e.g. by respecting case-sensitivity).

This transformation reflects how identifiers would be resolved by the engine corresponding to each SQL dialect, and plays a very important role in the standardization of the AST.

It's possible to make this a no-op by adding a special comment next to the identifier of interest:

    SELECT a /* sqlglot.meta case_sensitive */ FROM table

In this example, the identifier `a` will not be normalized.

###### Note:

> Some dialects (e.g. DuckDB) treat all identifiers as case-insensitive even when they're quoted, so in these cases all identifiers are normalized.

###### Example:

>     >>> import sqlglot
>     >>> expression = sqlglot.parse_one('SELECT Bar.A AS A FROM "Foo".Bar')
>     >>> normalize_identifiers(expression).sql()
>     'SELECT bar.a AS a FROM "Foo".bar'
>     >>> normalize_identifiers("foo", dialect="snowflake").sql(dialect="snowflake")
>     'FOO'

###### Arguments:

- expression: The expression to transform.
- dialect: The dialect to use in order to decide how to normalize identifiers.

###### Returns:

> The transformed expression.