1# ruff: noqa: F401
 2"""
 3## Dialects
 4
 5While there is a SQL standard, most SQL engines support a variation of that standard. This makes it difficult
 6to write portable SQL code. SQLGlot bridges all the different variations, called "dialects", with an extensible
 7SQL transpilation framework.
 8
 9The base `sqlglot.dialects.dialect.Dialect` class implements a generic dialect that aims to be as universal as possible.
10
11Each SQL variation has its own `Dialect` subclass, extending the corresponding `Tokenizer`, `Parser` and `Generator`
12classes as needed.
13
14### Implementing a custom Dialect
15
16Creating a new SQL dialect may seem complicated at first, but it is actually quite simple in SQLGlot:
17
18```python
19from sqlglot import exp
20from sqlglot.dialects.dialect import Dialect
21from sqlglot.generator import Generator
22from sqlglot.tokens import Tokenizer, TokenType
23
24
25class Custom(Dialect):
26    class Tokenizer(Tokenizer):
27        QUOTES = ["'", '"']  # Strings can be delimited by either single or double quotes
28        IDENTIFIERS = ["`"]  # Identifiers can be delimited by backticks
29
30        # Associates certain meaningful words with tokens that capture their intent
31        KEYWORDS = {
32            **Tokenizer.KEYWORDS,
33            "INT64": TokenType.BIGINT,
34            "FLOAT64": TokenType.DOUBLE,
35        }
36
37    class Generator(Generator):
38        # Specifies how AST nodes, i.e. subclasses of exp.Expression, should be converted into SQL
39        TRANSFORMS = {
40            exp.Array: lambda self, e: f"[{self.expressions(e)}]",
41        }
42
43        # Specifies how AST nodes representing data types should be converted into SQL
44        TYPE_MAPPING = {
45            exp.DataType.Type.TINYINT: "INT64",
46            exp.DataType.Type.SMALLINT: "INT64",
47            exp.DataType.Type.INT: "INT64",
48            exp.DataType.Type.BIGINT: "INT64",
49            exp.DataType.Type.DECIMAL: "NUMERIC",
50            exp.DataType.Type.FLOAT: "FLOAT64",
51            exp.DataType.Type.DOUBLE: "FLOAT64",
52            exp.DataType.Type.BOOLEAN: "BOOL",
53            exp.DataType.Type.TEXT: "STRING",
54        }
55```
56
57The above example demonstrates how certain parts of the base `Dialect` class can be overridden to match a different
58specification. Even though it is a fairly realistic starting point, we strongly encourage the reader to study existing
59dialect implementations in order to understand how their various components can be modified, depending on the use-case.
60
61----
62"""
63
64from sqlglot.dialects.athena import Athena
65from sqlglot.dialects.bigquery import BigQuery
66from sqlglot.dialects.clickhouse import ClickHouse
67from sqlglot.dialects.databricks import Databricks
68from sqlglot.dialects.dialect import Dialect, Dialects
69from sqlglot.dialects.doris import Doris
70from sqlglot.dialects.drill import Drill
71from sqlglot.dialects.druid import Druid
72from sqlglot.dialects.duckdb import DuckDB
73from sqlglot.dialects.hive import Hive
74from sqlglot.dialects.materialize import Materialize
75from sqlglot.dialects.mysql import MySQL
76from sqlglot.dialects.oracle import Oracle
77from sqlglot.dialects.postgres import Postgres
78from sqlglot.dialects.presto import Presto
79from sqlglot.dialects.prql import PRQL
80from sqlglot.dialects.redshift import Redshift
81from sqlglot.dialects.risingwave import RisingWave
82from sqlglot.dialects.snowflake import Snowflake
83from sqlglot.dialects.spark import Spark
84from sqlglot.dialects.spark2 import Spark2
85from sqlglot.dialects.sqlite import SQLite
86from sqlglot.dialects.starrocks import StarRocks
87from sqlglot.dialects.tableau import Tableau
88from sqlglot.dialects.teradata import Teradata
89from sqlglot.dialects.trino import Trino
90from sqlglot.dialects.tsql import TSQL