Db2 dialect added

README.md

@@ -1,6 +1,6 @@
 ![SQLGlot logo](sqlglot.png)
 
-SQLGlot is a no-dependency SQL parser, transpiler, optimizer, and engine. It can be used to format SQL or translate between [31 different dialects](https://github.com/tobymao/sqlglot/blob/main/sqlglot/dialects/__init__.py) like [DuckDB](https://duckdb.org/), [Presto](https://prestodb.io/) / [Trino](https://trino.io/), [Spark](https://spark.apache.org/) / [Databricks](https://www.databricks.com/), [Snowflake](https://www.snowflake.com/en/), and [BigQuery](https://cloud.google.com/bigquery/). It aims to read a wide variety of SQL inputs and output syntactically and semantically correct SQL in the targeted dialects.
+SQLGlot is a no-dependency SQL parser, transpiler, optimizer, and engine. It can be used to format SQL or translate between [32 different dialects](https://github.com/tobymao/sqlglot/blob/main/sqlglot/dialects/__init__.py) like [DuckDB](https://duckdb.org/), [Presto](https://prestodb.io/) / [Trino](https://trino.io/), [Spark](https://spark.apache.org/) / [Databricks](https://www.databricks.com/), [Snowflake](https://www.snowflake.com/en/), and [BigQuery](https://cloud.google.com/bigquery/). It aims to read a wide variety of SQL inputs and output syntactically and semantically correct SQL in the targeted dialects.
 
 It is a very comprehensive generic SQL parser with a robust [test suite](https://github.com/tobymao/sqlglot/blob/main/tests/). It is also quite [performant](#benchmarks), while being written purely in Python.
 
@@ -586,6 +586,7 @@ x + interval '1' month
 | BigQuery | Official |
 | ClickHouse | Official |
 | Databricks | Official |
+| Db2 | Community |
 | Doris | Community |
 | Dremio | Community |
 | Drill | Community |

sqlglot/dialects/__init__.py

@@ -69,6 +69,7 @@ class Generator(Generator):
     "BigQuery",
     "ClickHouse",
     "Databricks",
+    "Db2",
     "Doris",
     "Dremio",
     "Drill",

sqlglot/dialects/db2.py

@@ -0,0 +1,169 @@
+from __future__ import annotations
+
+import typing as t
+
+from sqlglot import exp, generator, tokens, transforms
+from sqlglot.dialects.dialect import (
+    Dialect,
+    NormalizationStrategy,
+    max_or_greatest,
+    min_or_least,
+    rename_func,
+    trim_sql,
+    no_ilike_sql,
+    no_pivot_sql,
+    no_trycast_sql,
+)
+from sqlglot.parsers.db2 import Db2Parser
+from sqlglot.tokens import TokenType
+
+if t.TYPE_CHECKING:
+    pass
+
+
+def _date_add_sql(
+    kind: str,
+) -> t.Callable[[Db2.Generator, exp.DateAdd | exp.DateSub], str]:
+    def func(self: Db2.Generator, expression: exp.DateAdd | exp.DateSub) -> str:
+        this = self.sql(expression, "this")
+        unit = expression.args.get("unit")
+        value = self._simplify_unless_literal(expression.expression)
+
+        if not isinstance(value, exp.Literal):
+            self.unsupported("Cannot add non literal")
+
+        value_sql = self.sql(value)
+        unit_sql = self.sql(unit) if unit else "DAY"
+
+        return f"{this} {kind} {value_sql} {unit_sql}"
+
+    return func
+
+
+class Db2(Dialect):
+    # DB2 is case-insensitive by default for unquoted identifiers
+    NORMALIZATION_STRATEGY = NormalizationStrategy.UPPERCASE
+
+    # DB2 supports NULL ordering
+    NULL_ORDERING = "nulls_are_large"
+
+    # DB2 specific settings
+    TYPED_DIVISION = True
+    SAFE_DIVISION = True
+
+    # Time format mappings for DB2
+    # https://www.ibm.com/docs/en/db2/11.5?topic=functions-timestamp-format
+    TIME_MAPPING = {
+        "YYYY": "%Y",
+        "YY": "%y",
+        "MM": "%m",
+        "DD": "%d",
+        "HH": "%H",
+        "HH12": "%I",
+        "HH24": "%H",
+        "MI": "%M",
+        "SS": "%S",
+        "FF": "%f",
+        "FF3": "%f",
+        "FF6": "%f",
+        "MON": "%b",
+        "MONTH": "%B",
+        "DY": "%a",
+        "DAY": "%A",
+    }
+
+    class Tokenizer(tokens.Tokenizer):
+        # DB2 uses @ for variables
+        VAR_SINGLE_TOKENS = {"@"}
+
+        # DB2 specific keywords
+        KEYWORDS = {
+            **tokens.Tokenizer.KEYWORDS,
+            "CHAR": TokenType.CHAR,
+            "CLOB": TokenType.TEXT,
+            "DBCLOB": TokenType.TEXT,
+            "DECFLOAT": TokenType.DECIMAL,
+            "GRAPHIC": TokenType.NCHAR,
+            "VARGRAPHIC": TokenType.NVARCHAR,
+            "SMALLINT": TokenType.SMALLINT,
+            "INTEGER": TokenType.INT,
+            "BIGINT": TokenType.BIGINT,
+            "REAL": TokenType.FLOAT,
+            "DOUBLE": TokenType.DOUBLE,
+            "DECIMAL": TokenType.DECIMAL,
+            "NUMERIC": TokenType.DECIMAL,
+            "VARCHAR": TokenType.VARCHAR,
+            "TIMESTAMP": TokenType.TIMESTAMP,
+            "TIMESTMP": TokenType.TIMESTAMP,
+            "SYSIBM": TokenType.SCHEMA,
+            "SYSFUN": TokenType.SCHEMA,
+            "SYSTOOLS": TokenType.SCHEMA,
+        }
+
+    Parser = Db2Parser
+
+    class Generator(generator.Generator):
+        LIMIT_FETCH = "FETCH"
+        JOIN_HINTS = False
+        TABLE_HINTS = False
+        QUERY_HINTS = False
+        NVL2_SUPPORTED = False
+        LAST_DAY_SUPPORTS_DATE_PART = False
+
+        # DB2 uses CONCAT operator
+        CONCAT_COALESCE = True
+
+        TYPE_MAPPING = {
+            **generator.Generator.TYPE_MAPPING,
+            exp.DataType.Type.BOOLEAN: "SMALLINT",
+            exp.DataType.Type.TINYINT: "SMALLINT",
+            exp.DataType.Type.BINARY: "BLOB",
+            exp.DataType.Type.VARBINARY: "BLOB",
+            exp.DataType.Type.TEXT: "CLOB",
+            exp.DataType.Type.NCHAR: "GRAPHIC",
+            exp.DataType.Type.NVARCHAR: "VARGRAPHIC",
+            exp.DataType.Type.TIMESTAMPTZ: "TIMESTAMP",
+            exp.DataType.Type.DATETIME: "TIMESTAMP",
+        }
+
+        TRANSFORMS = {
+            **generator.Generator.TRANSFORMS,
+            exp.ArgMax: rename_func("MAX"),
+            exp.ArgMin: rename_func("MIN"),
+            exp.DateAdd: _date_add_sql("+"),
+            exp.DateSub: _date_add_sql("-"),
+            exp.DateDiff: lambda self,
+            e: f"{self.func('DAYS', e.this)} - {self.func('DAYS', e.expression)}",
+            exp.CurrentDate: lambda self, e: "CURRENT DATE",
+            exp.CurrentTimestamp: lambda self, e: "CURRENT TIMESTAMP",
+            exp.ILike: no_ilike_sql,
+            exp.Max: max_or_greatest,
+            exp.Min: min_or_least,
+            exp.Pivot: no_pivot_sql,
+            exp.Select: transforms.preprocess([transforms.eliminate_distinct_on]),
+            exp.StrPosition: rename_func("POSSTR"),
+            exp.TimeToStr: rename_func("VARCHAR_FORMAT"),
+            exp.TryCast: no_trycast_sql,
+            exp.Trim: trim_sql,
+        }
+
+        def extract_sql(self, expression: exp.Extract) -> str:
+            this = self.sql(expression, "this")
+            expression_sql = self.sql(expression, "expression")
+
+            if this.upper() in ("DAYOFWEEK", "DAYOFYEAR"):
+                return f"{this.upper()}({expression_sql})"
+
+            return f"EXTRACT({this} FROM {expression_sql})"
+
+        def offset_sql(self, expression: exp.Offset) -> str:
+            return f"{super().offset_sql(expression)} ROWS"
+
+        def fetch_sql(self, expression: exp.Fetch) -> str:
+            count = expression.args.get("count")
+            if count:
+                return f" FETCH FIRST {self.sql(count)} ROWS ONLY"
+            return " FETCH FIRST ROW ONLY"
+
+        def boolean_sql(self, expression: exp.Boolean) -> str:
+            return "1" if expression.this else "0"

sqlglot/dialects/dialect.py

@@ -86,6 +86,7 @@ class Dialects(str, Enum):
     BIGQUERY = "bigquery"
     CLICKHOUSE = "clickhouse"
     DATABRICKS = "databricks"
+    DB2 = "db2"
     DORIS = "doris"
     DREMIO = "dremio"
     DRILL = "drill"

sqlglot/parsers/db2.py

@@ -0,0 +1,21 @@
+from __future__ import annotations
+
+from sqlglot import exp, parser
+from sqlglot.helper import seq_get
+
+
+class Db2Parser(parser.Parser):
+    FUNCTIONS = {
+        **parser.Parser.FUNCTIONS,
+        "CHAR": exp.Cast.from_arg_list,
+        "DAYOFWEEK": lambda args: exp.Extract(
+            this=exp.var("DAYOFWEEK"), expression=seq_get(args, 0)
+        ),
+        "DAYOFYEAR": lambda args: exp.Extract(
+            this=exp.var("DAYOFYEAR"), expression=seq_get(args, 0)
+        ),
+        "POSSTR": lambda args: exp.StrPosition(this=seq_get(args, 0), substr=seq_get(args, 1)),
+        "VARCHAR_FORMAT": lambda args: exp.TimeToStr(
+            this=seq_get(args, 0), format=seq_get(args, 1)
+        ),
+    }