Some fixes/improvements for sqlite

README.rst

@@ -1427,7 +1427,7 @@ This produces:
 Contributing
 ------------
 
-We welcome community contributions to |Brand|. Please see the `contributing guide <6_contributing.html>`_ to more info.
+We welcome community contributions to |Brand|. Please see the `contributing guide <CONTRIBUTING.rst>`_ to more info.
 
 .. _contributing_end:
 

pypika/dialects.py

@@ -950,7 +950,9 @@ class SQLLiteQueryBuilder(QueryBuilder):
     QUERY_CLS = SQLLiteQuery
 
     def __init__(self, **kwargs: Any) -> None:
-        super().__init__(dialect=Dialects.SQLLITE, wrapper_cls=SQLLiteValueWrapper, **kwargs)
+        if kwargs.get("wrapper_cls") is None:
+            kwargs["wrapper_cls"] = SQLLiteValueWrapper
+        super().__init__(dialect=Dialects.SQLLITE, **kwargs)
         self._insert_or_replace = False
 
     @builder
@@ -962,3 +964,15 @@ def insert_or_replace(self, *terms: Any) -> "SQLLiteQueryBuilder":
     def _replace_sql(self, **kwargs: Any) -> str:
         prefix = "INSERT OR " if self._insert_or_replace else ""
         return prefix + super()._replace_sql(**kwargs)
+
+    @builder
+    def for_update(
+        self, nowait: bool = False, skip_locked: bool = False, of: TypedTuple[str, ...] = ()
+    ) -> "QueryBuilder":
+        self._for_update = False
+
+    def _insert_sql(self, **kwargs: Any) -> str:
+        return "INSERT {ignore}INTO {table}".format(
+            table=self._insert_table.get_sql(**kwargs),
+            ignore="OR IGNORE " if self._ignore else "",
+        )

pypika/functions.py

@@ -265,6 +265,14 @@ class Now(Function):
     def __init__(self, alias=None):
         super(Now, self).__init__("NOW", alias=alias)
 
+    def get_function_sql(self, **kwargs):
+        # Handle SQLite compatibility - it uses CURRENT_TIMESTAMP instead of NOW()
+        from .enums import Dialects
+
+        if kwargs.get('dialect') == Dialects.SQLLITE:
+            return "CURRENT_TIMESTAMP"
+        return super(Now, self).get_function_sql(**kwargs)
+
 
 class UtcTimestamp(Function):
     def __init__(self, alias=None):

pypika/terms.py

@@ -1623,11 +1623,24 @@ class Interval(Node):
         # Oracle and MySQL requires just single quotes around the expr
         Dialects.ORACLE: "INTERVAL '{expr}' {unit}",
         Dialects.MYSQL: "INTERVAL '{expr}' {unit}",
+        # SQLite doesn't have a direct INTERVAL type, use datetime functions instead
+        Dialects.SQLLITE: "{expr} {unit}",
     }
 
     units = ["years", "months", "days", "hours", "minutes", "seconds", "microseconds"]
     labels = ["YEAR", "MONTH", "DAY", "HOUR", "MINUTE", "SECOND", "MICROSECOND"]
 
+    # SQLite unit conversion mapping
+    sqlite_units = {
+        "YEAR": "years",
+        "MONTH": "months",
+        "DAY": "days",
+        "HOUR": "hours",
+        "MINUTE": "minutes",
+        "SECOND": "seconds",
+        "MICROSECOND": "microseconds",
+    }
+
     trim_pattern = re.compile(r"(^0+\.)|(\.0+$)|(^[0\-.: ]+[\-: ])|([\-:. ][0\-.: ]+$)")
 
     def __init__(
@@ -1675,6 +1688,9 @@ def __str__(self) -> str:
     def get_sql(self, **kwargs: Any) -> str:
         dialect = self.dialect or kwargs.get("dialect")
 
+        if dialect == Dialects.SQLLITE:
+            return self._get_sqlite_sql()
+
         if self.largest == "MICROSECOND":
             expr = getattr(self, "microseconds")
             unit = "MICROSECOND"
@@ -1717,6 +1733,34 @@ def get_sql(self, **kwargs: Any) -> str:
 
         return self.templates.get(dialect, "INTERVAL '{expr} {unit}'").format(expr=expr, unit=unit)
 
+    def _get_sqlite_sql(self) -> str:
+        """Generate SQLite-compatible interval expression using datetime functions"""
+        if hasattr(self, "quarters"):
+            # Convert quarters to months for SQLite
+            value = getattr(self, "quarters") * 3
+            sign = "-" if self.is_negative else "+"
+            return f"datetime('now', '{sign}{value} months')"
+
+        if hasattr(self, "weeks"):
+            # Convert weeks to days for SQLite
+            value = getattr(self, "weeks") * 7
+            sign = "-" if self.is_negative else "+"
+            return f"datetime('now', '{sign}{value} days')"
+
+        # Construct datetime expression with each non-zero component
+        components = []
+        for unit, label in zip(self.units, self.labels):
+            if hasattr(self, unit) and getattr(self, unit):
+                value = getattr(self, unit)
+                sign = "-" if self.is_negative else "+"
+                sqlite_unit = self.sqlite_units.get(label, unit)
+                components.append(f"'{sign}{value} {sqlite_unit}'")
+
+        if not components:
+            return "datetime('now')"
+
+        return f"datetime('now', {', '.join(components)})"
+
 
 class Pow(Function):
     def __init__(self, term: Term, exponent: float, alias: Optional[str] = None) -> None: