fix: use single quotes for SQL literals (PostgreSQL compatibility)

- condition.py: Use single quotes for string literals in WHERE clauses
  (double quotes are column identifiers in PostgreSQL)
- declare.py: Use single quotes for DEFAULT values
- dependencies.py: Escape % in LIKE patterns for psycopg2

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: dimitri-yatsenko

src/datajoint/condition.py

@@ -330,10 +330,12 @@ def prep_value(k, v):
                 list,
             ),
         ):
-            return f'{k}="{v}"'
+            # Use single quotes for string literals (works for both MySQL and PostgreSQL)
+            return f"{k}='{v}'"
         if isinstance(v, str):
-            v = v.replace("%", "%%").replace("\\", "\\\\")
-            return f'{k}="{v}"'
+            # Escape single quotes by doubling them, and escape % for driver
+            v = v.replace("'", "''").replace("%", "%%").replace("\\", "\\\\")
+            return f"{k}='{v}'"
         return f"{k}={v}"
 
     def combine_conditions(negate, conditions):

src/datajoint/declare.py

@@ -850,7 +850,8 @@ def compile_attribute(
     else:
         if match["default"]:
             quote = match["default"].split("(")[0].upper() not in CONSTANT_LITERALS and match["default"][0] not in "\"'"
-            match["default"] = "NOT NULL DEFAULT " + ('"%s"' if quote else "%s") % match["default"]
+            # Use single quotes for default values (works for both MySQL and PostgreSQL)
+            match["default"] = "NOT NULL DEFAULT " + ("'%s'" if quote else "%s") % match["default"]
         else:
             match["default"] = "NOT NULL"
 

src/datajoint/dependencies.py

@@ -169,7 +169,7 @@ def load(self, force: bool = True) -> None:
             # PostgreSQL
             tab_expr = "'\"' || table_schema || '\".\"' || table_name || '\"'"
             ref_tab_expr = "'\"' || referenced_table_schema || '\".\"' || referenced_table_name || '\"'"
-            like_pattern = "'~%'"  # PostgreSQL doesn't need escaping
+            like_pattern = "'~%%'"  # psycopg2 also uses %s placeholders, so escape %
 
         # load primary key info
         keys = self._conn.query(