Implement CASCADE behavior enforcement for FOREIGN KEY constraints #2336

AlaSQL currently parses CASCADE syntax but does not enforce the behavior. When a parent row is deleted or updated, child rows with ON DELETE CASCADE or ON UPDATE CASCADE are not automatically affected.

What needs to be implemented

ON DELETE actions:

• CASCADE: When a row in the parent table is deleted, automatically delete all rows in child tables that reference it
• SET NULL: Set foreign key columns to NULL in child tables when parent is deleted
• SET DEFAULT: Set foreign key columns to their default value when parent is deleted
• RESTRICT: Prevent deletion of parent row if child rows exist
• NO ACTION: Same as RESTRICT per SQL-99 standard

ON UPDATE actions:

• CASCADE: When parent key is updated, update matching foreign keys in child tables
• SET NULL: Set foreign key to NULL when parent key is updated
• SET DEFAULT: Set foreign key to default when parent key is updated
• RESTRICT: Prevent update of parent key if child rows exist
• NO ACTION: Same as RESTRICT per SQL-99 standard

Implementation areas

• Modify DELETE statement handler (src/74delete.js) to check for child tables and apply CASCADE actions
• Modify UPDATE statement handler (src/74update.js) to check for child tables and apply CASCADE actions
• Store foreign key metadata including ondelete/onupdate actions in table definition during CREATE TABLE
• Add validation for RESTRICT actions before allowing delete/update
• Handle circular dependencies and prevent infinite loops

Related

• Fixes parsing: CASCADE not supported (sqlite)  #897
• Parser support added in: PR Add parser support for ON DELETE and ON UPDATE CASCADE in REFERENCES #2311