diff --git a/Document/PG增加列.txt b/Document/PG增加列.txt
index 473d0603..6bc5f357 100644
--- a/Document/PG增加列.txt
+++ b/Document/PG增加列.txt
@@ -10,4 +10,8 @@ where  relkind = 'r' and relname like 'j%_r' and relname not like 'pg_%' and rel
 
 -- 设置默认值
 select 'DO $$  BEGIN   BEGIN   ALTER TABLE '||relname||' ALTER COLUMN recordyear  SET DEFAULT 2020;       EXCEPTION            WHEN duplicate_column THEN RAISE NOTICE ''column recordyear already exists'';   END; END;$$;'  as tabname from pg_class c 
-where  relkind = 'r' and relname like 'j%_r' and relname not like 'pg_%' and relname not like 'sql_%'  order by relname;
\ No newline at end of file
+where  relkind = 'r' and relname like 'j%_r' and relname not like 'pg_%' and relname not like 'sql_%'  order by relname;
+
+
+-- 删除默认值
+ALTER TABLE table_name ALTER COLUMN column_name DROP DEFAULT;
\ No newline at end of file