diff --git a/CN/modules/ROOT/nav.adoc b/CN/modules/ROOT/nav.adoc
index b62fe4a5..ce0d05d5 100644
--- a/CN/modules/ROOT/nav.adoc
+++ b/CN/modules/ROOT/nav.adoc
@@ -1,127 +1,129 @@
-* xref:master/about_ivorysql.adoc[关于IvorySQL]
-** xref:master/welcome.adoc[欢迎]
-** xref:master/release_notes.adoc[发行说明]
-* 快速上手
-** xref:master/getting-started/quick_start.adoc[快速开始]
-* 安装部署
-** xref:master/installation_guide.adoc[安装指南]
-** xref:master/cluster_setup.adoc[集群搭建]
-* Oracle兼容功能
-** xref:master/oracle_compatibility/compat_case_conversion.adoc[1、大小写转换]
-** xref:master/oracle_compatibility/compat_like_operator.adoc[2、LIKE操作符]
-** xref:master/oracle_compatibility/anonymous_block.adoc[3、匿名块]
-** xref:master/oracle_compatibility/compat_function_procedure.adoc[4、函数与存储过程]
-** xref:master/oracle_compatibility/builtin_types_functions.adoc[5、内置数据类型与内置函数]
-** xref:master/oracle_compatibility/port_ip.adoc[6、端口与IP]
-** xref:master/oracle_compatibility/xml_functions.adoc[7、XML函数]
-** xref:master/oracle_compatibility/sequence.adoc[8、sequence]
-** xref:master/oracle_compatibility/package.adoc[9、包]
-** xref:master/oracle_compatibility/invisible_column.adoc[10、不可见列]
-** xref:master/oracle_compatibility/compat_rowid.adoc[11、RowID]
-** xref:master/oracle_compatibility/compat_out_parameter.adoc[12、OUT 参数]
-** xref:master/oracle_compatibility/compat_type_rowtype.adoc[13、%TYPE、%ROWTYPE]
-** xref:master/oracle_compatibility/compat_nls_parameter.adoc[14、NLS 参数]
-** xref:master/oracle_compatibility/compat_force_view.adoc[15、Force View]
-** xref:master/oracle_compatibility/compat_nested_function.adoc[16、嵌套子函数]
-** xref:master/oracle_compatibility/compat_sys_guid.adoc[17、sys_guid 函数]
-** xref:master/oracle_compatibility/compat_empty_string_to_null.adoc[18、空字符串转null]
-** xref:master/oracle_compatibility/compat_call_into.adoc[19、CALL INTO]
-** xref:master/oracle_compatibility/compat_read_only_view.adoc[20、视图只读]
-** xref:master/oracle_compatibility/with_function_procedure.adoc[21、WITH FUNCTION/PROCEDURE]
-** xref:master/oracle_compatibility/compat_create_index_online.adoc[22、索引 ONLINE 参数]
-** xref:master/oracle_compatibility/compat_stragg.adoc[23、STRAGG 函数]
-** xref:master/oracle_compatibility/compat_alter_index_unusable.adoc[24、禁用索引]
-** xref:master/oracle_compatibility/compat_dbtimezone.adoc[25、dbtimezone]
-* 容器化与云服务
-** 容器化指南
-*** xref:master/containerization/k8s_deployment.adoc[K8S部署]
-*** xref:master/containerization/operator_deployment.adoc[Operator部署]
-*** xref:master/containerization/docker_podman_deployment.adoc[Docker & Podman部署]
-*** xref:master/containerization/docker_swarm_compose_deployment.adoc[Docker Swarm & Docker Compose部署]
-** 云服务平台指南
-*** xref:master/cloud_platform/ivorysql_cloud_installation.adoc[IvorySQL Cloud安装]
-*** xref:master/cloud_platform/ivorysql_cloud_usage.adoc[IvorySQL Cloud使用]
-* IvorySQL生态
-** xref:master/cpu_os_adaptation/cpu_architecture_adaptation.adoc[芯片架构适配]
-** xref:master/cpu_os_adaptation/os_architecture_adaptation.adoc[操作系统适配]
-** 生态组件适配
-*** xref:master/ecosystem_components/ecosystem_overview.adoc[概述]
-*** xref:master/ecosystem_components/postgis.adoc[postgis]
-*** xref:master/ecosystem_components/pgvector.adoc[pgvector]
-*** xref:master/ecosystem_components/pgddl.adoc[pgddl(DDL Extractor)]
-*** xref:master/ecosystem_components/pg_cron.adoc[pg_cron]
-*** xref:master/ecosystem_components/pgsql_http.adoc[pgsql-http]
-*** xref:master/ecosystem_components/plpgsql_check.adoc[plpgsql_check]
-*** xref:master/ecosystem_components/pgroonga.adoc[pgroonga]
-*** xref:master/ecosystem_components/pgaudit.adoc[pgaudit]
-*** xref:master/ecosystem_components/pgrouting.adoc[pgrouting]
-*** xref:master/ecosystem_components/system_stats.adoc[system_stats]
-*** xref:master/ecosystem_components/wal2json.adoc[wal2json]
-*** xref:master/ecosystem_components/pg_stat_monitor.adoc[pg_stat_monitor]
-*** xref:master/ecosystem_components/pg_ai_query.adoc[pg_ai_query]
-*** xref:master/ecosystem_components/pg_partman.adoc[pg_partman]
-*** xref:master/ecosystem_components/pgbouncer.adoc[pgbouncer]
-*** xref:master/ecosystem_components/age.adoc[age]
-*** xref:master/ecosystem_components/pg_curl.adoc[pg_curl]
-*** xref:master/ecosystem_components/pg_textsearch.adoc[pg_textsearch]
-*** xref:master/ecosystem_components/pg_hint_plan.adoc[pg_hint_plan]
-*** xref:master/ecosystem_components/redis_fdw.adoc[redis_fdw]
-*** xref:master/ecosystem_components/pg_show_plans.adoc[pg_show_plans]
-*** xref:master/ecosystem_components/pg_bulkload.adoc[pg_bulkload]
-*** xref:master/ecosystem_components/pg_bigm.adoc[pg_bigm]
-*** xref:master/ecosystem_components/pg_profile.adoc[pg_profile]
-*** xref:master/ecosystem_components/pg_repack.adoc[pg_repack]
-*** xref:master/ecosystem_components/pgdog.adoc[PgDog]
-*** xref:master/ecosystem_components/pg_readonly.adoc[pg_readonly]
-*** xref:master/ecosystem_components/zhparser.adoc[zhparser]
-*** xref:master/ecosystem_components/pgbackrest.adoc[pgBackRest]
-*** xref:master/ecosystem_components/set_user.adoc[set_user]
-* 监控运维
-** xref:master/getting-started/daily_monitoring.adoc[日常监控]
-** xref:master/getting-started/daily_maintenance.adoc[日常维护]
-** xref:master/operation_guide.adoc[运维管理指南]
-* 数据迁移
-** xref:master/migration_guide.adoc[迁移指南]
-* IvorySQL开发者
-** xref:master/contribution/contribution_guide.adoc[贡献指南]
-** xref:master/developer_guide.adoc[开发者指南]
-** IvorySQL架构设计
-*** 查询处理
-**** xref:master/architecture/dual_parser.adoc[双parser]
-*** 兼容框架
-**** xref:master/architecture/framework_design.adoc[框架设计]
-**** xref:master/architecture/guc_framework.adoc[GUC框架]
-**** xref:master/architecture/dual_mode_design.adoc[双模式设计]
-**** xref:master/architecture/initdb_process.adoc[initdb过程]
-*** 兼容特性
-**** xref:master/compatibility_features_design/like_operator.adoc[like]
-**** xref:master/compatibility_features_design/rowid.adoc[RowID]
-**** xref:master/compatibility_features_design/out_parameter.adoc[OUT 参数]
-**** xref:master/compatibility_features_design/type_rowtype.adoc[%TYPE、%ROWTYPE]
-**** xref:master/compatibility_features_design/nls_parameter.adoc[NLS 参数]
-**** xref:master/compatibility_features_design/function_procedure.adoc[函数与存储过程]
-**** xref:master/compatibility_features_design/nested_function.adoc[嵌套子函数]
-**** xref:master/compatibility_features_design/force_view.adoc[Force View]
-**** xref:master/compatibility_features_design/case_conversion.adoc[大小写转换]
-**** xref:master/compatibility_features_design/sys_guid_function.adoc[sys_guid 函数]
-**** xref:master/compatibility_features_design/empty_string_to_null.adoc[空字符串转null]
-**** xref:master/compatibility_features_design/call_into.adoc[CALL INTO]
-**** xref:master/compatibility_features_design/read_only_view.adoc[视图只读]
-**** xref:master/compatibility_features_design/with_function_procedure_impl.adoc[WITH FUNCTION/PROCEDURE]
-**** xref:master/compatibility_features_design/create_index_online.adoc[索引 ONLINE 参数]
-**** xref:master/compatibility_features_design/alter_index_unusable_impl.adoc[禁用索引]
-*** 内置函数
-**** xref:master/oracle_builtin_functions/sys_context.adoc[sys_context]
-**** xref:master/oracle_builtin_functions/userenv.adoc[userenv]
-**** xref:master/oracle_builtin_functions/rawtohex.adoc[rawtohex]
-**** xref:master/oracle_builtin_functions/stragg.adoc[stragg]
-**** xref:master/oracle_builtin_functions/dbtimezone_impl.adoc[dbtimezone]
-*** xref:master/gb18030.adoc[国标GB18030]
-* 参考指南
-** xref:master/tools_reference.adoc[工具参考]
-** xref:master/contribution/asciidoc_syntax_reference.adoc[asciidoc语法快速参考]
-** xref:master/pg_reference/pg_parameters_reference.adoc[PG参数参考手册]
-** xref:master/pg_reference/pg_functions_reference.adoc[PG函数参考手册]
-* 常见问题解答
-** xref:master/contribution/faq.adoc[FAQ]
-
+* xref:master/about_ivorysql.adoc[关于IvorySQL]
+** xref:master/welcome.adoc[欢迎]
+** xref:master/release_notes.adoc[发行说明]
+* 快速上手
+** xref:master/getting-started/quick_start.adoc[快速开始]
+* 安装部署
+** xref:master/installation_guide.adoc[安装指南]
+** xref:master/cluster_setup.adoc[集群搭建]
+* Oracle兼容功能
+** xref:master/oracle_compatibility/compat_case_conversion.adoc[1、大小写转换]
+** xref:master/oracle_compatibility/compat_like_operator.adoc[2、LIKE操作符]
+** xref:master/oracle_compatibility/anonymous_block.adoc[3、匿名块]
+** xref:master/oracle_compatibility/compat_function_procedure.adoc[4、函数与存储过程]
+** xref:master/oracle_compatibility/builtin_types_functions.adoc[5、内置数据类型与内置函数]
+** xref:master/oracle_compatibility/port_ip.adoc[6、端口与IP]
+** xref:master/oracle_compatibility/xml_functions.adoc[7、XML函数]
+** xref:master/oracle_compatibility/sequence.adoc[8、sequence]
+** xref:master/oracle_compatibility/package.adoc[9、包]
+** xref:master/oracle_compatibility/invisible_column.adoc[10、不可见列]
+** xref:master/oracle_compatibility/compat_rowid.adoc[11、RowID]
+** xref:master/oracle_compatibility/compat_out_parameter.adoc[12、OUT 参数]
+** xref:master/oracle_compatibility/compat_type_rowtype.adoc[13、%TYPE、%ROWTYPE]
+** xref:master/oracle_compatibility/compat_nls_parameter.adoc[14、NLS 参数]
+** xref:master/oracle_compatibility/compat_force_view.adoc[15、Force View]
+** xref:master/oracle_compatibility/compat_nested_function.adoc[16、嵌套子函数]
+** xref:master/oracle_compatibility/compat_sys_guid.adoc[17、sys_guid 函数]
+** xref:master/oracle_compatibility/compat_empty_string_to_null.adoc[18、空字符串转null]
+** xref:master/oracle_compatibility/compat_call_into.adoc[19、CALL INTO]
+** xref:master/oracle_compatibility/compat_read_only_view.adoc[20、视图只读]
+** xref:master/oracle_compatibility/with_function_procedure.adoc[21、WITH FUNCTION/PROCEDURE]
+** xref:master/oracle_compatibility/compat_create_index_online.adoc[22、索引 ONLINE 参数]
+** xref:master/oracle_compatibility/compat_stragg.adoc[23、STRAGG 函数]
+** xref:master/oracle_compatibility/compat_alter_index_unusable.adoc[24、禁用索引]
+** xref:master/oracle_compatibility/compat_dbtimezone.adoc[25、dbtimezone]
+** xref:master/oracle_compatibility/compat_lnnvl.adoc[26、LNNVL 函数]
+* 容器化与云服务
+** 容器化指南
+*** xref:master/containerization/k8s_deployment.adoc[K8S部署]
+*** xref:master/containerization/operator_deployment.adoc[Operator部署]
+*** xref:master/containerization/docker_podman_deployment.adoc[Docker & Podman部署]
+*** xref:master/containerization/docker_swarm_compose_deployment.adoc[Docker Swarm & Docker Compose部署]
+** 云服务平台指南
+*** xref:master/cloud_platform/ivorysql_cloud_installation.adoc[IvorySQL Cloud安装]
+*** xref:master/cloud_platform/ivorysql_cloud_usage.adoc[IvorySQL Cloud使用]
+* IvorySQL生态
+** xref:master/cpu_os_adaptation/cpu_architecture_adaptation.adoc[芯片架构适配]
+** xref:master/cpu_os_adaptation/os_architecture_adaptation.adoc[操作系统适配]
+** 生态组件适配
+*** xref:master/ecosystem_components/ecosystem_overview.adoc[概述]
+*** xref:master/ecosystem_components/postgis.adoc[postgis]
+*** xref:master/ecosystem_components/pgvector.adoc[pgvector]
+*** xref:master/ecosystem_components/pgddl.adoc[pgddl(DDL Extractor)]
+*** xref:master/ecosystem_components/pg_cron.adoc[pg_cron]
+*** xref:master/ecosystem_components/pgsql_http.adoc[pgsql-http]
+*** xref:master/ecosystem_components/plpgsql_check.adoc[plpgsql_check]
+*** xref:master/ecosystem_components/pgroonga.adoc[pgroonga]
+*** xref:master/ecosystem_components/pgaudit.adoc[pgaudit]
+*** xref:master/ecosystem_components/pgrouting.adoc[pgrouting]
+*** xref:master/ecosystem_components/system_stats.adoc[system_stats]
+*** xref:master/ecosystem_components/wal2json.adoc[wal2json]
+*** xref:master/ecosystem_components/pg_stat_monitor.adoc[pg_stat_monitor]
+*** xref:master/ecosystem_components/pg_ai_query.adoc[pg_ai_query]
+*** xref:master/ecosystem_components/pg_partman.adoc[pg_partman]
+*** xref:master/ecosystem_components/pgbouncer.adoc[pgbouncer]
+*** xref:master/ecosystem_components/age.adoc[age]
+*** xref:master/ecosystem_components/pg_curl.adoc[pg_curl]
+*** xref:master/ecosystem_components/pg_textsearch.adoc[pg_textsearch]
+*** xref:master/ecosystem_components/pg_hint_plan.adoc[pg_hint_plan]
+*** xref:master/ecosystem_components/redis_fdw.adoc[redis_fdw]
+*** xref:master/ecosystem_components/pg_show_plans.adoc[pg_show_plans]
+*** xref:master/ecosystem_components/pg_bulkload.adoc[pg_bulkload]
+*** xref:master/ecosystem_components/pg_bigm.adoc[pg_bigm]
+*** xref:master/ecosystem_components/pg_profile.adoc[pg_profile]
+*** xref:master/ecosystem_components/pg_repack.adoc[pg_repack]
+*** xref:master/ecosystem_components/pgdog.adoc[PgDog]
+*** xref:master/ecosystem_components/pg_readonly.adoc[pg_readonly]
+*** xref:master/ecosystem_components/zhparser.adoc[zhparser]
+*** xref:master/ecosystem_components/pgbackrest.adoc[pgBackRest]
+*** xref:master/ecosystem_components/set_user.adoc[set_user]
+* 监控运维
+** xref:master/getting-started/daily_monitoring.adoc[日常监控]
+** xref:master/getting-started/daily_maintenance.adoc[日常维护]
+** xref:master/operation_guide.adoc[运维管理指南]
+* 数据迁移
+** xref:master/migration_guide.adoc[迁移指南]
+* IvorySQL开发者
+** xref:master/contribution/contribution_guide.adoc[贡献指南]
+** xref:master/developer_guide.adoc[开发者指南]
+** IvorySQL架构设计
+*** 查询处理
+**** xref:master/architecture/dual_parser.adoc[双parser]
+*** 兼容框架
+**** xref:master/architecture/framework_design.adoc[框架设计]
+**** xref:master/architecture/guc_framework.adoc[GUC框架]
+**** xref:master/architecture/dual_mode_design.adoc[双模式设计]
+**** xref:master/architecture/initdb_process.adoc[initdb过程]
+*** 兼容特性
+**** xref:master/compatibility_features_design/like_operator.adoc[like]
+**** xref:master/compatibility_features_design/rowid.adoc[RowID]
+**** xref:master/compatibility_features_design/out_parameter.adoc[OUT 参数]
+**** xref:master/compatibility_features_design/type_rowtype.adoc[%TYPE、%ROWTYPE]
+**** xref:master/compatibility_features_design/nls_parameter.adoc[NLS 参数]
+**** xref:master/compatibility_features_design/function_procedure.adoc[函数与存储过程]
+**** xref:master/compatibility_features_design/nested_function.adoc[嵌套子函数]
+**** xref:master/compatibility_features_design/force_view.adoc[Force View]
+**** xref:master/compatibility_features_design/case_conversion.adoc[大小写转换]
+**** xref:master/compatibility_features_design/sys_guid_function.adoc[sys_guid 函数]
+**** xref:master/compatibility_features_design/empty_string_to_null.adoc[空字符串转null]
+**** xref:master/compatibility_features_design/call_into.adoc[CALL INTO]
+**** xref:master/compatibility_features_design/read_only_view.adoc[视图只读]
+**** xref:master/compatibility_features_design/with_function_procedure_impl.adoc[WITH FUNCTION/PROCEDURE]
+**** xref:master/compatibility_features_design/create_index_online.adoc[索引 ONLINE 参数]
+**** xref:master/compatibility_features_design/alter_index_unusable_impl.adoc[禁用索引]
+*** 内置函数
+**** xref:master/oracle_builtin_functions/sys_context.adoc[sys_context]
+**** xref:master/oracle_builtin_functions/userenv.adoc[userenv]
+**** xref:master/oracle_builtin_functions/rawtohex.adoc[rawtohex]
+**** xref:master/oracle_builtin_functions/stragg.adoc[stragg]
+**** xref:master/oracle_builtin_functions/dbtimezone_impl.adoc[dbtimezone]
+**** xref:master/oracle_builtin_functions/lnnvl.adoc[lnnvl]
+*** xref:master/gb18030.adoc[国标GB18030]
+* 参考指南
+** xref:master/tools_reference.adoc[工具参考]
+** xref:master/contribution/asciidoc_syntax_reference.adoc[asciidoc语法快速参考]
+** xref:master/pg_reference/pg_parameters_reference.adoc[PG参数参考手册]
+** xref:master/pg_reference/pg_functions_reference.adoc[PG函数参考手册]
+* 常见问题解答
+** xref:master/contribution/faq.adoc[FAQ]
+
diff --git a/CN/modules/ROOT/pages/master/oracle_builtin_functions/lnnvl.adoc b/CN/modules/ROOT/pages/master/oracle_builtin_functions/lnnvl.adoc
new file mode 100644
index 00000000..58c51111
--- /dev/null
+++ b/CN/modules/ROOT/pages/master/oracle_builtin_functions/lnnvl.adoc
@@ -0,0 +1,131 @@
+:sectnums:
+:sectnumlevels: 5
+
+:imagesdir: ./_images
+
+= LNNVL 函数的实现
+
+== 目的
+
+IvorySQL 在 `contrib/ivorysql_ora` 扩展中新增 `sys.lnnvl(boolean)` 函数，
+实现与 Oracle 同名函数一致的条件取反行为：条件求值为 FALSE 或 UNKNOWN 时返回 TRUE，
+求值为 TRUE 时返回 FALSE。
+
+== 实现说明
+
+=== 语义等价于 IS NOT TRUE
+
+LNNVL 的真值表与 SQL 标准的 `IS NOT TRUE` 谓词逐格相同：
+
+[cols="1,1,1"]
+|===
+|条件求值结果 |`LNNVL(cond)` |`cond IS NOT TRUE`
+
+|TRUE
+|FALSE
+|FALSE
+
+|FALSE
+|TRUE
+|TRUE
+
+|UNKNOWN
+|TRUE
+|TRUE
+|===
+
+因此实现无需新增任何求值逻辑，函数体只是这一个谓词。
+PostgreSQL 中 `IS NOT TRUE` 的求值位于
+`src/backend/executor/execExprInterp.c` 的 `EEOP_BOOLTEST_IS_NOT_TRUE` 分支，
+入参为 NULL 时直接返回 true 并清除结果的 null 标记，
+因此 LNNVL 自身永不返回 NULL。
+
+=== SQL 定义
+
+函数定义位于
+`contrib/ivorysql_ora/src/builtin_functions/builtin_functions--1.0.sql`。
+
+[source,sql]
+----
+CREATE FUNCTION sys.lnnvl(pg_catalog.bool)
+RETURNS pg_catalog.bool
+AS $$SELECT $1 IS NOT TRUE$$
+LANGUAGE sql
+CALLED ON NULL INPUT
+PARALLEL SAFE
+IMMUTABLE;
+----
+
+各项属性的选择理由：
+
+[cols="1,1,3"]
+|===
+|属性 |取值 |理由
+
+|所在模式
+|`sys`
+|与其它 Oracle 兼容函数一致。`sys` 仅在 Oracle 兼容模式下进入隐式 `search_path`。
+
+|参数类型
+|`pg_catalog.bool`
+|显式限定模式，避免 Oracle 模式下 `sys` 位于 `search_path` 首位时类型名解析受影响。
+
+|语言
+|`sql`
+|可被 `inline_function()` 内联，见下节。C 函数不会被内联。
+
+|NULL 处理
+|`CALLED ON NULL INPUT`
+|必须项，见下节。
+
+|易变性
+|`IMMUTABLE`
+|纯逻辑运算，同一输入恒定输出；也是用于表达式索引等场景的前提。
+
+|并行性
+|`PARALLEL SAFE`
+|无副作用。若不声明，默认为 `PARALLEL UNSAFE`，会禁用相关查询的并行计划。
+|===
+
+=== CALLED ON NULL INPUT 是必须项
+
+`CALLED ON NULL INPUT` 是 SQL 的默认值，此处显式写出是为了防止被误改。
+
+若声明为 `STRICT`，入参为 NULL 时函数体根本不会执行，直接返回 NULL，
+而正确行为是返回 TRUE —— 恰好毁掉 LNNVL 存在的唯一理由，且不产生任何错误。
+风险来自代码风格的一致性压力：`builtin_functions--1.0.sql` 中多数邻近函数均声明为
+`STRICT`，按邻居样式统一即会踩中。
+
+`STRICT` 还会连带废掉内联。声明为严格意味着承诺"NULL 进则 NULL 出"，
+而 `IS NOT TRUE` 本身并非严格谓词，优化器无法在保持语义的前提下将其展开，
+只能保留函数调用：
+
+[source,text]
+----
+-- CALLED ON NULL INPUT
+Filter: (t.v IS NOT TRUE)
+
+-- STRICT
+Filter: f_strict(t.v)
+----
+
+因此误写为 `STRICT` 是双重损失：语义错误且静默，同时性能退化为逐行函数调用。
+
+=== 函数内联
+
+函数体是可内联的简单 SQL 表达式，优化器的 `inline_function()` 会将其折叠到调用处：
+
+[source,sql]
+----
+EXPLAIN (VERBOSE, COSTS OFF) SELECT id FROM t WHERE LNNVL(v >= 0.2);
+----
+
+[source,text]
+----
+ Seq Scan on public.t
+   Output: id
+   Filter: ((t.v >= 0.2) IS NOT TRUE)
+----
+
+计划中已不存在函数调用，与用户直接书写 `IS NOT TRUE` 的计划逐字相同，
+因此不引入额外运行期开销。
diff --git a/CN/modules/ROOT/pages/master/oracle_compatibility/compat_lnnvl.adoc b/CN/modules/ROOT/pages/master/oracle_compatibility/compat_lnnvl.adoc
new file mode 100644
index 00000000..88a815ba
--- /dev/null
+++ b/CN/modules/ROOT/pages/master/oracle_compatibility/compat_lnnvl.adoc
@@ -0,0 +1,253 @@
+:sectnums:
+:sectnumlevels: 5
+
+:imagesdir: ./_images
+
+= LNNVL 函数
+
+== 目的
+
+本文档说明 IvorySQL 中 `sys.lnnvl` 函数的功能，该函数以兼容 Oracle 的方式
+对条件取反，并且在条件求值结果为 UNKNOWN 时仍然返回 TRUE。
+
+== 功能说明
+
+* `sys.lnnvl(boolean)` 接受一个条件，条件求值为 FALSE 或 UNKNOWN 时返回 TRUE，
+  求值为 TRUE 时返回 FALSE。
+* 函数**永不返回 NULL**，返回值必为 TRUE 或 FALSE 之一，
+  因此可以直接用作 WHERE 条件而不会引入新的 UNKNOWN。
+* 主要用途是消除三值逻辑造成的"行丢失"：直接书写 `NOT` 时，
+  条件为 UNKNOWN 的行在原条件和取反条件下都会被丢弃；
+  而条件与其 LNNVL 构成对整表的严格划分，两者的结果行数之和恒等于总行数。
+
+真值表：
+
+[cols="1,1"]
+|===
+|条件求值结果 |返回值
+
+|TRUE
+|FALSE
+
+|FALSE
+|TRUE
+
+|UNKNOWN（条件中含 NULL）
+|TRUE
+|===
+
+== 语法
+
+[source,sql]
+----
+sys.lnnvl(condition)
+----
+
+[cols="1,3"]
+|===
+|参数 |说明
+
+|`condition`
+|任意布尔表达式。不接受非布尔类型，且不存在从整型的隐式转换。
+|===
+
+返回类型：`boolean`
+
+== 测试用例
+
+=== 测试环境准备
+
+[source,sql]
+----
+CREATE TABLE lnnvl_test (a INT, b INT);
+INSERT INTO lnnvl_test VALUES (2, NULL);
+----
+
+=== 真值表验证
+
+[source,sql]
+----
+-- a = 2，b 为 NULL
+SELECT LNNVL(a = 1) FROM lnnvl_test;        -- 期望：t（条件为 FALSE）
+SELECT LNNVL(a = 2) FROM lnnvl_test;        -- 期望：f（条件为 TRUE）
+SELECT LNNVL(a IS NULL) FROM lnnvl_test;    -- 期望：t（条件为 FALSE）
+SELECT LNNVL(b = 1) FROM lnnvl_test;        -- 期望：t（条件为 UNKNOWN）
+SELECT LNNVL(b IS NULL) FROM lnnvl_test;    -- 期望：f（条件为 TRUE）
+SELECT LNNVL(a = b) FROM lnnvl_test;        -- 期望：t（条件为 UNKNOWN）
+----
+
+=== NULL 入参
+
+[source,sql]
+----
+-- NULL 入参必须返回 t，这是 LNNVL 的核心行为
+SELECT LNNVL(NULL);                         -- 期望：t
+SELECT LNNVL(NULL::boolean);                -- 期望：t
+----
+
+=== 划分性质
+
+[source,sql]
+----
+DROP TABLE lnnvl_test;
+CREATE TABLE lnnvl_test (id INT, v NUMERIC);
+INSERT INTO lnnvl_test VALUES (1,0.30),(2,0.10),(3,NULL),(4,0.25),(5,NULL);
+
+SELECT count(*) FROM lnnvl_test WHERE v >= 0.2;          -- 期望：2
+SELECT count(*) FROM lnnvl_test WHERE LNNVL(v >= 0.2);   -- 期望：3
+SELECT count(*) FROM lnnvl_test;                         -- 期望：5
+
+-- 2 + 3 = 5，条件与其 LNNVL 覆盖全表，无行丢失
+-- 若改用 NOT，两者之和会小于总行数
+SELECT count(*) FROM lnnvl_test WHERE NOT (v >= 0.2);    -- 期望：2，合计仅 4
+----
+
+=== NOT IN 遇含 NULL 的子查询
+
+[source,sql]
+----
+CREATE TABLE lnnvl_bl (d INT);
+INSERT INTO lnnvl_bl VALUES (1), (NULL);
+
+-- 黑名单含 NULL 时，NOT IN 返回空集
+SELECT count(*) FROM lnnvl_test WHERE id NOT IN (SELECT d FROM lnnvl_bl);
+-- 期望：0
+
+-- 改写为 LNNVL(... IN ...) 后得到符合直觉的结果
+SELECT count(*) FROM lnnvl_test WHERE LNNVL(id IN (SELECT d FROM lnnvl_bl));
+-- 期望：4
+----
+
+`id NOT IN (1, NULL)` 展开为 `id <> 1 AND id <> NULL`，
+其中 `id <> NULL` 恒为 UNKNOWN，导致整个条件不为 TRUE，因此所有行都被丢弃。
+`LNNVL(id IN (...))` 把 UNKNOWN 判定为"非真"从而保留这些行。
+
+=== 参数类型检查
+
+[source,sql]
+----
+-- 参数必须是布尔类型，不存在从整型的隐式转换
+SELECT LNNVL(1);
+-- 期望报错：function lnnvl(pg_catalog.int4) does not exist
+----
+
+=== 测试环境清理
+
+[source,sql]
+----
+DROP TABLE lnnvl_bl;
+DROP TABLE lnnvl_test;
+----
+
+== 与 Oracle 的行为差异
+
+Oracle 的语法只接受单个简单条件。IvorySQL 以普通函数实现，
+参数在重载决议时已经是一个布尔表达式，产生它的 `AND`、`OR`、`NOT`、`BETWEEN`
+对函数不可见，因此无法复现 Oracle 的形态限制，**接受的形态是 Oracle 的超集**。
+
+方向性结论：能在 Oracle 上运行的 LNNVL 写法在 IvorySQL 上一定能运行；
+反之不保证 —— 在 IvorySQL 上写通的复合条件形式搬回 Oracle 会报错。
+
+[cols="2,1,1"]
+|===
+|参数形态 |Oracle |IvorySQL
+
+|`LNNVL(1 = 1 AND 2 = 2)`
+|拒绝
+|接受，返回 f
+
+|`LNNVL(1 = 1 OR 2 = 2)`
+|拒绝
+|接受，返回 f
+
+|`LNNVL(1 BETWEEN 0 AND 5)`
+|拒绝
+|接受，返回 f
+
+|`LNNVL(1 NOT BETWEEN 0 AND 5)`
+|拒绝
+|接受，返回 t
+
+|`LNNVL(NOT (1 = 1))`
+|拒绝（ORA-00936）
+|接受，返回 t
+
+|`LNNVL(NOT EXISTS (SELECT ...))`
+|拒绝（ORA-00936）
+|接受，返回 t
+
+|`LNNVL(1 IN (1,2))`
+|拒绝（ORA-13207）
+|接受，返回 f
+
+|`LNNVL(1 NOT IN (1,2))`
+|拒绝（ORA-13207）
+|接受，返回 t
+|===
+
+其它差异：
+
+[cols="1,2,2"]
+|===
+|场景 |Oracle |IvorySQL
+
+|错误码与错误文本
+|`ORA-` 编号
+|PostgreSQL 的 SQLSTATE 与英文描述
+
+|`LNNVL(1)`
+|依据其 BOOLEAN 类型转换规则处理
+|报函数不存在，不做隐式转换
+|===
+
+需要表达复合条件时，按 Oracle 的做法拆成多个 LNNVL 调用再用 `AND` 或 `OR` 连接：
+
+[source,sql]
+----
+SELECT LNNVL(1 = 1) OR LNNVL(2 = 3);    -- 期望：f
+SELECT LNNVL(1 = 1) AND LNNVL(2 = 3);   -- 期望：f
+SELECT NOT LNNVL(1 = 1);                -- 期望：t
+----
+
+注意拆分时需遵循德摩根律：`LNNVL(A AND B)` 语义上对应
+`LNNVL(A) OR LNNVL(B)`，写成 `AND` 会改变结果。
+
+== 与 NOT 的比较
+
+[cols="1,2,2"]
+|===
+|条件求值结果 |`NOT cond` |`LNNVL(cond)`
+
+|TRUE
+|FALSE
+|FALSE
+
+|FALSE
+|TRUE
+|TRUE
+
+|UNKNOWN
+|UNKNOWN（行被丢弃）
+|TRUE（行被保留）
+|===
+
+两者对"不确定"的处理方向相反：`NOT` 丢弃，LNNVL 保留。
+严格而言，`NOT` 在三值逻辑下的行为是正确的；LNNVL 做的是把
+"未知视为不满足原条件"这一假设显式化，业务上通常这才是所需的结果。
+
+== 相关等价写法
+
+`LNNVL(cond)` 等价于 SQL 标准谓词 `cond IS NOT TRUE`。在不要求 Oracle
+兼容写法的场合可直接使用后者，两者的执行计划完全相同。
+
+对于 `NOT IN` 遇 NULL 的场景，PostgreSQL 的惯用解法是 `NOT EXISTS`：
+
+[source,sql]
+----
+SELECT count(*) FROM lnnvl_test t
+ WHERE NOT EXISTS (SELECT 1 FROM lnnvl_bl b WHERE b.d = t.id);
+----
+
+该写法与 `LNNVL(id IN (...))` 结果相同且更可移植；
+LNNVL 的优势在于改写成本 —— 它是就地包一层，
+而 `NOT EXISTS` 需要把子查询重构成相关子查询。
diff --git a/EN/modules/ROOT/nav.adoc b/EN/modules/ROOT/nav.adoc
index e4221c78..e117747f 100644
--- a/EN/modules/ROOT/nav.adoc
+++ b/EN/modules/ROOT/nav.adoc
@@ -31,7 +31,8 @@
 ** xref:master/oracle_compatibility/compat_create_index_online.adoc[22、ONLINE Parameter for CREATE INDEX]
 ** xref:master/oracle_compatibility/compat_stragg.adoc[23、STRAGG function]
 ** xref:master/oracle_compatibility/compat_alter_index_unusable_en.adoc[24、Alter Index Unusable]
-** xref:master/oracle_compatibility/compat_dbtimezone_en.adoc[24、dbtimezone]
+** xref:master/oracle_compatibility/compat_dbtimezone_en.adoc[25、dbtimezone]
+** xref:master/oracle_compatibility/compat_lnnvl.adoc[26、LNNVL Function]
 * Containerization and Cloud Service
 ** Containerization
 *** xref:master/containerization/k8s_deployment.adoc[K8S deployment]
@@ -116,6 +117,7 @@
 *** xref:master/oracle_builtin_functions/rawtohex.adoc[rawtohex]
 *** xref:master/oracle_builtin_functions/stragg.adoc[stragg]
 *** xref:master/oracle_builtin_functions/dbtimezone_impl_en.adoc[dbtimezone]
+*** xref:master/oracle_builtin_functions/lnnvl.adoc[lnnvl]
 ** xref:master/gb18030.adoc[GB18030 Character Set]
 * Reference
 ** xref:master/tools_reference.adoc[Tool Reference]
diff --git a/EN/modules/ROOT/pages/master/oracle_builtin_functions/lnnvl.adoc b/EN/modules/ROOT/pages/master/oracle_builtin_functions/lnnvl.adoc
new file mode 100644
index 00000000..a7fb3bd3
--- /dev/null
+++ b/EN/modules/ROOT/pages/master/oracle_builtin_functions/lnnvl.adoc
@@ -0,0 +1,145 @@
+:sectnums:
+:sectnumlevels: 5
+
+:imagesdir: ./_images
+
+= Implementation of the LNNVL Function
+
+== Purpose
+
+IvorySQL adds the `sys.lnnvl(boolean)` function in the `contrib/ivorysql_ora`
+extension, reproducing the behaviour of the Oracle function of the same name:
+it returns TRUE when the condition evaluates to FALSE or UNKNOWN, and FALSE
+when the condition evaluates to TRUE.
+
+== Implementation Notes
+
+=== Semantically Equivalent to IS NOT TRUE
+
+The truth table of LNNVL is cell-for-cell that of the SQL standard
+`IS NOT TRUE` predicate:
+
+[cols="1,1,1"]
+|===
+|Condition evaluates to |`LNNVL(cond)` |`cond IS NOT TRUE`
+
+|TRUE
+|FALSE
+|FALSE
+
+|FALSE
+|TRUE
+|TRUE
+
+|UNKNOWN
+|TRUE
+|TRUE
+|===
+
+No new evaluation logic is therefore required; the function body is just that
+predicate. In PostgreSQL, `IS NOT TRUE` is evaluated by the
+`EEOP_BOOLTEST_IS_NOT_TRUE` case in
+`src/backend/executor/execExprInterp.c`, which returns true and clears the
+result null flag when the argument is NULL. LNNVL consequently never returns
+NULL.
+
+=== SQL Definition
+
+The function is defined in
+`contrib/ivorysql_ora/src/builtin_functions/builtin_functions--1.0.sql`.
+
+[source,sql]
+----
+CREATE FUNCTION sys.lnnvl(pg_catalog.bool)
+RETURNS pg_catalog.bool
+AS $$SELECT $1 IS NOT TRUE$$
+LANGUAGE sql
+CALLED ON NULL INPUT
+PARALLEL SAFE
+IMMUTABLE;
+----
+
+Rationale for each property:
+
+[cols="1,1,3"]
+|===
+|Property |Value |Rationale
+
+|Schema
+|`sys`
+|Consistent with the other Oracle compatibility functions. `sys` enters the
+implicit `search_path` only in Oracle compatibility mode.
+
+|Argument type
+|`pg_catalog.bool`
+|Schema-qualified so that type name resolution is unaffected when `sys` is
+first in the `search_path` in Oracle mode.
+
+|Language
+|`sql`
+|Can be folded by `inline_function()`, see below. A C function would not be
+inlined.
+
+|NULL handling
+|`CALLED ON NULL INPUT`
+|Mandatory, see below.
+
+|Volatility
+|`IMMUTABLE`
+|Pure logic, same input always yields the same output; also a prerequisite for
+use in expression indexes.
+
+|Parallelism
+|`PARALLEL SAFE`
+|No side effects. Without this clause the default is `PARALLEL UNSAFE`, which
+disables parallel plans for any query using the function.
+|===
+
+=== CALLED ON NULL INPUT Is Mandatory
+
+`CALLED ON NULL INPUT` is the SQL default; it is spelled out here to keep it
+from being changed by mistake.
+
+Declared `STRICT`, the body would not run at all for a NULL argument and the
+result would be NULL rather than true, which removes the only reason the
+function exists, and it would do so silently. The risk comes from the pull
+towards stylistic consistency: most neighbouring functions in
+`builtin_functions--1.0.sql` are declared `STRICT`, so tidying this one to
+match its neighbours introduces the bug.
+
+`STRICT` also defeats inlining. Declaring a function strict promises that NULL
+in yields NULL out, while `IS NOT TRUE` is not itself a strict predicate, so
+the planner cannot expand it while preserving semantics and has to keep the
+function call:
+
+[source,text]
+----
+-- CALLED ON NULL INPUT
+Filter: (t.v IS NOT TRUE)
+
+-- STRICT
+Filter: f_strict(t.v)
+----
+
+Writing `STRICT` here therefore costs twice: the semantics are wrong and
+silently so, and performance degrades to a per-row function call.
+
+=== Function Inlining
+
+The body is a simple, inlinable SQL expression, so `inline_function()` folds
+it into the caller:
+
+[source,sql]
+----
+EXPLAIN (VERBOSE, COSTS OFF) SELECT id FROM t WHERE LNNVL(v >= 0.2);
+----
+
+[source,text]
+----
+ Seq Scan on public.t
+   Output: id
+   Filter: ((t.v >= 0.2) IS NOT TRUE)
+----
+
+No function call remains in the plan, which is identical to the plan for
+writing `IS NOT TRUE` by hand, so there is no additional runtime cost.
diff --git a/EN/modules/ROOT/pages/master/oracle_compatibility/compat_lnnvl.adoc b/EN/modules/ROOT/pages/master/oracle_compatibility/compat_lnnvl.adoc
new file mode 100644
index 00000000..e762a337
--- /dev/null
+++ b/EN/modules/ROOT/pages/master/oracle_compatibility/compat_lnnvl.adoc
@@ -0,0 +1,267 @@
+:sectnums:
+:sectnumlevels: 5
+
+:imagesdir: ./_images
+
+= LNNVL Function
+
+== Purpose
+
+This document describes the `sys.lnnvl` function in IvorySQL, which negates a
+condition in an Oracle compatible way and still returns TRUE when the condition
+evaluates to UNKNOWN.
+
+== Functional Description
+
+* `sys.lnnvl(boolean)` takes a condition and returns TRUE when it evaluates to
+  FALSE or UNKNOWN, and FALSE when it evaluates to TRUE.
+* The function **never returns NULL**. The result is always TRUE or FALSE, so it
+  can be used directly as a WHERE condition without introducing a new UNKNOWN.
+* Its main use is to eliminate the row loss caused by three-valued logic: with a
+  plain `NOT`, rows whose condition is UNKNOWN are dropped both by the original
+  condition and by its negation, whereas a condition and its LNNVL partition the
+  table strictly, so the two row counts always add up to the total.
+
+Truth table:
+
+[cols="1,1"]
+|===
+|Condition evaluates to |Return value
+
+|TRUE
+|FALSE
+
+|FALSE
+|TRUE
+
+|UNKNOWN (condition involves NULL)
+|TRUE
+|===
+
+== Syntax
+
+[source,sql]
+----
+sys.lnnvl(condition)
+----
+
+[cols="1,3"]
+|===
+|Parameter |Description
+
+|`condition`
+|Any boolean expression. Non-boolean types are not accepted and there is no
+implicit cast from integer.
+|===
+
+Return type: `boolean`
+
+== Test Cases
+
+=== Test Environment Setup
+
+[source,sql]
+----
+CREATE TABLE lnnvl_test (a INT, b INT);
+INSERT INTO lnnvl_test VALUES (2, NULL);
+----
+
+=== Truth Table Verification
+
+[source,sql]
+----
+-- a = 2, b is NULL
+SELECT LNNVL(a = 1) FROM lnnvl_test;        -- expected: t (condition is FALSE)
+SELECT LNNVL(a = 2) FROM lnnvl_test;        -- expected: f (condition is TRUE)
+SELECT LNNVL(a IS NULL) FROM lnnvl_test;    -- expected: t (condition is FALSE)
+SELECT LNNVL(b = 1) FROM lnnvl_test;        -- expected: t (condition is UNKNOWN)
+SELECT LNNVL(b IS NULL) FROM lnnvl_test;    -- expected: f (condition is TRUE)
+SELECT LNNVL(a = b) FROM lnnvl_test;        -- expected: t (condition is UNKNOWN)
+----
+
+=== NULL Argument
+
+[source,sql]
+----
+-- A NULL argument must return t; this is the core behaviour of LNNVL
+SELECT LNNVL(NULL);                         -- expected: t
+SELECT LNNVL(NULL::boolean);                -- expected: t
+----
+
+=== Partition Property
+
+[source,sql]
+----
+DROP TABLE lnnvl_test;
+CREATE TABLE lnnvl_test (id INT, v NUMERIC);
+INSERT INTO lnnvl_test VALUES (1,0.30),(2,0.10),(3,NULL),(4,0.25),(5,NULL);
+
+SELECT count(*) FROM lnnvl_test WHERE v >= 0.2;          -- expected: 2
+SELECT count(*) FROM lnnvl_test WHERE LNNVL(v >= 0.2);   -- expected: 3
+SELECT count(*) FROM lnnvl_test;                         -- expected: 5
+
+-- 2 + 3 = 5: the condition and its LNNVL cover the whole table, no row is lost
+-- With NOT, the two counts add up to less than the total
+SELECT count(*) FROM lnnvl_test WHERE NOT (v >= 0.2);    -- expected: 2, total only 4
+----
+
+=== NOT IN over a Subquery Containing NULL
+
+[source,sql]
+----
+CREATE TABLE lnnvl_bl (d INT);
+INSERT INTO lnnvl_bl VALUES (1), (NULL);
+
+-- With a NULL in the list, NOT IN matches nothing
+SELECT count(*) FROM lnnvl_test WHERE id NOT IN (SELECT d FROM lnnvl_bl);
+-- expected: 0
+
+-- Rewritten with LNNVL(... IN ...) it gives the intuitive result
+SELECT count(*) FROM lnnvl_test WHERE LNNVL(id IN (SELECT d FROM lnnvl_bl));
+-- expected: 4
+----
+
+`id NOT IN (1, NULL)` expands to `id <> 1 AND id <> NULL`, where
+`id <> NULL` is always UNKNOWN, so the whole condition is never TRUE and every
+row is dropped. `LNNVL(id IN (...))` treats UNKNOWN as "not true" and keeps
+those rows.
+
+=== Argument Type Checking
+
+[source,sql]
+----
+-- The argument must be boolean; there is no implicit cast from integer
+SELECT LNNVL(1);
+-- expected error: function lnnvl(pg_catalog.int4) does not exist
+----
+
+=== Test Environment Cleanup
+
+[source,sql]
+----
+DROP TABLE lnnvl_bl;
+DROP TABLE lnnvl_test;
+----
+
+== Behavioral Differences from Oracle
+
+Oracle's grammar accepts only a single simple condition. IvorySQL implements
+LNNVL as an ordinary function, and by the time overload resolution runs its
+argument is already a boolean expression: the `AND`, `OR`, `NOT` or `BETWEEN`
+that produced it is no longer visible to the function. The restrictions
+therefore cannot be reproduced, and **the accepted forms are a superset of
+Oracle's**.
+
+The direction is safe: any LNNVL usage that runs on Oracle also runs on
+IvorySQL, but not the reverse -- a compound form written on IvorySQL will raise
+an error when moved back to Oracle.
+
+[cols="2,1,1"]
+|===
+|Argument form |Oracle |IvorySQL
+
+|`LNNVL(1 = 1 AND 2 = 2)`
+|rejected
+|accepted, returns f
+
+|`LNNVL(1 = 1 OR 2 = 2)`
+|rejected
+|accepted, returns f
+
+|`LNNVL(1 BETWEEN 0 AND 5)`
+|rejected
+|accepted, returns f
+
+|`LNNVL(1 NOT BETWEEN 0 AND 5)`
+|rejected
+|accepted, returns t
+
+|`LNNVL(NOT (1 = 1))`
+|rejected (ORA-00936)
+|accepted, returns t
+
+|`LNNVL(NOT EXISTS (SELECT ...))`
+|rejected (ORA-00936)
+|accepted, returns t
+
+|`LNNVL(1 IN (1,2))`
+|rejected (ORA-13207)
+|accepted, returns f
+
+|`LNNVL(1 NOT IN (1,2))`
+|rejected (ORA-13207)
+|accepted, returns t
+|===
+
+Other differences:
+
+[cols="1,2,2"]
+|===
+|Aspect |Oracle |IvorySQL
+
+|Error codes and text
+|`ORA-` numbers
+|PostgreSQL SQLSTATE values and wording
+
+|`LNNVL(1)`
+|Handled by its BOOLEAN type conversion rules
+|Reports that no such function exists; no implicit cast
+|===
+
+To express a compound condition, follow the Oracle practice of splitting it
+into several LNNVL calls combined with `AND` or `OR`:
+
+[source,sql]
+----
+SELECT LNNVL(1 = 1) OR LNNVL(2 = 3);    -- expected: f
+SELECT LNNVL(1 = 1) AND LNNVL(2 = 3);   -- expected: f
+SELECT NOT LNNVL(1 = 1);                -- expected: t
+----
+
+Note that De Morgan's laws apply when splitting: `LNNVL(A AND B)` corresponds to
+`LNNVL(A) OR LNNVL(B)`; using `AND` changes the result.
+
+== Comparison with NOT
+
+[cols="1,2,2"]
+|===
+|Condition evaluates to |`NOT cond` |`LNNVL(cond)`
+
+|TRUE
+|FALSE
+|FALSE
+
+|FALSE
+|TRUE
+|TRUE
+
+|UNKNOWN
+|UNKNOWN (row dropped)
+|TRUE (row kept)
+|===
+
+The two treat "unknown" in opposite directions: `NOT` discards it, LNNVL keeps
+it. Strictly speaking the behaviour of `NOT` is correct under three-valued
+logic; what LNNVL does is make the assumption "unknown means the original
+condition is not satisfied" explicit, which is usually the intended result in
+practice.
+
+== Equivalent Formulations
+
+`LNNVL(cond)` is equivalent to the SQL standard predicate
+`cond IS NOT TRUE`. Where Oracle compatible syntax is not required, the latter
+can be used directly; the execution plans are identical.
+
+For the NOT IN with NULL case, the idiomatic PostgreSQL solution is
+`NOT EXISTS`:
+
+[source,sql]
+----
+SELECT count(*) FROM lnnvl_test t
+ WHERE NOT EXISTS (SELECT 1 FROM lnnvl_bl b WHERE b.d = t.id);
+----
+
+That form gives the same result as `LNNVL(id IN (...))` and is more portable.
+The advantage of LNNVL is the cost of rewriting: it wraps an existing condition
+in place, whereas `NOT EXISTS` requires restructuring the subquery into a
+correlated one.