MariaDB · DaveGosselin-MariaDB · Oct 29, 2025
diff --git a/mysql-test/main/join.result b/mysql-test/main/join.result
@@ -3657,3 +3657,27 @@ DROP TABLE t1,t2,t3;
 #
 # End of 11.0 tests
 #
+#
+# MDEV-37932: FULL OUTER JOIN: Make the parser support FULL OUTER JOIN
+#             syntax
+#
+create table t1 (a int);
+insert into t1 (a) values (1),(2),(3);
+create table t2 (a int);
+insert into t2 (a) values (1),(2),(3);
+select * from t1 full join t2 on t1.a = t2.a;
+ERROR 42000: This version of MariaDB doesn't yet support 'full join'
+select * from t1 full outer join t2 on t1.a = t2.a;
+ERROR 42000: This version of MariaDB doesn't yet support 'full join'
+select * from t1 natural full outer join t2;
+ERROR 42000: This version of MariaDB doesn't yet support 'full join'
+select * from t1 natural full join t2;
+ERROR 42000: This version of MariaDB doesn't yet support 'full join'
+create view v1 as select * from t1 full outer join t2 on t1.a = t2.a;
+ERROR 42000: This version of MariaDB doesn't yet support 'full join'
+select * from (select t1.a from t1 full outer join t2 on t1.a = t2.a union select * from t1) dt;
+ERROR 42000: This version of MariaDB doesn't yet support 'full join'
+with cte as (select t1.a from t1 natural full join t2) select * from cte;
+ERROR 42000: This version of MariaDB doesn't yet support 'full join'
+drop table t1, t2;
+# End of 12.3 tests
diff --git a/mysql-test/main/join.test b/mysql-test/main/join.test
@@ -2046,3 +2046,30 @@ DROP TABLE t1,t2,t3;
 --echo #
 --echo # End of 11.0 tests
 --echo #
+
+--echo #
+--echo # MDEV-37932: FULL OUTER JOIN: Make the parser support FULL OUTER JOIN
+--echo #             syntax
+--echo #
+create table t1 (a int);
+insert into t1 (a) values (1),(2),(3);
+create table t2 (a int);
+insert into t2 (a) values (1),(2),(3);
+# This test only verifies syntax acceptance.
+--error ER_NOT_SUPPORTED_YET
+select * from t1 full join t2 on t1.a = t2.a;
+--error ER_NOT_SUPPORTED_YET
+select * from t1 full outer join t2 on t1.a = t2.a;
+--error ER_NOT_SUPPORTED_YET
+select * from t1 natural full outer join t2;
+--error ER_NOT_SUPPORTED_YET
+select * from t1 natural full join t2;
+--error ER_NOT_SUPPORTED_YET
+create view v1 as select * from t1 full outer join t2 on t1.a = t2.a;
+--error ER_NOT_SUPPORTED_YET
+select * from (select t1.a from t1 full outer join t2 on t1.a = t2.a union select * from t1) dt;
+--error ER_NOT_SUPPORTED_YET
+with cte as (select t1.a from t1 natural full join t2) select * from cte;
+drop table t1, t2;
+
+--echo # End of 12.3 tests
diff --git a/sql/sql_lex.cc b/sql/sql_lex.cc
@@ -1343,6 +1343,7 @@ void LEX::start(THD *thd_arg)
 
   memset(&trg_chistics, 0, sizeof(trg_chistics));
   selects_for_hint_resolution.empty();
+  has_full_outer_join= false;
   DBUG_VOID_RETURN;
 }
 

diff --git a/sql/sql_lex.h b/sql/sql_lex.h
@@ -3593,6 +3593,9 @@ struct LEX: public Query_tables_list
   vers_select_conds_t vers_conditions;
   vers_select_conds_t period_conditions;
 
+  /* False by default, this will be true if the query has a full join. */
+  bool has_full_outer_join;
+
   inline void free_set_stmt_mem_root()
   {
     DBUG_ASSERT(!is_arena_for_set_stmt());

diff --git a/sql/sql_parse.cc b/sql/sql_parse.cc
@@ -10305,6 +10305,11 @@ bool parse_sql(THD *thd, Parser_state *parser_state,
   bool mysql_parse_status= thd->variables.sql_mode & MODE_ORACLE
                            ? ORAparse(thd) : MYSQLparse(thd);
 
+  /* While we accept full join syntax, such joins are not yet supported. */
+  mysql_parse_status|= thd->lex->has_full_outer_join;
+  if (thd->lex->has_full_outer_join)
+    my_error(ER_NOT_SUPPORTED_YET, MYF(0), "full join");
+
   if (mysql_parse_status)
     /*
       Restore the original LEX if it was replaced when parsing

diff --git a/sql/sql_yacc.yy b/sql/sql_yacc.yy
@@ -1183,8 +1183,8 @@ bool my_yyoverflow(short **a, YYSTYPE **b, size_t *yystacksize);
 %token  <kwd>   ST_COLLECT_SYM
 /* A dummy token to force the priority of table_ref production in a join. */
 %left   CONDITIONLESS_JOIN
-%left   JOIN_SYM INNER_SYM STRAIGHT_JOIN CROSS LEFT RIGHT ON_SYM USING
- 
+%left   JOIN_SYM INNER_SYM STRAIGHT_JOIN CROSS LEFT RIGHT ON_SYM USING FULL
+
 %left   SET_VAR
 %left   OR_SYM OR2_SYM
 %left   XOR
@@ -12365,8 +12365,66 @@ join_table:
             if (unlikely(!($$= lex->current_select->convert_right_join())))
               MYSQL_YYABORT;
           }
-        ;
 
+          /* FULL OUTER JOIN variants */
+        | table_ref FULL opt_outer JOIN_SYM table_ref
+          ON
+          {
+            MYSQL_YYABORT_UNLESS($1 && $5);
+
+            Select->add_joined_table($1);
+            $1->outer_join|= (JOIN_TYPE_LEFT |
+                              JOIN_TYPE_FULL);
+
+            Select->add_joined_table($5);
+            $5->outer_join|= (JOIN_TYPE_RIGHT |
+                              JOIN_TYPE_FULL);
+
+            /* Change the current name resolution context to a local context. */
+            if (unlikely(push_new_name_resolution_context(thd, $1, $5)))
+              MYSQL_YYABORT;
+            Select->parsing_place= IN_ON;
+          }
+          expr
+          {
+            add_join_on(thd, $1, $8);
+            $1->on_context= Lex->pop_context();
+            Select->parsing_place= NO_MATTER;
+            $$= $1;
+            Lex->has_full_outer_join= true;
+          }
+        | table_ref FULL opt_outer JOIN_SYM table_factor
+          {
+            MYSQL_YYABORT_UNLESS($1 && $5);
+            Select->add_joined_table($1);
+            $1->outer_join|= (JOIN_TYPE_LEFT |
+                              JOIN_TYPE_FULL);
+
+            Select->add_joined_table($5);
+            $5->outer_join|= (JOIN_TYPE_RIGHT |
+                              JOIN_TYPE_FULL);
+          }
+          USING '(' using_list ')'
+          {
+            add_join_natural($1,$5,$9,Select);
+            Lex->has_full_outer_join= true;
+          }
+        | table_ref NATURAL FULL opt_outer JOIN_SYM table_factor
+          {
+            MYSQL_YYABORT_UNLESS($1 && $6);
+
+            Select->add_joined_table($1);
+            $1->outer_join|= (JOIN_TYPE_LEFT |
+                              JOIN_TYPE_FULL);
+
+            Select->add_joined_table($6);
+            $6->outer_join|= (JOIN_TYPE_RIGHT |
+                              JOIN_TYPE_FULL);
+
+            add_join_natural($6,$1,NULL,Select);
+            Lex->has_full_outer_join= true;
+          }
+        ;
 
 inner_join: /* $$ set if using STRAIGHT_JOIN, false otherwise */
           JOIN_SYM           { $$ = 0; }
@@ -16691,7 +16749,6 @@ keyword_func_sp_var_and_label:
         | FILE_SYM
         | FIRST_SYM
         | FOUND_SYM
-        | FULL
         | GENERAL
         | GENERATED_SYM
         | GRANTS
@@ -17021,6 +17078,7 @@ reserved_keyword_udt_not_param_type:
         | FIRST_VALUE_SYM
         | FOREIGN
         | FROM
+        | FULL
         | FULLTEXT_SYM
         | GOTO_ORACLE_SYM
         | GRANT
@@ -17748,6 +17806,7 @@ set_expr_or_default:
 set_expr_misc:
           ON     { $$= new (thd->mem_root) Item_string_sys(thd, "ON",  2); }
         | ALL    { $$= new (thd->mem_root) Item_string_sys(thd, "ALL", 3); }
+        | FULL   { $$= new (thd->mem_root) Item_string_sys(thd, "FULL", 4); }
         | BINARY { $$= new (thd->mem_root) Item_string_sys(thd, "binary", 6); }
         ;
 

diff --git a/sql/table.h b/sql/table.h
@@ -2214,7 +2214,8 @@ class IS_table_read_plan;
 
 #define JOIN_TYPE_LEFT	1U
 #define JOIN_TYPE_RIGHT	2U
-#define JOIN_TYPE_OUTER 4U	/* Marker that this is an outer join */
+#define JOIN_TYPE_FULL	4U
+#define JOIN_TYPE_OUTER 8U	/* Marker that this is an outer join */
 
 /* view WITH CHECK OPTION parameter options */
 #define VIEW_CHECK_NONE       0