diff --git a/src/common/backend/nodes/copyfuncs.cpp b/src/common/backend/nodes/copyfuncs.cpp
index 1778be377..ed70acb80 100644
--- a/src/common/backend/nodes/copyfuncs.cpp
+++ b/src/common/backend/nodes/copyfuncs.cpp
@@ -2362,6 +2362,11 @@ static IntoClause* _copyIntoClause(const IntoClause* from)
     COPY_STRING_FIELD(filename);
     COPY_SCALAR_FIELD(is_outfile);
 
+    if (t_thrd.proc->workingVersionNum >= CREATE_TABLE_AS_VERSION_NUM) {
+        COPY_NODE_FIELD(tableElts);
+        COPY_NODE_FIELD(autoIncStart);
+        COPY_SCALAR_FIELD(onduplicate);
+    }
     return newnode;
 }
 
diff --git a/src/common/backend/nodes/equalfuncs.cpp b/src/common/backend/nodes/equalfuncs.cpp
index 9b08dede9..34127f427 100644
--- a/src/common/backend/nodes/equalfuncs.cpp
+++ b/src/common/backend/nodes/equalfuncs.cpp
@@ -150,6 +150,11 @@ static bool _equalIntoClause(const IntoClause* a, const IntoClause* b)
     COMPARE_STRING_FIELD(filename);
     COMPARE_SCALAR_FIELD(is_outfile);
 
+    if (t_thrd.proc->workingVersionNum >= CREATE_TABLE_AS_VERSION_NUM) {
+        COMPARE_NODE_FIELD(tableElts);
+        COMPARE_NODE_FIELD(autoIncStart);
+        COMPARE_SCALAR_FIELD(onduplicate);
+    }
     return true;
 }
 
diff --git a/src/common/backend/nodes/outfuncs.cpp b/src/common/backend/nodes/outfuncs.cpp
index 381a6434e..cecfddd5d 100755
--- a/src/common/backend/nodes/outfuncs.cpp
+++ b/src/common/backend/nodes/outfuncs.cpp
@@ -2180,6 +2180,11 @@ static void _outIntoClause(StringInfo str, IntoClause* node)
         WRITE_STRING_FIELD(filename);
         WRITE_BOOL_FIELD(is_outfile);
     }
+    if (t_thrd.proc->workingVersionNum >= CREATE_TABLE_AS_VERSION_NUM) {
+        WRITE_NODE_FIELD(tableElts);
+        WRITE_NODE_FIELD(autoIncStart);
+        WRITE_ENUM_FIELD(onduplicate, OnDuplicateAction);
+    }
 }
 
 static void _outVar(StringInfo str, Var* node)
diff --git a/src/common/backend/nodes/readfuncs.cpp b/src/common/backend/nodes/readfuncs.cpp
index be010670b..f3147fef7 100755
--- a/src/common/backend/nodes/readfuncs.cpp
+++ b/src/common/backend/nodes/readfuncs.cpp
@@ -1982,6 +1982,15 @@ static IntoClause* _readIntoClause(void)
         READ_BOOL_FIELD(is_outfile);
     }
 
+    IF_EXIST(tableElts) {
+        READ_NODE_FIELD(tableElts);
+    }
+    IF_EXIST(autoIncStart) {
+        READ_NODE_FIELD(autoIncStart);
+    }
+    IF_EXIST(onduplicate) {
+        READ_ENUM_FIELD(onduplicate, OnDuplicateAction);
+    }
     READ_DONE();
 }
 
diff --git a/src/common/backend/parser/analyze.cpp b/src/common/backend/parser/analyze.cpp
index eadea9cbc..a1ed3c880 100644
--- a/src/common/backend/parser/analyze.cpp
+++ b/src/common/backend/parser/analyze.cpp
@@ -2283,7 +2283,8 @@ static void checkUpsertTargetlist(Relation targetTable, List* updateTlist)
             }
         }
 
-        if (bms_overlap(index_attrs, target_attrs)) {
+        /* Allow in B_FORMAT */
+        if (bms_overlap(index_attrs, target_attrs) && u_sess->attr.attr_sql.sql_compatibility != B_FORMAT) {
             ereport(ERROR, ((errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                          errmsg("INSERT ON DUPLICATE KEY UPDATE don't allow update on primary key or unique key."))));
         }
@@ -4501,6 +4502,38 @@ static Query* transformCreateTableAsStmt(ParseState* pstate, CreateTableAsStmt*
     /* transform contained query */
     stmt->query = (Node*)transformStmt(pstate, stmt->query);
 
+    if (u_sess->attr.attr_sql.sql_compatibility == B_FORMAT) {
+        /* CREATE TABLE AS SELECT is not allowed with Foreign Key and Tablelike Clause*/
+        foreach (lc, stmt->into->tableElts) {
+            Node* node = (Node*)lfirst(lc);
+            if (IsA(node, ColumnDef)) {
+                ColumnDef* col = (ColumnDef*) node;
+                ListCell* cell = NULL;
+                foreach(cell, col->constraints){
+                    if (IsA(lfirst(cell), Constraint)) {
+                        Constraint* constraint = (Constraint*) lfirst(cell);
+                        if (constraint->contype == CONSTR_FOREIGN) {
+                            ereport(ERROR,
+                                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+                                errmsg("CREATE TABLE AS SELECT is not allowed with Foreign Key")));
+                        }
+                    }
+                }
+            } else if (IsA(node, Constraint)) {
+                Constraint* constraint = (Constraint*) node;
+                if (constraint->contype == CONSTR_FOREIGN) {
+                    ereport(ERROR,
+                        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+                        errmsg("CREATE TABLE AS SELECT is not allowed with Foreign Key")));
+                }
+            } else if (IsA(node, TableLikeClause)) {
+                ereport(ERROR,
+                        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+                        errmsg("CREATE TABLE AS SELECT is not allowed with Tablelike Clause")));
+            }
+        }
+    }
+
     /* if result type of new relation is unknown-type, then resolve as type TEXT */
     foreach (lc, ((Query*)stmt->query)->targetList) {
         TargetEntry* tle = (TargetEntry*)lfirst(lc);
diff --git a/src/common/backend/parser/gram.y b/src/common/backend/parser/gram.y
index 4e7516298..edc507482 100644
--- a/src/common/backend/parser/gram.y
+++ b/src/common/backend/parser/gram.y
@@ -336,6 +336,7 @@ static void setDelimiterName(core_yyscan_t yyscanner, char*input, VariableSetStm
 	EncryptionType algtype;
 	LockClauseStrength lockstrength;
 	CharsetCollateOptions *charsetcollateopt;
+	OnDuplicateAction onduplicate;
 }
 
 %type <node>	stmt schema_stmt
@@ -549,6 +550,7 @@ static void setDelimiterName(core_yyscan_t yyscanner, char*input, VariableSetStm
 %type <boolean>  opt_trusted opt_restart_seqs opt_purge invoker_rights
 %type <ival>	 OptTemp OptKind
 %type <oncommit> OnCommitOption
+%type <onduplicate>	OptDuplicate
 %type <lockstrength> for_locking_strength
 %type <node>	for_locking_item
 %type <list>	for_locking_clause opt_for_locking_clause for_locking_items
@@ -873,7 +875,7 @@ static void setDelimiterName(core_yyscan_t yyscanner, char*input, VariableSetStm
 
 	HANDLER HAVING HDFSDIRECTORY HEADER_P HOLD HOUR_P
 
-	IDENTIFIED IDENTITY_P IF_P IGNORE_EXTRA_DATA ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IN_P INCLUDE
+	IDENTIFIED IDENTITY_P IF_P IGNORE IGNORE_EXTRA_DATA ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IN_P INCLUDE
 	INCLUDING INCREMENT INCREMENTAL INDEX INDEXES INFILE INHERIT INHERITS INITIAL_P INITIALLY INITRANS INLINE_P
 
 	INNER_P INOUT INPUT_P INSENSITIVE INSERT INSTEAD INT_P INTEGER INTERNAL
@@ -9150,6 +9152,12 @@ CreateAsStmt:
 				}
 		;
 
+OptDuplicate:
+			/* empty */	{ $$ = DUPLICATE_ERROR; }
+			| IGNORE	{ $$ = DUPLICATE_IGNORE; }
+			| REPLACE	{ $$ = DUPLICATE_REPLACE; }
+		;
+
 create_as_target:
 			qualified_name opt_column_list OptWith OnCommitOption OptCompress OptTableSpace
 /* PGXC_BEGIN */
@@ -9170,6 +9178,36 @@ create_as_target:
 					$$->relkind = INTO_CLAUSE_RELKIND_DEFAULT;
 /* PGXC_END */
 				}
+			| qualified_name '(' OptTableElementList ')' OptInherit OptAutoIncrement optCharsetCollate OptWith OnCommitOption OptCompress OptPartitionElement
+/* PGXC_BEGIN */
+			OptDistributeBy OptSubCluster
+/* PGXC_END */
+			OptDuplicate
+				{
+					if (u_sess->attr.attr_sql.sql_compatibility != B_FORMAT) {
+						ereport(errstate, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+								errmsg("define column_definition is supported only in B-format database")));
+					}
+					$$ = makeNode(IntoClause);
+					$$->rel = $1;
+					$$->tableElts = $3;
+					if ($$->tableElts == NIL) {
+						ereport(ERROR, (errcode(ERRCODE_SYNTAX_ERROR),
+						errmsg("syntax error at or near \"%s\"", ")"), parser_errposition(@4)));
+					}
+					$$->autoIncStart = $6;
+					$$->options = $8;
+					$$->onCommit = $9;
+					$$->row_compress = $10;
+					$$->tableSpaceName = $11;
+					$$->skipData = false;           /* might get changed later */
+/* PGXC_BEGIN */
+					$$->distributeby = $12;
+					$$->subcluster = $13;
+					$$->relkind = INTO_CLAUSE_RELKIND_DEFAULT;
+/* PGXC_END */
+					$$->onduplicate = $14;
+				}
 		;
 
 opt_with_data:
diff --git a/src/common/backend/utils/init/globals.cpp b/src/common/backend/utils/init/globals.cpp
index e13c8c9ee..369095557 100644
--- a/src/common/backend/utils/init/globals.cpp
+++ b/src/common/backend/utils/init/globals.cpp
@@ -179,6 +179,7 @@ const uint32 CREATE_INDEX_IF_NOT_EXISTS_VERSION_NUM = 92843;
 const uint32 EVENT_VERSION_NUM = 92844;
 
 const uint32 SLOW_SQL_VERSION_NUM = 92844;
+const uint32 CREATE_TABLE_AS_VERSION_NUM = 92845;
 #ifdef PGXC
 bool useLocalXid = false;
 #endif
diff --git a/src/common/interfaces/libpq/frontend_parser/gram.y b/src/common/interfaces/libpq/frontend_parser/gram.y
index a444f9fa2..aa4f447e5 100755
--- a/src/common/interfaces/libpq/frontend_parser/gram.y
+++ b/src/common/interfaces/libpq/frontend_parser/gram.y
@@ -545,7 +545,7 @@ extern THR_LOCAL bool stmt_contains_operator_plus;
 
 	HANDLER HAVING HDFSDIRECTORY HEADER_P HOLD HOUR_P
 
-	IDENTIFIED IDENTITY_P IF_P IGNORE_EXTRA_DATA ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IN_P
+	IDENTIFIED IDENTITY_P IF_P IGNORE IGNORE_EXTRA_DATA ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IN_P
 	INCLUDE INCLUDING INCREMENT INCREMENTAL INDEX INDEXES INFILE INHERIT INHERITS INITIAL_P INITIALLY INITRANS INLINE_P
 	INNER_P INOUT INPUT_P INSENSITIVE INSERT INSTEAD INT_P INTEGER INTERNAL
 	INTERSECT INTERVAL INTO INVISIBLE INVOKER IP IS ISNULL ISOLATION
diff --git a/src/gausskernel/optimizer/rewrite/rewriteHandler.cpp b/src/gausskernel/optimizer/rewrite/rewriteHandler.cpp
index 795c7155a..6581e5e50 100644
--- a/src/gausskernel/optimizer/rewrite/rewriteHandler.cpp
+++ b/src/gausskernel/optimizer/rewrite/rewriteHandler.cpp
@@ -87,6 +87,7 @@ static void markQueryForLocking(Query* qry, Node* jtnode, LockClauseStrength str
 static List* matchLocks(CmdType event, RuleLock* rulelocks, int varno, Query* parsetree);
 static Query* fireRIRrules(Query* parsetree, List* activeRIRs, bool forUpdatePushedDown);
 static Bitmapset* adjust_view_column_set(Bitmapset* cols, List* targetlist);
+static bool findAttrByName(const char* attributeName, List* tableElts, int maxlen);
 
 #ifdef PGXC
 typedef struct pull_qual_vars_context {
@@ -4406,6 +4407,25 @@ char* GetCreateViewStmt(Query* parsetree, CreateTableAsStmt* stmt)
     return cquery->data;
 }
 
+static bool findAttrByName(const char* attributeName, List* tableElts, int maxlen)
+{
+    ListCell* lc = NULL;
+    int i = 0;
+    foreach (lc, tableElts) {
+        if (i >= maxlen) {
+            return false;
+        }
+        Node* node = (Node*)lfirst(lc);
+        if (IsA(node, ColumnDef)) {
+            ColumnDef* def = (ColumnDef*)node;
+            if (pg_strcasecmp(attributeName, def->colname) == 0)
+                return true;
+        }
+        ++i;
+    }
+    return false;
+}
+
 char* GetCreateTableStmt(Query* parsetree, CreateTableAsStmt* stmt)
 {
     /* Start building a CreateStmt for creating the target table */
@@ -4415,6 +4435,10 @@ char* GetCreateTableStmt(Query* parsetree, CreateTableAsStmt* stmt)
     IntoClause* into = stmt->into;
     List* tableElts = NIL;
 
+    if (u_sess->attr.attr_sql.sql_compatibility == B_FORMAT)
+        tableElts = stmt->into->tableElts;
+    int initlen = list_length(tableElts);
+
     /* Obtain the target list of new table */
     AssertEreport(IsA(stmt->query, Query), MOD_OPT, "");
     Query* cparsetree = (Query*)stmt->query;
@@ -4455,6 +4479,10 @@ char* GetCreateTableStmt(Query* parsetree, CreateTableAsStmt* stmt)
         if (tle->resjunk)
             continue;
 
+        if (u_sess->attr.attr_sql.sql_compatibility == B_FORMAT && findAttrByName(tle->resname, tableElts, initlen)) {
+            continue;
+        }
+
         coldef = makeNode(ColumnDef);
         tpname = makeNode(TypeName);
     
@@ -4528,6 +4556,9 @@ char* GetCreateTableStmt(Query* parsetree, CreateTableAsStmt* stmt)
     create_stmt->options = stmt->into->options;
     create_stmt->ivm = stmt->into->ivm;
     create_stmt->relkind = stmt->relkind == OBJECT_MATVIEW ? RELKIND_MATVIEW : RELKIND_RELATION;
+    if (u_sess->attr.attr_sql.sql_compatibility == B_FORMAT) {
+        create_stmt->autoIncStart = stmt->into->autoIncStart;
+    }
     /*
      * Check consistency of arguments
      */
@@ -4561,7 +4592,8 @@ char* GetCreateTableStmt(Query* parsetree, CreateTableAsStmt* stmt)
 
     StringInfo cquery = makeStringInfo();
 
-    deparse_query(parsetree, cquery, NIL, false, false);
+    if (u_sess->attr.attr_sql.sql_compatibility != B_FORMAT || initlen <= 0)
+        deparse_query(parsetree, cquery, NIL, false, false);
 
     return cquery->data;
 }
@@ -4599,7 +4631,7 @@ static void _copy_top_HintState(HintState *dest, HintState *src)
     dest->no_expand_hint = src->no_expand_hint;
 }
 
-char* GetInsertIntoStmt(CreateTableAsStmt* stmt)
+char* GetInsertIntoStmt(CreateTableAsStmt* stmt, bool hasNewColumn)
 {
     /* Get the SELECT query string */
     /*
@@ -4642,6 +4674,23 @@ char* GetInsertIntoStmt(CreateTableAsStmt* stmt)
     else
         appendStringInfo(cquery, " INTO %s", quote_identifier(relation->relname));
 
+    /* if has new column and have data to insert */
+    if (u_sess->attr.attr_sql.sql_compatibility == B_FORMAT && hasNewColumn && !stmt->into->skipData) {
+        appendStringInfoString(cquery, " (");
+        ListCell* lc = NULL;
+        const char* delimiter = "";
+        foreach (lc, select_query->targetList) {
+            TargetEntry* tle = (TargetEntry*)lfirst(lc);
+            /* ignore junk column*/
+            if (tle->resjunk)
+                continue;
+            appendStringInfoString(cquery, delimiter);
+            delimiter = ", ";
+            appendStringInfo(cquery, "%s", quote_identifier(tle->resname));
+        }
+        appendStringInfoString(cquery, ")");
+    }
+
     /*
      * If the original sql contains "WITH NO DATA", just create
      * the table without inserting any data.
@@ -4651,6 +4700,33 @@ char* GetInsertIntoStmt(CreateTableAsStmt* stmt)
     else
         appendStringInfo(cquery, " %s", selectstr);
 
+    /* If there is a new column, there may be a uniqueness conflict */
+    if (u_sess->attr.attr_sql.sql_compatibility == B_FORMAT && hasNewColumn && !stmt->into->skipData) {
+        switch (stmt->into->onduplicate) {
+            case DUPLICATE_ERROR:
+                break;
+            case DUPLICATE_IGNORE:
+                appendStringInfoString(cquery, " ON DUPLICATE KEY UPDATE NOTHING");
+                break;
+            case DUPLICATE_REPLACE: {
+                appendStringInfoString(cquery, " ON DUPLICATE KEY UPDATE ");
+                ListCell* lc = NULL;
+                const char* delimiter = "";
+                foreach (lc, select_query->targetList) {
+                    TargetEntry* tle = (TargetEntry*)lfirst(lc);
+                    /* ignore junk column*/
+                    if (tle->resjunk)
+                        continue;
+                    appendStringInfoString(cquery, delimiter);
+                    delimiter = ", ";
+                    appendStringInfo(cquery, "%s = VALUES(%s)", quote_identifier(tle->resname), quote_identifier(tle->resname));
+                }
+                break;
+            }
+            default:
+                break;
+        }
+    }
     return cquery->data;
 }
 
@@ -4886,7 +4962,10 @@ List* QueryRewriteCTAS(Query* parsetree)
 
     /* CREATE TABLE AS */
     Query* cparsetree = (Query*)copyObject(parsetree);
+    bool hasNewColumn = stmt->into->tableElts != NULL;
     char* create_sql = GetCreateTableStmt(cparsetree, stmt);
+    /* move stmt->into->tableElts to create_stmt->tableElts */
+    stmt->into->tableElts = NULL;
 
     if (stmt->relkind == OBJECT_MATVIEW) {
         zparsetree = (Query*)copyObject(cparsetree);
@@ -4938,7 +5017,7 @@ List* QueryRewriteCTAS(Query* parsetree)
         */
     parsetree->utilityStmt = NULL;
 
-    char* insert_into_sqlstr = GetInsertIntoStmt(stmt);
+    char* insert_into_sqlstr = GetInsertIntoStmt(stmt, hasNewColumn);
 
     raw_parsetree_list = pg_parse_query(insert_into_sqlstr);
 
diff --git a/src/include/miscadmin.h b/src/include/miscadmin.h
index 53d09e6d2..116c954d7 100644
--- a/src/include/miscadmin.h
+++ b/src/include/miscadmin.h
@@ -127,6 +127,7 @@ extern const uint32 INSERT_RIGHT_REF_VERSION_NUM;
 extern const uint32 CREATE_INDEX_IF_NOT_EXISTS_VERSION_NUM;
 extern const uint32 SLOW_SQL_VERSION_NUM;
 extern const uint32 INDEX_HINT_VERSION_NUM;
+extern const uint32 CREATE_TABLE_AS_VERSION_NUM;
 
 extern void register_backend_version(uint32 backend_version);
 extern bool contain_backend_version(uint32 version_number);
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index 9efd0343f..2daaa373a 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -68,6 +68,13 @@ typedef enum OptCompress {
     COMPRESS_HIGH,
 } OptCompress;
 
+/* How to handle rows that duplicate unique key values */
+typedef enum OnDuplicateAction {
+    DUPLICATE_ERROR = 0,
+    DUPLICATE_IGNORE,
+    DUPLICATE_REPLACE
+} OnDuplicate;
+
 /*
  * RangeVar - range variable, used in FROM clauses
  *
@@ -126,6 +133,9 @@ typedef struct IntoClause {
     struct DistributeBy* distributeby; /* distribution to use, or NULL */
     struct PGXCSubCluster* subcluster; /* subcluster node members */
 #endif
+    List* tableElts;         /* column definitions(list of ColumnDef) */
+    Node *autoIncStart; /* DefElem for AUTO_INCREMENT = value*/
+    OnDuplicateAction onduplicate;     /* how to handle rows that duplicate unique key values */
 } IntoClause;
 
 /* ----------------------------------------------------------------
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index 448b95814..503a42912 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -289,6 +289,7 @@ PG_KEYWORD("hour", HOUR_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("identified", IDENTIFIED, UNRESERVED_KEYWORD)
 PG_KEYWORD("identity", IDENTITY_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("if", IF_P, UNRESERVED_KEYWORD)
+PG_KEYWORD("ignore", IGNORE, UNRESERVED_KEYWORD)
 PG_KEYWORD("ignore_extra_data", IGNORE_EXTRA_DATA, UNRESERVED_KEYWORD)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD)
diff --git a/src/test/regress/expected/create_table.out b/src/test/regress/expected/create_table.out
index 79494b281..dc1e26a20 100644
--- a/src/test/regress/expected/create_table.out
+++ b/src/test/regress/expected/create_table.out
@@ -2191,3 +2191,220 @@ Options: orientation=row, compression=no
 
 drop table test_primary;
 \c postgres
+-- test mysql "create table as"
+-- a format
+create database a_createas dbcompatibility 'A';
+\c a_createas
+create table t_base(col1 int, col2 int, col3 int);
+create table t1 as select * from t_base;
+select * from t1;
+ col1 | col2 | col3 
+------+------+------
+(0 rows)
+
+create table t2(col) as select * from t_base;
+select * from t2;
+ col | col2 | col3 
+-----+------+------
+(0 rows)
+
+-- fail
+create table t3(col1,col2,col3,col4) as select * from t_base;
+ERROR:  CREATE TABLE AS specifies too many column names
+create table t4(col int) as select * from t_base;
+ERROR:  define column_definition is supported only in B-format database
+-- b format
+create database b_createas dbcompatibility 'B';
+\c b_createas
+create table t_base(col1 int, col2 int, col3 int);
+create table t1 as select * from t_base;
+select * from t1;
+ col1 | col2 | col3 
+------+------+------
+(0 rows)
+
+create table t2(col) as select * from t_base;
+select * from t2;
+ col | col2 | col3 
+-----+------+------
+(0 rows)
+
+create table t3(col int) as select * from t_base;
+select * from t3;
+ col | col1 | col2 | col3 
+-----+------+------+------
+(0 rows)
+
+create table t4(col1 int) as select * from t_base;
+select * from t4;
+ col1 | col2 | col3 
+------+------+------
+(0 rows)
+
+-- fail
+create table t5() as select * from t_base;
+ERROR:  syntax error at or near ")"
+LINE 1: create table t5() as select * from t_base;
+                        ^
+create table t6(col1 int) as select col1,* from t_base;
+ERROR:  column "col1" specified more than once
+LINE 1: create table t6(col1 int) as select col1,* from t_base;
+                                           ^
+-- duplicate key
+insert into t_base values(1,1,10),(1,2,9),(2,2,8),(2,1,7),(1,1,6);
+-- error
+create table t7(col1 int unique) as select * from t_base;
+NOTICE:  CREATE TABLE / UNIQUE will create implicit index "t7_col1_key" for table "t7"
+ERROR:  duplicate key value violates unique constraint "t7_col1_key"
+DETAIL:  Key (col1)=(1) already exists.
+-- ignore
+create table t8(col1 int unique) ignore as select * from t_base;
+NOTICE:  CREATE TABLE / UNIQUE will create implicit index "t8_col1_key" for table "t8"
+select * from t8;
+ col1 | col2 | col3 
+------+------+------
+    1 |    1 |   10
+    2 |    2 |    8
+(2 rows)
+
+-- replace
+create table t9(col1 int unique) replace as select * from t_base;
+NOTICE:  CREATE TABLE / UNIQUE will create implicit index "t9_col1_key" for table "t9"
+select * from t9 order by col3;
+ col1 | col2 | col3 
+------+------+------
+    1 |    1 |    6
+    2 |    1 |    7
+(2 rows)
+
+create table t10(col1 int unique, col2 int unique) replace as select * from t_base;
+NOTICE:  CREATE TABLE / UNIQUE will create implicit index "t10_col1_key" for table "t10"
+NOTICE:  CREATE TABLE / UNIQUE will create implicit index "t10_col2_key" for table "t10"
+select * from t10 order by col3;
+ col1 | col2 | col3 
+------+------+------
+    1 |    1 |    6
+(1 row)
+
+-- foreign key
+create table ftable(col int primary key);
+NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "ftable_pkey" for table "ftable"
+create table t11(col int, foreign key(col) references ftable(col)) as select * from t_base;
+ERROR:  CREATE TABLE AS SELECT is not allowed with Foreign Key
+create table t12(col int references ftable(col)) as select * from t_base;
+ERROR:  CREATE TABLE AS SELECT is not allowed with Foreign Key
+create table t13(foreign key(col1) references ftable(col)) as select * from t_base;
+ERROR:  CREATE TABLE AS SELECT is not allowed with Foreign Key
+-- table like
+create table t14(like t_base) as select * from t_base;
+ERROR:  CREATE TABLE AS SELECT is not allowed with Tablelike Clause
+-- with no data
+create table t15(id int, name char(8));
+insert into t15(id) select generate_series(1,10);
+create table t16(col1 int, id int) as select * from t15 where id with no data;
+select * from t16;
+ col1 | id | name 
+------+----+------
+(0 rows)
+
+create table t17(col1 int, id int unique) replace as select * from t15 where id with no data;
+NOTICE:  CREATE TABLE / UNIQUE will create implicit index "t17_id_key" for table "t17"
+select * from t17;
+ col1 | id | name 
+------+----+------
+(0 rows)
+
+-- union all
+create table test1(id int,name varchar(10),score numeric,date1 date,c1 bytea);
+insert into test1 values(1,'aaa',97.1,'1999-12-12','0101');
+insert into test1 values(5,'bbb',36.9,'1998-01-12','0110');
+insert into test1 values(30,'ooo',90.1,'2023-01-30','1001');
+insert into test1 values(6,'hhh',60,'2022-12-22','1010');
+insert into test1 values(7,'fff',71,'2001-11-23','1011');
+insert into test1 values(-1,'yaya',77.7,'2008-09-10','1100');
+insert into test1 values(7,'fff',71,'2001-11-23','1011');
+insert into test1 values(null,null,null,null,null);
+create table test2(id int,name varchar(10),score numeric,date1 date,c1 bytea);
+insert into test2 values(1,'aaa',99.1,'1998-12-12','0101');
+insert into test2 values(2,'hhh',36.9,'1996-01-12','0110');
+insert into test2 values(3,'ddd',89.2,'2000-03-12','0111');
+insert into test2 values(7,'uuu',60.9,'1997-01-01','1000');
+insert into test2 values(11,'eee',71,'2011-11-20','1011');
+insert into test2 values(-1,'yaya',76.7,'2008-09-10','1100');
+insert into test2 values(7,'uuu',60.9,'1997-01-01','1000');
+insert into test2 values(null,null,null,null,null);
+create table tb1(col1 int,id int) as select * from test1 where id<4 union all select * from test2 where score>80 order by id,score;
+select * from tb1 order by id;
+ col1 | id | name | score |   date1    |     c1     
+------+----+------+-------+------------+------------
+      | -1 | yaya |  77.7 | 09-10-2008 | \x31313030
+      |  1 | aaa  |  97.1 | 12-12-1999 | \x30313031
+      |  1 | aaa  |  99.1 | 12-12-1998 | \x30313031
+      |  3 | ddd  |  89.2 | 03-12-2000 | \x30313131
+(4 rows)
+
+create table tb2(col1 int,id int unique) replace as select * from test1 where id<4 union all select * from test2 where score>80 order by id,score;
+NOTICE:  CREATE TABLE / UNIQUE will create implicit index "tb2_id_key" for table "tb2"
+select * from tb2 order by id;
+ col1 | id | name | score |   date1    |     c1     
+------+----+------+-------+------------+------------
+      | -1 | yaya |  77.7 | 09-10-2008 | \x31313030
+      |  1 | aaa  |  99.1 | 12-12-1998 | \x30313031
+      |  3 | ddd  |  89.2 | 03-12-2000 | \x30313131
+(3 rows)
+
+-- test update
+create table tb_primary(a int primary key, b int);
+NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "tb_primary_pkey" for table "tb_primary"
+create table tb_unique(a int unique, b int);
+NOTICE:  CREATE TABLE / UNIQUE will create implicit index "tb_unique_a_key" for table "tb_unique"
+insert into tb_primary values(1,2),(2,4),(3,6);
+insert into tb_unique values(1,2),(2,4),(3,6);
+-- error
+insert into tb_primary values(1,1);
+ERROR:  duplicate key value violates unique constraint "tb_primary_pkey"
+DETAIL:  Key (a)=(1) already exists.
+insert into tb_unique values(1,1);
+ERROR:  duplicate key value violates unique constraint "tb_unique_a_key"
+DETAIL:  Key (a)=(1) already exists.
+-- UPDATE nothing
+insert into tb_primary values(1,1) ON DUPLICATE KEY UPDATE NOTHING;
+insert into tb_unique values(1,1) ON DUPLICATE KEY UPDATE NOTHING;
+select * from tb_primary;
+ a | b 
+---+---
+ 1 | 2
+ 2 | 4
+ 3 | 6
+(3 rows)
+
+select * from tb_unique;
+ a | b 
+---+---
+ 1 | 2
+ 2 | 4
+ 3 | 6
+(3 rows)
+
+-- UPDATE
+insert into tb_primary values(1,1) ON DUPLICATE KEY UPDATE a = 1, b = 1;
+insert into tb_unique values(1,1) ON DUPLICATE KEY UPDATE a = 1, b = 1;
+select * from tb_primary;
+ a | b 
+---+---
+ 2 | 4
+ 3 | 6
+ 1 | 1
+(3 rows)
+
+select * from tb_unique;
+ a | b 
+---+---
+ 2 | 4
+ 3 | 6
+ 1 | 1
+(3 rows)
+
+\c postgres
+drop database a_createas;
+drop database b_createas;
diff --git a/src/test/regress/sql/create_table.sql b/src/test/regress/sql/create_table.sql
index f3664446f..da650850d 100644
--- a/src/test/regress/sql/create_table.sql
+++ b/src/test/regress/sql/create_table.sql
@@ -1471,3 +1471,112 @@ create table test_primary(f11 int, f12 varchar(20), f13 bool, constraint con_t_p
 drop table test_primary;
 
 \c postgres
+-- test mysql "create table as"
+-- a format
+create database a_createas dbcompatibility 'A';
+\c a_createas
+
+create table t_base(col1 int, col2 int, col3 int);
+
+create table t1 as select * from t_base;
+select * from t1;
+create table t2(col) as select * from t_base;
+select * from t2;
+-- fail
+create table t3(col1,col2,col3,col4) as select * from t_base;
+create table t4(col int) as select * from t_base;
+
+-- b format
+create database b_createas dbcompatibility 'B';
+\c b_createas
+
+create table t_base(col1 int, col2 int, col3 int);
+
+create table t1 as select * from t_base;
+select * from t1;
+create table t2(col) as select * from t_base;
+select * from t2;
+create table t3(col int) as select * from t_base;
+select * from t3;
+create table t4(col1 int) as select * from t_base;
+select * from t4;
+
+-- fail
+create table t5() as select * from t_base;
+create table t6(col1 int) as select col1,* from t_base;
+
+-- duplicate key
+insert into t_base values(1,1,10),(1,2,9),(2,2,8),(2,1,7),(1,1,6);
+-- error
+create table t7(col1 int unique) as select * from t_base;
+-- ignore
+create table t8(col1 int unique) ignore as select * from t_base;
+select * from t8;
+-- replace
+create table t9(col1 int unique) replace as select * from t_base;
+select * from t9 order by col3;
+create table t10(col1 int unique, col2 int unique) replace as select * from t_base;
+select * from t10 order by col3;
+
+-- foreign key
+create table ftable(col int primary key);
+create table t11(col int, foreign key(col) references ftable(col)) as select * from t_base;
+create table t12(col int references ftable(col)) as select * from t_base;
+create table t13(foreign key(col1) references ftable(col)) as select * from t_base;
+-- table like
+create table t14(like t_base) as select * from t_base;
+
+-- with no data
+create table t15(id int, name char(8));
+insert into t15(id) select generate_series(1,10);
+create table t16(col1 int, id int) as select * from t15 where id with no data;
+select * from t16;
+create table t17(col1 int, id int unique) replace as select * from t15 where id with no data;
+select * from t17;
+
+-- union all
+create table test1(id int,name varchar(10),score numeric,date1 date,c1 bytea);
+insert into test1 values(1,'aaa',97.1,'1999-12-12','0101');
+insert into test1 values(5,'bbb',36.9,'1998-01-12','0110');
+insert into test1 values(30,'ooo',90.1,'2023-01-30','1001');
+insert into test1 values(6,'hhh',60,'2022-12-22','1010');
+insert into test1 values(7,'fff',71,'2001-11-23','1011');
+insert into test1 values(-1,'yaya',77.7,'2008-09-10','1100');
+insert into test1 values(7,'fff',71,'2001-11-23','1011');
+insert into test1 values(null,null,null,null,null);
+create table test2(id int,name varchar(10),score numeric,date1 date,c1 bytea);
+insert into test2 values(1,'aaa',99.1,'1998-12-12','0101');
+insert into test2 values(2,'hhh',36.9,'1996-01-12','0110');
+insert into test2 values(3,'ddd',89.2,'2000-03-12','0111');
+insert into test2 values(7,'uuu',60.9,'1997-01-01','1000');
+insert into test2 values(11,'eee',71,'2011-11-20','1011');
+insert into test2 values(-1,'yaya',76.7,'2008-09-10','1100');
+insert into test2 values(7,'uuu',60.9,'1997-01-01','1000');
+insert into test2 values(null,null,null,null,null);
+create table tb1(col1 int,id int) as select * from test1 where id<4 union all select * from test2 where score>80 order by id,score;
+select * from tb1 order by id;
+create table tb2(col1 int,id int unique) replace as select * from test1 where id<4 union all select * from test2 where score>80 order by id,score;
+select * from tb2 order by id;
+
+-- test update
+create table tb_primary(a int primary key, b int);
+create table tb_unique(a int unique, b int);
+insert into tb_primary values(1,2),(2,4),(3,6);
+insert into tb_unique values(1,2),(2,4),(3,6);
+-- error
+insert into tb_primary values(1,1);
+insert into tb_unique values(1,1);
+-- UPDATE nothing
+insert into tb_primary values(1,1) ON DUPLICATE KEY UPDATE NOTHING;
+insert into tb_unique values(1,1) ON DUPLICATE KEY UPDATE NOTHING;
+select * from tb_primary;
+select * from tb_unique;
+-- UPDATE
+insert into tb_primary values(1,1) ON DUPLICATE KEY UPDATE a = 1, b = 1;
+insert into tb_unique values(1,1) ON DUPLICATE KEY UPDATE a = 1, b = 1;
+select * from tb_primary;
+select * from tb_unique;
+
+\c postgres
+drop database a_createas;
+drop database b_createas;