*** a/src/backend/parser/parse_utilcmd.c
--- b/src/backend/parser/parse_utilcmd.c
***************
*** 298,303 **** transformColumnDefinition(CreateStmtContext *cxt, ColumnDef *column)
--- 298,304 ----
  	bool		saw_default;
  	Constraint *constraint;
  	ListCell   *clist;
+ 	int 		num_not_null;
  
  	cxt->columns = lappend(cxt->columns, column);
  
***************
*** 469,474 **** transformColumnDefinition(CreateStmtContext *cxt, ColumnDef *column)
--- 470,476 ----
  
  	saw_nullable = false;
  	saw_default = false;
+ 	num_not_null = 0;
  
  	foreach(clist, column->constraints)
  	{
***************
*** 478,487 **** transformColumnDefinition(CreateStmtContext *cxt, ColumnDef *column)
  		switch (constraint->contype)
  		{
  			case CONSTR_NULL:
! 				if (saw_nullable && column->is_not_null)
  					ereport(ERROR,
  							(errcode(ERRCODE_SYNTAX_ERROR),
! 							 errmsg("conflicting NULL/NOT NULL declarations for column \"%s\" of table \"%s\"",
  									column->colname, cxt->relation->relname),
  							 parser_errposition(cxt->pstate,
  												constraint->location)));
--- 480,489 ----
  		switch (constraint->contype)
  		{
  			case CONSTR_NULL:
! 				if (saw_nullable)
  					ereport(ERROR,
  							(errcode(ERRCODE_SYNTAX_ERROR),
! 							 errmsg("conflicting/multiple NULL/NOT NULL declarations for column \"%s\" of table \"%s\"",
  									column->colname, cxt->relation->relname),
  							 parser_errposition(cxt->pstate,
  												constraint->location)));
***************
*** 490,503 **** transformColumnDefinition(CreateStmtContext *cxt, ColumnDef *column)
  				break;
  
  			case CONSTR_NOTNULL:
! 				if (saw_nullable && !column->is_not_null)
  					ereport(ERROR,
  							(errcode(ERRCODE_SYNTAX_ERROR),
! 							 errmsg("conflicting NULL/NOT NULL declarations for column \"%s\" of table \"%s\"",
  									column->colname, cxt->relation->relname),
  							 parser_errposition(cxt->pstate,
  												constraint->location)));
  				column->is_not_null = TRUE;
  				saw_nullable = true;
  				break;
  
--- 492,515 ----
  				break;
  
  			case CONSTR_NOTNULL:
! 				/*
! 				 * Dont throw error for case tbl(id serial not null). For
! 				 * serial type, a NOT NULL constraint is implicitly added.
! 				 * So we should not stop user to give another NOT NULL.
! 				 * So in below check second part of condition is to handle
! 				 * this situation only.
! 				 */
! 				if (saw_nullable && (!is_serial || (!column->is_not_null ||
! 														num_not_null > 1)))
  					ereport(ERROR,
  							(errcode(ERRCODE_SYNTAX_ERROR),
! 							 errmsg("conflicting/multiple NULL/NOT NULL declarations for column \"%s\" of table \"%s\"",
  									column->colname, cxt->relation->relname),
  							 parser_errposition(cxt->pstate,
  												constraint->location)));
+ 
  				column->is_not_null = TRUE;
+ 				num_not_null++;
  				saw_nullable = true;
  				break;
  
***************
*** 1436,1441 **** transformIndexConstraints(CreateStmtContext *cxt)
--- 1448,1464 ----
  				index->deferrable == priorindex->deferrable &&
  				index->initdeferred == priorindex->initdeferred)
  			{
+ 				/*
+ 				 * Primary Key is considered to be explicit unique also, so
+ 				 * if user has given primary and unique both, then it should be
+ 				 * not be considered as repeatative unique constraints.
+ 				 */
+ 				if ((!priorindex->primary && !index->primary)
+ 									&& (priorindex->unique && index->unique))
+ 					ereport(ERROR,
+ 						(errcode(ERRCODE_SYNTAX_ERROR),
+ 						errmsg("multiple UNIQUE constraints for a column not allowed")));
+ 
  				priorindex->unique |= index->unique;
  
  				/*